51
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Kumar P, Muthu DVS, Harnagea L, Wurmehl S, Büchner B, Sood AK. Phonon anomalies, orbital-ordering and electronic raman scattering in iron-pnictide Ca(Fe0.97Co0.03)2As2: temperature-dependent Raman study. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2014; 26:305403. [PMID: 25008894 DOI: 10.1088/0953-8984/26/30/305403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
We report inelastic light scattering studies on Ca(Fe0.97Co0.03)2As2 in a wide spectral range of 120-5200 cm( - 1) from 5 to 300 K, covering the tetragonal to orthorhombic structural transition as well as magnetic transition at Tsm ~ 160 K. The mode frequencies of two first-order Raman modes B1g and Eg, both involving the displacement of Fe atoms, show a sharp increase below Tsm. Concomitantly, the linewidths of all the first-order Raman modes show anomalous broadening below Tsm, attributed to strong spin-phonon coupling. The high frequency modes observed between 400 and 1200 cm( - 1) are attributed to electronic Raman scattering involving the crystal field levels of d-orbitals of Fe(2+). The splitting between xz and yz d-orbital levels is shown to be ~25 meV, which increases as temperature decreases below Tsm. A broad Raman band observed at ~3200 cm( - 1) is assigned to two-magnon excitation of the itinerant Fe 3d antiferromagnet.
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Affiliation(s)
- Pradeep Kumar
- Department of Physics, Indian Institute of Science, Bangalore 560012, India
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52
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Chen X, Dai P, Feng D, Xiang T, Zhang FC. Iron-based high transition temperature superconductors. Natl Sci Rev 2014. [DOI: 10.1093/nsr/nwu007] [Citation(s) in RCA: 148] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Abstract
In a superconductor electrons form pairs and electric transport becomes dissipation-less at low temperatures. Recently discovered iron-based superconductors have the highest superconducting transition temperature next to copper oxides. In this article, we review material aspects and physical properties of iron-based superconductors. We discuss the dependence of transition temperature on the crystal structure, the interplay between antiferromagnetism and superconductivity by examining neutron scattering experiments, and the electronic properties of these compounds obtained by angle-resolved photoemission spectroscopy in link with some results from scanning tunneling microscopy/spectroscopy measurements. Possible microscopic model for this class of compounds is discussed from a strong coupling point of view.
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Affiliation(s)
- Xianhui Chen
- Department of Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Pengcheng Dai
- Department of Physics and Astronomy, Rice University, Houston, TX 77005, USA
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Donglai Feng
- Department of Physics, Fudan University, Shanghai 200433, China
| | - Tao Xiang
- Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Fu-Chun Zhang
- Department of Physics, Zhejiang University, Hangzhou, 310027, China
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53
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Kuo HH, Fisher IR. Effect of disorder on the resistivity anisotropy near the electronic nematic phase transition in pure and electron-doped BaFe(2)As(2). PHYSICAL REVIEW LETTERS 2014; 112:227001. [PMID: 24949785 DOI: 10.1103/physrevlett.112.227001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Indexed: 06/03/2023]
Abstract
We show that the strain-induced resistivity anisotropy in the tetragonal state of the representative underdoped Fe arsenides BaFe_{2}As_{2}, Ba(Fe_{1-x}Co_{x})_{2}As_{2} and Ba(Fe_{1-x}Ni_{x})_{2}As_{2} is independent of disorder over a wide range of defect and impurity concentrations. This result demonstrates that the anisotropy in the in-plane resistivity in the paramagnetic orthorhombic state of this material is not due to elastic scattering from anisotropic defects. Conversely, our result can be most easily understood if the resistivity anisotropy arises primarily from an intrinsic anisotropy in the electronic structure.
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Affiliation(s)
- Hsueh-Hui Kuo
- Geballe Laboratory for Advanced Materials and Department of Materials Science and Engineering, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
| | - Ian R Fisher
- Geballe Laboratory for Advanced Materials and Department of Applied Physics, Stanford University, Stanford, California 94305, USA and Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, USA
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54
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Cai P, Ruan W, Zhou X, Ye C, Wang A, Chen X, Lee DH, Wang Y. Doping dependence of the anisotropic quasiparticle interference in NaFe(1-x)Co(x)As iron-based superconductors. PHYSICAL REVIEW LETTERS 2014; 112:127001. [PMID: 24724672 DOI: 10.1103/physrevlett.112.127001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Indexed: 06/03/2023]
Abstract
We use scanning tunneling microscopy to investigate the doping dependence of quasiparticle interference (QPI) in NaFe1-xCoxAs iron-based superconductors. The goal is to study the relation between nematic fluctuations and Cooper pairing. In the parent and underdoped compounds, where fourfold rotational symmetry is broken macroscopically, the QPI patterns reveal strong rotational anisotropy. At optimal doping, however, the QPI patterns are always fourfold symmetric. We argue this implies small nematic susceptibility and, hence, insignificant nematic fluctuation in optimally doped iron pnictides. Since TC is the highest this suggests nematic fluctuation is not a prerequistite for strong Cooper pairing.
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Affiliation(s)
- Peng Cai
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
| | - Wei Ruan
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
| | - Xiaodong Zhou
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
| | - Cun Ye
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
| | - Aifeng Wang
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Xianhui Chen
- Hefei National Laboratory for Physical Science at Microscale and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, People's Republic of China
| | - Dung-Hai Lee
- Department of Physics, University of California at Berkeley, Berkeley, California 94720, USA and Materials Science Division, Lawrence Berkeley National Lab, Berkeley, California 94720, USA
| | - Yayu Wang
- State Key Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, People's Republic of China and Collaborative Innovation Center of Quantum Matter, Beijing 100084, People's Republic of China
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55
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Li G, Liang L, Li Q, Pan M, Nascimento VB, He X, Karki AB, Meunier V, Jin R, Zhang J, Plummer EW. Role of antiferromagnetic ordering in the (1×2) surface reconstruction of Ca(Fe(1-x)Co(x))2As2. PHYSICAL REVIEW LETTERS 2014; 112:077205. [PMID: 24579633 DOI: 10.1103/physrevlett.112.077205] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Indexed: 06/03/2023]
Abstract
Low energy electron diffraction, scanning tunneling microscopy and spectroscopy, and first-principles spin-dependent density functional theory are utilized to investigate the geometric, electronic, and magnetic structures of the stripe-ordered (1×2) surface of Ca(Fe1-xCox)2As2 (x=0, 0.075). The surface is terminated with a 50% Ca layer. Compared to the bulk, the surface Ca layer has a large inward relaxation (∼0.5 Å), and the underneath As-Fe2-As layer displays a significant buckling. First-principles calculations show that the (1×2) phase is stabilized by the bulk antiferromagnetic spin ordering through the spin-charge-lattice coupling. Strikingly, a superconducting gap (∼7 meV at 7.4 K) is observed to spatially coexist with the (1×2) phase (x=0.075 compound). This implies the coexistence of both superconductivity and AFM ordering at the surface.
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Affiliation(s)
- Guorong Li
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Liangbo Liang
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Qing Li
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - Minghu Pan
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
| | - V B Nascimento
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Xiaobo He
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - A B Karki
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Vincent Meunier
- Department of Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Rongying Jin
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - Jiandi Zhang
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | - E W Plummer
- Department of Physics & Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803, USA
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56
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Ma C, Wu L, Yin WG, Yang H, Shi H, Wang Z, Li J, Homes CC, Zhu Y. Strong coupling of the iron-quadrupole and anion-dipole polarizations in Ba(Fe(1-x)Co(x))2As2. PHYSICAL REVIEW LETTERS 2014; 112:077001. [PMID: 24579626 DOI: 10.1103/physrevlett.112.077001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Indexed: 06/03/2023]
Abstract
We use a quantitative convergent beam electron diffraction based method to image the valence electron density distribution in Ba(Fe1-xCox)2As2. We show a remarkable increase in both the charge quadrupole of the Fe cations and the charge dipole of the arsenic anions upon Co doping from x=0 (Tc=0 K) to x=0.1 (Tc=22.5 K). Our data suggest that an unexpected electronic correlation effect, namely strong coupling of Fe orbital fluctuation and anion electronic polarization, is present in iron-based superconductors.
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Affiliation(s)
- Chao Ma
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Lijun Wu
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Wei-Guo Yin
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Huaixin Yang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Honglong Shi
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhiwei Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jianqi Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - C C Homes
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - Yimei Zhu
- Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, New York 11973, USA
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57
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Gallais Y, Fernandes RM, Paul I, Chauvière L, Yang YX, Méasson MA, Cazayous M, Sacuto A, Colson D, Forget A. Observation of incipient charge nematicity in Ba(Fe(1-x)Co(x))2As2. PHYSICAL REVIEW LETTERS 2013; 111:267001. [PMID: 24483810 DOI: 10.1103/physrevlett.111.267001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2013] [Indexed: 06/03/2023]
Abstract
Using electronic Raman spectroscopy, we report direct measurements of charge nematic fluctuations in the tetragonal phase of strain-free Ba(Fe(1-x)Co(x))2As2 single crystals. The strong enhancement of the Raman response at low temperatures unveils an underlying charge nematic state that extends to superconducting compositions and which has hitherto remained unnoticed. Comparison between the extracted charge nematic susceptibility and the elastic modulus allows us to disentangle the charge contribution to the nematic instability, and to show that charge nematic fluctuations are weakly coupled to the lattice.
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Affiliation(s)
- Y Gallais
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - R M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, USA
| | - I Paul
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - L Chauvière
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - Y-X Yang
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - M-A Méasson
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - M Cazayous
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - A Sacuto
- Laboratoire Matériaux et Phénomenes Quantiques (UMR 7162 CNRS), Université Paris Diderot-Paris 7, Bâtiment Condorcet, 75205 Paris Cedex 13, France
| | - D Colson
- CEA-Saclay, IRAMIS, Service de Physique de l'Etat Condensé (SPEC URA CNRS 2464), F-91191 Gif-sur-Yvette, France
| | - A Forget
- CEA-Saclay, IRAMIS, Service de Physique de l'Etat Condensé (SPEC URA CNRS 2464), F-91191 Gif-sur-Yvette, France
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58
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Kim YK, Jung WS, Han GR, Choi KY, Chen CC, Devereaux TP, Chainani A, Miyawaki J, Takata Y, Tanaka Y, Oura M, Shin S, Singh AP, Lee HG, Kim JY, Kim C. Existence of orbital order and its fluctuation in superconducting Ba(Fe(1-x)Co(x))2As2 single crystals revealed by x-ray absorption spectroscopy. PHYSICAL REVIEW LETTERS 2013; 111:217001. [PMID: 24313517 DOI: 10.1103/physrevlett.111.217001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Indexed: 06/02/2023]
Abstract
We performed temperature dependent x-ray linear dichroism (XLD) experiments on an iron pnictide system, Ba(Fe(1-x)Co(x))2As2 with x=0.00, 0.05, 0.08, and 0.10 to experimentally verify the existence of orbital ordering (OO). Substantial XLD was observed in polarization dependent x-ray absorption spectra of Fe L edges. By exploiting the difference in the temperature dependent behaviors, OO, and structure contributions to XLD could be clearly separated. The observed OO signal indicates different occupation numbers for d(yz) and d(zx) orbitals and supports the existence of ferro-OO. The results are also consistent with the theoretical prediction. Moreover, we find substantial OO signal well above the structural and magnetic transition temperatures, which suggests the existence of strong OO fluctuations up to high temperatures.
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Affiliation(s)
- Y K Kim
- Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749, Korea
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59
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Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity. Proc Natl Acad Sci U S A 2013; 110:17623-30. [PMID: 24114268 DOI: 10.1073/pnas.1316512110] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron-electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron-electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electron-electron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs.
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60
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Fernandes RM, Böhmer AE, Meingast C, Schmalian J. Scaling between magnetic and lattice fluctuations in iron pnictide superconductors. PHYSICAL REVIEW LETTERS 2013; 111:137001. [PMID: 24116808 DOI: 10.1103/physrevlett.111.137001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/03/2013] [Revised: 08/05/2013] [Indexed: 06/02/2023]
Abstract
The phase diagram of the iron arsenides is dominated by a magnetic and a structural phase transition, which need to be suppressed in order for superconductivity to appear. The proximity between the two transition temperature lines indicates correlation between these two phases, whose nature remains unsettled. Here, we find a scaling relation between nuclear magnetic resonance and shear modulus data in the tetragonal phase of electron-doped Ba(Fe1-xCox)2As2 compounds. Because the former probes the strength of magnetic fluctuations while the latter is sensitive to orthorhombic fluctuations, our results provide strong evidence for a magnetically driven structural transition.
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Affiliation(s)
- Rafael M Fernandes
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55116, USA
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61
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Luo H, Wang M, Zhang C, Lu X, Regnault LP, Zhang R, Li S, Hu J, Dai P. Spin excitation anisotropy as a probe of orbital ordering in the paramagnetic tetragonal phase of superconducting BaFe1.904Ni0.09As2. PHYSICAL REVIEW LETTERS 2013; 111:107006. [PMID: 25166700 DOI: 10.1103/physrevlett.111.107006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Indexed: 06/03/2023]
Abstract
We use polarized neutron scattering to demonstrate that in-plane spin excitations in electron doped superconducting BaFe1.904Ni0.096As2 (Tc=19.8 K) change from isotropic to anisotropic in the tetragonal phase well above the antiferromagnetic (AFM) ordering and tetragonal-to-orthorhombic lattice distortion temperatures (TN≈Ts=33±2 K) without an uniaxial pressure. While the anisotropic spin excitations are not sensitive to the AFM order and tetragonal-to-orthorhombic lattice distortion, superconductivity induces further anisotropy for spin excitations along the [110] and [110] directions. These results indicate that the spin excitation anisotropy is a probe of the electronic anisotropy or orbital ordering in the tetragonal phase of iron pnictides.
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Affiliation(s)
- Huiqian Luo
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Meng Wang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Chenglin Zhang
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA and Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
| | - Xingye Lu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | | | - Rui Zhang
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shiliang Li
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jiangping Hu
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Department of Physics, Purdue University, West Lafayette, Indiana 47907, USA
| | - Pengcheng Dai
- Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China and Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA and Department of Physics and Astronomy, The University of Tennessee, Knoxville, Tennessee 37996-1200, USA
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62
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Alldredge JW, Calleja EM, Dai J, Eisaki H, Uchida S, McElroy K. The k-space origins of scattering in Bi2Sr2CaCu2O8+x. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2013; 25:335601. [PMID: 23883664 DOI: 10.1088/0953-8984/25/33/335601] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
We demonstrate a general, computer automated procedure that inverts the reciprocal space scattering data (q-space) that are measured by spectroscopic imaging scanning tunnelling microscopy (SI-STM) in order to determine the momentum space (k-space) scattering structure. This allows a detailed examination of the k-space origins of the quasiparticle interference (QPI) pattern in Bi2Sr2CaCu2O8+x within the theoretical constraints of the joint density of states (JDOS). Our new method allows measurement of the differences between the positive and negative energy dispersions, the gap structure and an energy dependent scattering length scale. Furthermore, it resolves the transition between the dispersive QPI and the checkerboard ([Formula: see text] excitation). We have measured the k-space scattering structure over a wide range of doping (p ∼ 0.22-0.08), including regions where the octet model is not applicable. Our technique allows the complete mapping of the k-space scattering origins of the spatial excitations in Bi2Sr2CaCu2O8+x, which allows for better comparisons between SI-STM and other experimental probes of the band structure. By applying our new technique to such a heavily studied compound, we can validate our new general approach for determining the k-space scattering origins from SI-STM data.
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63
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Ishida S, Nakajima M, Liang T, Kihou K, Lee CH, Iyo A, Eisaki H, Kakeshita T, Tomioka Y, Ito T, Uchida SI. Effect of Doping on the Magnetostructural Ordered Phase of Iron Arsenides: A Comparative Study of the Resistivity Anisotropy in Doped BaFe2As2 with Doping into Three Different Sites. J Am Chem Soc 2013; 135:3158-63. [DOI: 10.1021/ja311174e] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Shigeyuki Ishida
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Masamichi Nakajima
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Tian Liang
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Kunihiro Kihou
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Chul-Ho Lee
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Akira Iyo
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Hiroshi Eisaki
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Teruhisa Kakeshita
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Yasuhide Tomioka
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Toshimitsu Ito
- National Institute of Advanced Industrial Science and Technology, Tsukuba
305-8568, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
| | - Shin-ichi Uchida
- Department
of Physics, University of Tokyo, Tokyo
113-0033, Japan
- Transformative
Research Project
on Iron Pnictides, Japan Science and Technology Agency (JST), Tokyo 102-0075, Japan
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64
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Gretarsson H, Saha SR, Drye T, Paglione J, Kim J, Casa D, Gog T, Wu W, Julian SR, Kim YJ. Spin-state transition in the Fe pnictides. PHYSICAL REVIEW LETTERS 2013; 110:047003. [PMID: 25166195 DOI: 10.1103/physrevlett.110.047003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Indexed: 06/03/2023]
Abstract
We report an Fe Kβ x-ray emission spectroscopy study of local magnetic moments in the rare-earth doped iron pnictide Ca(1-x)RE(x)Fe(2)As(2) (RE = La, Pr, and Nd). In all samples studied the size of the Fe local moment is found to decrease significantly with temperature and goes from ∼ 0.9 μ(B) at T = 300 K to ∼ 0.45 μ(B) at T = 70 K. In the collapsed tetragonal phase of Nd- and Pr-doped samples (T<70 K) the local moment is quenched, while the moment remains unchanged for the La-doped sample, which does not show lattice collapse. Our results show that Ca(1-x)RE(x)Fe(2)As(2) (RE = Pr and Nd) exhibits a spin-state transition and provide direct evidence for a nonmagnetic Fe(2+) ion in the collapsed tetragonal phase; spin state as predicted by Yildirim. We argue that the gradual change of the spin state over a wide temperature range reveals the importance of multiorbital physics, in particular the competition between the crystal field split Fe 3d orbitals and the Hund's rule coupling.
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Affiliation(s)
- H Gretarsson
- Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada
| | - S R Saha
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - T Drye
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - J Paglione
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Jungho Kim
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - D Casa
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - T Gog
- Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA
| | - W Wu
- Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada
| | - S R Julian
- Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada
| | - Young-June Kim
- Department of Physics, University of Toronto, 60 Saint George Street, Toronto, Ontario M5S 1A7, Canada
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65
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Zeljkovic I, Hoffman JE. Interplay of chemical disorder and electronic inhomogeneity in unconventional superconductors. Phys Chem Chem Phys 2013; 15:13462-78. [DOI: 10.1039/c3cp51387d] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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66
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Yang H, Wang Z, Fang D, Deng Q, Wang QH, Xiang YY, Yang Y, Wen HH. In-gap quasiparticle excitations induced by non-magnetic Cu impurities in Na(Fe(0.96) Co(0.03)Cu(0.01))As revealed by scanning tunnelling spectroscopy. Nat Commun 2013; 4:2749. [PMID: 24248097 PMCID: PMC3868228 DOI: 10.1038/ncomms3749] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 10/10/2013] [Indexed: 11/08/2022] Open
Abstract
The origin of superconductivity in the iron pnictides remains unclear. One suggestion is that superconductivity in these materials has a magnetic origin, which would imply a sign-reversal s(±) pairing symmetry. Another suggests it is the result of orbital fluctuations, which would imply a sign-equal s(++) pairing symmetry. There is no consensus yet which of these two distinct and contrasting pairing symmetries is the right one in iron pnictide superconductors. Here we explore the nature of the pairing symmetry in the superconducting state of Na(Fe0.97-xCo0.03Cux)As by probing the effect of scattering of Cooper pairs by non-magnetic Cu impurities. Using scanning tunnelling spectroscopy, we identify the in-gap quasiparticle states induced by the Cu impurities, showing signatures of Cooper pair breaking by these non-magnetic impurities-a process that is only consistent with s(±) pairing. This experiment provides strong evidence for the s(±) pairing.
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Affiliation(s)
- Huan Yang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
- These authors contributed equally to this work
| | - Zhenyu Wang
- National Laboratory for Superconductivity, Institute of Physics and National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
- These authors contributed equally to this work
| | - Delong Fang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
- These authors contributed equally to this work
| | - Qiang Deng
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
| | - Qiang-Hua Wang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
| | - Yuan-Yuan Xiang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
| | - Yang Yang
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
| | - Hai-Hu Wen
- Center for Superconducting Physics and Materials, National Laboratory of Solid State Microstructures and Department of Physics, National Center of Microstructures and Quantum Manipulation, Nanjing University, Nanjing 210093, China
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67
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Arham HZ, Hunt CR, Park WK, Gillett J, Das SD, Sebastian SE, Xu ZJ, Wen JS, Lin ZW, Li Q, Gu G, Thaler A, Budko SL, Canfield PC, Greene LH. Gap-like feature in the normal state of X(Fe1−xCox)2As2, X = Ba, Sr and Fe1+yTe revealed by Point Contact Spectroscopy. ACTA ACUST UNITED AC 2012. [DOI: 10.1088/1742-6596/400/2/022001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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68
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Okazaki K, Ito Y, Ota Y, Kotani Y, Shimojima T, Kiss T, Watanabe S, Chen CT, Niitaka S, Hanaguri T, Takagi H, Chainani A, Shin S. Evidence for a cos(4φ) modulation of the superconducting energy gap of optimally doped FeTe(0.6)Se(0.4) single crystals using laser angle-resolved photoemission spectroscopy. PHYSICAL REVIEW LETTERS 2012; 109:237011. [PMID: 23368253 DOI: 10.1103/physrevlett.109.237011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2012] [Indexed: 06/01/2023]
Abstract
We study the superconducting-gap anisotropy of the Γ-centered hole Fermi surface in optimally doped FeTe(0.6)Se(0.4) (T(c)=14.5 K), using laser-excited angle-resolved photoemission spectroscopy. We observe sharp superconducting (SC) coherence peaks at T=2.5 K. In contrast to earlier angle-resolved photoemission spectroscopy studies but consistent with thermodynamic results, the momentum dependence shows a cos(4φ) modulation of the SC-gap anisotropy. The observed SC-gap anisotropy strongly indicates that the pairing interaction is not a conventional phonon-mediated isotropic one. Instead, the results suggest the importance of second-nearest-neighbor electronic interactions between the iron sites in the framework of s(±)-wave superconductivity.
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Affiliation(s)
- K Okazaki
- Institute for Solid State Physics (ISSP), University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
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69
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Nakajima M, Ishida S, Tomioka Y, Kihou K, Lee CH, Iyo A, Ito T, Kakeshita T, Eisaki H, Uchida S. Effect of Co doping on the in-plane anisotropy in the optical spectrum of underdoped Ba(Fe(1-x)Co(x))2As2. PHYSICAL REVIEW LETTERS 2012; 109:217003. [PMID: 23215609 DOI: 10.1103/physrevlett.109.217003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2012] [Indexed: 06/01/2023]
Abstract
We investigate the anisotropy in the in-plane optical spectra of detwinned Ba(Fe(1-x)Co(x))(2)As(2). The optical conductivity spectrum of BaFe(2)As(2) shows appreciable anisotropy in the magnetostructural ordered phase, whereas the dc (ω = 0) resistivity is nearly isotropic at low temperatures. Upon Co doping, the resistivity becomes highly anisotropic, while the finite-energy intrinsic anisotropy is suppressed. It is found that anisotropy in resistivity arises from anisotropic impurity scattering due to the presence of doped Co atoms, and it is extrinsic in origin. The intensity of a specific optical phonon mode is also found to show striking anisotropy in the ordered phase. The anisotropy induced by the Co impurity and that observed in the optical phonon mode are hallmarks of the highly polarizable electronic state in the ordered phase.
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Affiliation(s)
- M Nakajima
- Department of Physics, University of Tokyo, Tokyo 113-0033, Japan.
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70
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Singh DJ. Superconductivity and magnetism in 11-structure iron chalcogenides in relation to the iron pnictides. SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS 2012; 13:054304. [PMID: 27877517 PMCID: PMC5099618 DOI: 10.1088/1468-6996/13/5/054304] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/29/2012] [Accepted: 10/29/2012] [Indexed: 06/03/2023]
Abstract
This is a review of the magnetism and superconductivity in '11'-type Fe chalcogenides, as compared to the Fe-pnictide materials. The chalcogenides show many differences from the pnictides, as might be anticipated from their very varied chemistries. These differences include stronger renormalizations that might imply stronger correlation effects as well as different magnetic ordering patterns. Nevertheless the superconducting state and mechanism for superconductivity are apparently similar for the two classes of materials. Unanswered questions and challenges to theory are emphasized.
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Affiliation(s)
- David Joseph Singh
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831-6056, USA
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71
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Song CL, Wang YL, Jiang YP, Wang L, He K, Chen X, Hoffman JE, Ma XC, Xue QK. Suppression of superconductivity by twin boundaries in FeSe. PHYSICAL REVIEW LETTERS 2012; 109:137004. [PMID: 23030114 DOI: 10.1103/physrevlett.109.137004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Indexed: 06/01/2023]
Abstract
Low-temperature scanning tunneling microscopy and spectroscopy are employed to investigate twin boundaries in stoichiometric FeSe films grown by molecular beam epitaxy. Twin boundaries can be unambiguously identified by imaging the 90° change in the orientation of local electronic dimers from Fe site impurities on either side. Twin boundaries run at approximately 45° to the Fe-Fe bond directions, and noticeably suppress the superconducting gap, in contrast with the recent experimental and theoretical findings in other iron pnictides. Furthermore, vortices appear to accumulate on twin boundaries, consistent with the degraded superconductivity there. The variation in superconductivity is likely caused by the increased Se height in the vicinity of twin boundaries, providing the first local evidence for the importance of this height to the mechanism of superconductivity.
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Affiliation(s)
- Can-Li Song
- State Key Laboratory for Surface Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
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72
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Koepernik K, Johnston S, van Heumen E, Huang Y, Kaas J, Goedkoop JB, Golden MS, van den Brink J. Surface adatom conductance filtering in scanning tunneling spectroscopy of co-doped BaFe2As2 iron pnictide superconductors. PHYSICAL REVIEW LETTERS 2012; 109:127001. [PMID: 23005977 DOI: 10.1103/physrevlett.109.127001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2012] [Indexed: 06/01/2023]
Abstract
We establish in a combination of ab initio theory and experiments that the tunneling process in scanning tunneling microscopy or spectroscopy on the A-122 iron pnictide superconductors-in this case BaFe(2-x)Co(x)As(2)-involves a strong adatom filtering of the differential conductance from the near-E(F) Fe-3d states, which in turn originates from the topmost subsurface Fe layer of the crystal. The calculations show that the dominance of surface Ba-related tunneling pathways leaves fingerprints found in the experimental differential conductance data, including large particle-hole asymmetry and energy-dependent contrast inversion in conductance maps.
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Affiliation(s)
- K Koepernik
- Institute for Theoretical Solid State Physics, IFW Dresden, Germany
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73
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Chu JH, Kuo HH, Analytis JG, Fisher IR. Divergent Nematic Susceptibility in an Iron Arsenide Superconductor. Science 2012; 337:710-2. [DOI: 10.1126/science.1221713] [Citation(s) in RCA: 402] [Impact Index Per Article: 33.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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74
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Liang S, Alvarez G, Şen C, Moreo A, Dagotto E. Anisotropy of electrical transport in pnictide superconductors studied using Monte Carlo simulations of the spin-fermion model. PHYSICAL REVIEW LETTERS 2012; 109:047001. [PMID: 23006104 DOI: 10.1103/physrevlett.109.047001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Indexed: 06/01/2023]
Abstract
An undoped three-orbital spin-fermion model for the Fe-based superconductors is studied via Monte Carlo techniques in two-dimensional clusters. At low temperatures, the magnetic and one-particle spectral properties are in agreement with neutron and photoemission experiments. Our main results are the resistance versus temperature curves that display the same features observed in BaFe(2)As(2) detwinned single crystals (under uniaxial stress), including a low-temperature anisotropy between the two directions followed by a peak at the magnetic ordering temperature, that qualitatively appears related to short-range spin order and concomitant Fermi surface orbital order.
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Affiliation(s)
- Shuhua Liang
- Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
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75
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Ruff JPC, Chu JH, Kuo HH, Das RK, Nojiri H, Fisher IR, Islam Z. Susceptibility anisotropy in an iron arsenide superconductor revealed by x-ray diffraction in pulsed magnetic fields. PHYSICAL REVIEW LETTERS 2012; 109:027004. [PMID: 23030198 DOI: 10.1103/physrevlett.109.027004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Indexed: 06/01/2023]
Abstract
In addition to unconventional high-T(c) superconductivity, the iron arsenides exhibit strong magnetoelastic coupling and a notable electronic anisotropy within the a-b plane. We relate these properties by studying underdoped Ba(Fe(1-x)Co(x))2As2 by x-ray diffraction in pulsed magnetic fields up to 27.5 T. We exploit magnetic detwinning effects to demonstrate anisotropy in the in-plane susceptibility, which develops at the structural phase transition despite the absence of magnetic order. The degree of detwinning increases smoothly with decreasing temperature, and a single-domain condition is realized over a range of field and temperature. At low temperatures we observe an activated behavior, with a large hysteretic remnant effect. Detwinning was not observed within the superconducting phase for accessible magnetic fields.
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Affiliation(s)
- J P C Ruff
- The Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
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76
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Electronic nematicity above the structural and superconducting transition in BaFe2(As(1-x)P(x))2. Nature 2012; 486:382-5. [PMID: 22722198 DOI: 10.1038/nature11178] [Citation(s) in RCA: 369] [Impact Index Per Article: 30.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 05/01/2012] [Indexed: 11/08/2022]
Abstract
Electronic nematicity, a unidirectional self-organized state that breaks the rotational symmetry of the underlying lattice, has been observed in the iron pnictide and copper oxide high-temperature superconductors. Whether nematicity plays an equally important role in these two systems is highly controversial. In iron pnictides, the nematicity has usually been associated with the tetragonal-to-orthorhombic structural transition at temperature T(s). Although recent experiments have provided hints of nematicity, they were performed either in the low-temperature orthorhombic phase or in the tetragonal phase under uniaxial strain, both of which break the 90° rotational C(4) symmetry. Therefore, the question remains open whether the nematicity can exist above T(s) without an external driving force. Here we report magnetic torque measurements of the isovalent-doping system BaFe(2)(As(1-x)P(x))(2), showing that the nematicity develops well above T(s) and, moreover, persists to the non-magnetic superconducting regime, resulting in a phase diagram similar to the pseudogap phase diagram of the copper oxides. By combining these results with synchrotron X-ray measurements, we identify two distinct temperatures-one at T*, signifying a true nematic transition, and the other at T(s) (<T*), which we show not to be a true phase transition, but rather what we refer to as a 'meta-nematic transition', in analogy to the well-known meta-magnetic transition in the theory of magnetism.
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77
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Park T, Lee H, Martin I, Lu X, Sidorov VA, Gofryk K, Ronning F, Bauer ED, Thompson JD. Textured superconducting phase in the heavy fermion CeRhIn5. PHYSICAL REVIEW LETTERS 2012; 108:077003. [PMID: 22401243 DOI: 10.1103/physrevlett.108.077003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 05/31/2023]
Abstract
When antiferromagnetism and unconventional superconductivity coexist in CeRhIn(5) there is a significant temperature difference between resistively and thermodynamically determined transitions into the superconducting state. In this state, anisotropic transport near the superconducting transition reveals the emergence of textured superconducting planes that appear without a change in translational symmetry of the lattice. CeRhIn(5) is not unique in exhibiting these behaviors, indicating that textured superconductivity may be a general consequence of coexisting orders in correlated electron materials.
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Affiliation(s)
- Tuson Park
- Department of Physics, Sungkyunkwan University, Suwon, Korea
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78
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Trinckauf J, Hänke T, Zabolotnyy V, Ritschel T, Apostu MO, Suryanarayanan R, Revcolevschi A, Koepernik K, Kim TK, Zimmermann MV, Borisenko SV, Knupfer M, Büchner B, Geck J. Electronic confinement and ordering instabilities in colossal magnetoresistive bilayer manganites. PHYSICAL REVIEW LETTERS 2012; 108:016403. [PMID: 22304275 DOI: 10.1103/physrevlett.108.016403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2011] [Revised: 09/16/2011] [Indexed: 05/31/2023]
Abstract
We present angle-resolved photoemission studies of (La{1-z}Pr{z}){2-2x}Sr{1+2x}Mn{2}O{7} with x=0.4 and z=0.1, 0.2, and 0.4 along with density functional theory calculations and x-ray scattering data. Our results show that the bilayer splitting in the ferromagnetic metallic phase of these materials is small, if not completely absent. The charge carriers are therefore confined to a single MnO{2} layer, which in turn results in a strongly nested Fermi surface. In addition to this, the spectral function also displays clear signatures of an electronic ordering instability well below the Fermi level. The increase of the corresponding interaction strength with z and its magnitude of ∼400 meV make the coupling to a bare phonon highly unlikely. Instead we conclude that fluctuating order, involving electronic and lattice degrees of freedom, causes the observed renormalization of the spectral features.
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Affiliation(s)
- J Trinckauf
- Leibniz Institute for Solid State and Materials Research IFW Dresden, Helmholtzstraße 20, 01069 Dresden, Germany
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79
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Fernandes RM, Abrahams E, Schmalian J. Anisotropic in-plane resistivity in the nematic phase of the iron pnictides. PHYSICAL REVIEW LETTERS 2011; 107:217002. [PMID: 22181914 DOI: 10.1103/physrevlett.107.217002] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Indexed: 05/31/2023]
Abstract
We show that the interference between scattering by impurities and by critical spin fluctuations gives rise to anisotropic transport in the Ising-nematic state of the iron pnictides. The effect is closely related to the non-Fermi-liquid behavior of the resistivity near an antiferromagnetic quantum critical point. Our theory not only explains the observed sign of the resistivity anisotropy Δρ in electron-doped systems but also predicts a sign change of Δρ upon sufficient hole doping. Furthermore, our model naturally addresses the changes in Δρ upon sample annealing and alkaline-earth substitution.
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Affiliation(s)
- Rafael M Fernandes
- Ames Laboratory, Department of Physics and Astronomy, Iowa State University, 50011, USA
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80
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Mayorov AS, Elias DC, Mucha-Kruczynski M, Gorbachev RV, Tudorovskiy T, Zhukov A, Morozov SV, Katsnelson MI, Geim AK, Novoselov KS. Interaction-Driven Spectrum Reconstruction in Bilayer Graphene. Science 2011; 333:860-3. [DOI: 10.1126/science.1208683] [Citation(s) in RCA: 236] [Impact Index Per Article: 18.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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81
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Ying JJ, Wang XF, Wu T, Xiang ZJ, Liu RH, Yan YJ, Wang AF, Zhang M, Ye GJ, Cheng P, Hu JP, Chen XH. Measurements of the anisotropic in-plane resistivity of underdoped FeAs-based pnictide superconductors. PHYSICAL REVIEW LETTERS 2011; 107:067001. [PMID: 21902359 DOI: 10.1103/physrevlett.107.067001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/13/2010] [Indexed: 05/31/2023]
Abstract
We systematically investigated the in-plane resistivity anisotropy of electron-underdoped EuFe(2-x)Co(x)As(2) and BaFe(2-x)Co(x)As(2) and hole-underdoped Ba(1-x)K(x)Fe(2)As(2). Large in-plane resistivity anisotropy was found in the former samples, while tiny in-plane resistivity anisotropy was detected in the latter ones. When it is detected, the anisotropy starts above the structural transition temperature and increases smoothly through it. As the temperature is lowered further, the anisotropy takes a dramatic enhancement through the magnetic transition temperature. We found that the anisotropy is universally tied to the presence of T-linear behavior of resistivity. Our results demonstrate that the nematic state is caused by electronic degrees of freedom, and the microscopic orbital involvement in the magnetically ordered state must be fundamentally different between the hole- and electron-doped materials.
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Affiliation(s)
- J J Ying
- Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Anhui, People's Republic of China
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82
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Malavasi L, Artioli GA, Kim H, Maroni B, Joseph B, Ren Y, Proffen T, Billinge SJL. Local structural investigation of SmFeAsO₁₋xF(x) high temperature superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2011; 23:272201. [PMID: 21659693 DOI: 10.1088/0953-8984/23/27/272201] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
A strong revitalization of the field of high temperature superconductivity (HTSC) has been induced recently by the discovery of T(C) around 26 K in F-doped LaFeAsO iron pnictides. Starting from this discovery, a huge amount of experimental data have been accumulated. This important corpus of results will allow the development of suitable theoretical models aimed at describing the basic electronic structure properties and nature of superconducting states in these fascinating new systems. A close correlation between structural features and physical properties of the normal and superconducting states has already been demonstrated in the current literature. Advanced theoretical models are also based on the close correlation with structural properties and in particular with the Fe-As tetrahedral array. As for other complex materials, a deeper understanding of their structure-properties correlation requires a full knowledge of the atomic arrangement within the structure. Here we report an investigation of the local structure in the SmFeAsO₁₋ xF(x) system carried out by means of x-ray total scattering measurements and pair distribution function analysis. The results presented indicate that the local structure of these HTSC significantly differs from the average structure determined by means of traditional diffraction techniques, in particular the distribution of Fe-As bond lengths. In addition, a model for describing the observed discrepancies is presented.
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Affiliation(s)
- Lorenzo Malavasi
- Dipartimento di Chimica-Sezione di Chimica Fisica, INSTM (UdR Pavia), Università di Pavia, Viale Taramelli 16, 27100 Pavia, Italy
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83
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Unprecedented anisotropic metallic state in undoped iron arsenide BaFe2As2 revealed by optical spectroscopy. Proc Natl Acad Sci U S A 2011; 108:12238-42. [PMID: 21746905 DOI: 10.1073/pnas.1100102108] [Citation(s) in RCA: 168] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
An ordered phase showing remarkable electronic anisotropy in proximity to the superconducting phase is now a hot issue in the field of high-transition-temperature superconductivity. As in the case of copper oxides, superconductivity in iron arsenides competes or coexists with such an ordered phase. Undoped and underdoped iron arsenides have a magnetostructural ordered phase exhibiting stripe-like antiferromagnetic spin order accompanied by an orthorhombic lattice distortion; both the spin order and lattice distortion break the tetragonal symmetry of crystals of these compounds. In this ordered state, anisotropy of in-plane electrical resistivity is anomalous and difficult to attribute simply to the spin order and/or the lattice distortion. Here, we present the anisotropic optical spectra measured on detwinned BaFe(2)As(2) crystals with light polarization parallel to the Fe planes. Pronounced anisotropy is observed in the spectra, persisting up to an unexpectedly high photon energy of about 2 eV. Such anisotropy arises from an anisotropic energy gap opening below and slightly above the onset of the order. Detailed analysis of the optical spectra reveals an unprecedented electronic state in the ordered phase.
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84
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Carlson E, Dahmen K. Using disorder to detect locally ordered electron nematics via hysteresis. Nat Commun 2011; 2:379. [DOI: 10.1038/ncomms1375] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Accepted: 06/03/2011] [Indexed: 11/09/2022] Open
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85
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Maldonado A, Guillamón I, Suderow H, Vieira S. Scanning tunneling spectroscopy under large current flow through the sample. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2011; 82:073710. [PMID: 21806192 DOI: 10.1063/1.3615627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We describe a method to make scanning tunneling microscopy/spectroscopy imaging at very low temperatures while driving a constant electric current up to some tens of mA through the sample. It gives a new local probe, which we term current driven scanning tunneling microscopy/spectroscopy. We show spectroscopic and topographic measurements under the application of a current in superconducting Al and NbSe(2) at 100 mK. Perspective of applications of this local imaging method includes local vortex motion experiments, and Doppler shift local density of states studies.
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Affiliation(s)
- A Maldonado
- Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Facultad de Ciencias, Universidad Autónoma de Madrid, 28049 Madrid, Spain
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86
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Localization of electrons due to orbitally ordered bi-stripes in the bilayer manganite La(2-2x)Sr(1+2x)Mn2O7 (x ~ 0.59). Proc Natl Acad Sci U S A 2011; 108:11799-803. [PMID: 21715662 DOI: 10.1073/pnas.1018604108] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Electronic phases with stripe patterns have been intensively investigated for their vital roles in unique properties of correlated electronic materials. How these real-space patterns affect the conductivity and other properties of materials (which are usually described in momentum space) is one of the major challenges of modern condensed matter physics. By studying the electronic structure of La(2-2x)Sr(1+2x)Mn(2)O(7) (x ∼ 0.59) and in combination with earlier scattering measurements, we demonstrate the variation of electronic properties accompanying the melting of so-called bi-stripes in this material. The static bi-stripes can strongly localize the electrons in the insulating phase above T(c) ∼ 160 K, while the fraction of mobile electrons grows, coexisting with a significant portion of localized electrons when the static bi-stripes melt below T(c). The presence of localized electrons below T(c) suggests that the melting bi-stripes exist as a disordered or fluctuating counterpart. From static to melting, the bi-stripes act as an atomic-scale electronic valve, leading to a "colossal" metal-insulator transition in this material.
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87
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Song CL, Wang YL, Cheng P, Jiang YP, Li W, Zhang T, Li Z, He K, Wang L, Jia JF, Hung HH, Wu C, Ma X, Chen X, Xue QK. Direct Observation of Nodes and Twofold Symmetry in FeSe Superconductor. Science 2011; 332:1410-3. [DOI: 10.1126/science.1202226] [Citation(s) in RCA: 333] [Impact Index Per Article: 25.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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88
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Yi M, Lu D, Chu JH, Analytis JG, Sorini AP, Kemper AF, Moritz B, Mo SK, Moore RG, Hashimoto M, Lee WS, Hussain Z, Devereaux TP, Fisher IR, Shen ZX. Symmetry-breaking orbital anisotropy observed for detwinned Ba(Fe 1-xCo x) 2As 2 above the spin density wave transition. Proc Natl Acad Sci U S A 2011; 108:6878-6883. [PMCID: PMC3084148 DOI: 10.1073/pnas.1015572108] [Citation(s) in RCA: 115] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/30/2024] Open
Abstract
Nematicity, defined as broken rotational symmetry, has recently been observed in competing phases proximate to the superconducting phase in the cuprate high-temperature superconductors. Similarly, the new iron-based high-temperature superconductors exhibit a tetragonal-to-orthorhombic structural transition (i.e., a broken C4 symmetry) that either precedes or is coincident with a collinear spin density wave (SDW) transition in undoped parent compounds, and superconductivity arises when both transitions are suppressed via doping. Evidence for strong in-plane anisotropy in the SDW state in this family of compounds has been reported by neutron scattering, scanning tunneling microscopy, and transport measurements. Here, we present an angle-resolved photoemission spectroscopy study of detwinned single crystals of a representative family of electron-doped iron-arsenide superconductors, Ba(Fe1-x Cox )2As2 in the underdoped region. The crystals were detwinned via application of in-plane uniaxial stress, enabling measurements of single domain electronic structure in the orthorhombic state. At low temperatures, our results clearly demonstrate an in-plane electronic anisotropy characterized by a large energy splitting of two orthogonal bands with dominant d xz and d yz character, which is consistent with anisotropy observed by other probes. For compositions x > 0, for which the structural transition (T S ) precedes the magnetic transition (T SDW), an anisotropic splitting is observed to develop above T SDW, indicating that it is specifically associated with T S . For unstressed crystals, the band splitting is observed close to T S , whereas for stressed crystals, the splitting is observed to considerably higher temperatures, revealing the presence of a surprisingly large in-plane nematic susceptibility in the electronic structure.
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Affiliation(s)
- Ming Yi
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
| | - Donghui Lu
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025; and
| | - Jiun-Haw Chu
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
| | - James G. Analytis
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
| | - Adam P. Sorini
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
| | - Alexander F. Kemper
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
| | - Brian Moritz
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
| | - Sung-Kwan Mo
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Rob G. Moore
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
| | - Makoto Hashimoto
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Wei-Sheng Lee
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
| | - Zahid Hussain
- Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, CA 94720
| | - Thomas P. Devereaux
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
| | - Ian R. Fisher
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
| | - Zhi-Xun Shen
- Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025
- Geballe Laboratory for Advanced Materials, Departments of Physics and Applied Physics, Stanford University, Stanford, CA 94305
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89
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Teague ML, Drayna GK, Lockhart GP, Cheng P, Shen B, Wen HH, Yeh NC. Measurement of a sign-changing two-gap superconducting phase in electron-doped Ba(Fe(1-x)Co(x))2As2 single crystals using scanning tunneling spectroscopy. PHYSICAL REVIEW LETTERS 2011; 106:087004. [PMID: 21405593 DOI: 10.1103/physrevlett.106.087004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2010] [Indexed: 05/30/2023]
Abstract
Scanning tunneling spectroscopic studies of Ba(Fe(1-x)Co(x))(2)As(2) (x=0.06, 0.12) single crystals reveal direct evidence for predominantly two-gap superconductivity. These gaps decrease with increasing temperature and vanish above the superconducting transition T(c). The two-gap nature and the slightly doping- and energy-dependent quasiparticle scattering interferences near the wave vectors (±π, 0) and (0, ±π) are consistent with sign-changing s-wave superconductivity. The excess zero-bias conductance and the large gap-to-T(c) ratios suggest dominant unitary impurity scattering.
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Affiliation(s)
- M L Teague
- Department of Physics, California Institute of Technology, Pasadena, California 91125, USA
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90
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Zhou X, Ye C, Cai P, Wang X, Chen X, Wang Y. Quasiparticle interference of C2-symmetric surface states in a LaOFeAs parent compound. PHYSICAL REVIEW LETTERS 2011; 106:087001. [PMID: 21405590 DOI: 10.1103/physrevlett.106.087001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Indexed: 05/30/2023]
Abstract
We present scanning tunneling microscopy studies of the LaOFeAs parent compound of iron pnictide superconductors. High resolution spectroscopic imaging reveals strong standing wave patterns induced by quasiparticle interference of two-dimensional surface states. Fourier analysis shows that the distribution of scattering wave vectors exhibits pronounced twofold (C(2)) symmetry, strongly reminiscent of the nematic electronic state found in CaFe(1.94)Co(0.06)As(2). The implications of these results to the electronic structure of the pnictide parent states will be discussed.
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Affiliation(s)
- Xiaodong Zhou
- Laboratory of Low Dimensional Quantum Physics, Department of Physics, Tsinghua University, Haidian, Beijing 100084, People's Republic of China
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91
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van Heumen E, Vuorinen J, Koepernik K, Massee F, Huang Y, Shi M, Klei J, Goedkoop J, Lindroos M, van den Brink J, Golden MS. Existence, character, and origin of surface-related bands in the high temperature iron pnictide superconductor BaFe(2-x)Co(x)As2. PHYSICAL REVIEW LETTERS 2011; 106:027002. [PMID: 21405247 DOI: 10.1103/physrevlett.106.027002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/17/2010] [Indexed: 05/30/2023]
Abstract
Low energy electron diffraction (LEED) experiments, LEED simulations, and finite slab density functional calculations are combined to study the cleavage surface of Co doped BaFe(2-x)Co(x)As2 (x = 0.1,0.17). We demonstrate that the energy dependence of the LEED data can only be understood from a terminating 1/2 Ba layer accompanied by distortions of the underlying As-Fe2-As block. As a result, surface-related Fe 3d states are present in the electronic structure, which we identify in angle resolved photoemission spectroscopy (ARPES) experiments. The close proximity of the surface-related states to the bulk bands inevitably leads to broadening of the ARPES signals, which excludes the use of the BaFe(2-x)Co(x)As2 system for accurate determination of self-energies using ARPES.
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Affiliation(s)
- Erik van Heumen
- van der Waals-Zeeman institute, University of Amsterdam, 1018 XL Amsterdam, The Netherlands.
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92
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Bozin ES, Malliakas CD, Souvatzis P, Proffen T, Spaldin NA, Kanatzidis MG, Billinge SJL. Entropically Stabilized Local Dipole Formation in Lead Chalcogenides. Science 2010; 330:1660-3. [DOI: 10.1126/science.1192759] [Citation(s) in RCA: 269] [Impact Index Per Article: 19.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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93
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Valenzuela B, Bascones E, Calderón MJ. Conductivity anisotropy in the antiferromagnetic state of iron pnictides. PHYSICAL REVIEW LETTERS 2010; 105:207202. [PMID: 21231260 DOI: 10.1103/physrevlett.105.207202] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/28/2010] [Revised: 09/15/2010] [Indexed: 05/30/2023]
Abstract
Recent experiments on iron pnictides have uncovered a large in-plane resistivity anisotropy with a surprising result: The system conducts better in the antiferromagnetic x direction than in the ferromagnetic y direction. We address this problem by calculating the ratio of the Drude weight along the x and y directions, D(x)/D(y), for the mean-field Q=(π,0) magnetic phase diagram of a five-band model for the undoped pnictides. We find that D(x)/D(y) ranges between 0.2<D(x)/D(y)<1.7 for different interaction parameters. Large values of the orbital ordering favor an anisotropy opposite to the one found experimentally. On the other hand, D(x)/D(y) is strongly dependent on the topology and morphology of the reconstructed Fermi surface. Our results point against orbital ordering as the origin of the observed conductivity anisotropy, which may be ascribed to the anisotropy of the Fermi velocity.
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Affiliation(s)
- B Valenzuela
- Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, E-28049 Madrid, Spain.
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94
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Fernandes RM, VanBebber LH, Bhattacharya S, Chandra P, Keppens V, Mandrus D, McGuire MA, Sales BC, Sefat AS, Schmalian J. Effects of nematic fluctuations on the elastic properties of iron arsenide superconductors. PHYSICAL REVIEW LETTERS 2010; 105:157003. [PMID: 21230930 DOI: 10.1103/physrevlett.105.157003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2009] [Indexed: 05/30/2023]
Abstract
We demonstrate that the changes in the elastic properties of the FeAs systems, as seen in our resonant ultrasound spectroscopy data, can be naturally understood in terms of fluctuations of emerging nematic degrees of freedom. Both the softening of the lattice in the normal, tetragonal phase as well as its hardening in the superconducting phase are consistently described by our model. Our results confirm the view that structural order is induced by magnetic fluctuations.
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Affiliation(s)
- R M Fernandes
- Ames Laboratory and Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011, USA.
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95
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Yin WG, Lee CC, Ku W. Unified picture for magnetic correlations in iron-based superconductors. PHYSICAL REVIEW LETTERS 2010; 105:107004. [PMID: 20867542 DOI: 10.1103/physrevlett.105.107004] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Indexed: 05/29/2023]
Abstract
The varying metallic antiferromagnetic correlations observed in iron-based superconductors are unified in a model consisting of both itinerant electrons and localized spins. The decisive factor is found to be the sensitive competition between the superexchange antiferromagnetism and the orbital-degenerate double-exchange ferromagnetism. Our results reveal the crucial role of Hund's rule coupling for the strongly correlated nature of the system and suggest that the iron-based superconductors are closer kin to manganites than cuprates in terms of their diverse magnetism and incoherent normal-state electron transport. This unified picture would be instrumental for exploring other exotic properties and the mechanism of superconductivity in this new class of superconductors.
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Affiliation(s)
- Wei-Guo Yin
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA.
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96
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Lawler MJ, Fujita K, Lee J, Schmidt AR, Kohsaka Y, Kim CK, Eisaki H, Uchida S, Davis JC, Sethna JP, Kim EA. Intra-unit-cell electronic nematicity of the high-T(c) copper-oxide pseudogap states. Nature 2010; 466:347-51. [PMID: 20631795 DOI: 10.1038/nature09169] [Citation(s) in RCA: 159] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2010] [Accepted: 05/04/2010] [Indexed: 11/10/2022]
Abstract
In the high-transition-temperature (high-T(c)) superconductors the pseudogap phase becomes predominant when the density of doped holes is reduced. Within this phase it has been unclear which electronic symmetries (if any) are broken, what the identity of any associated order parameter might be, and which microscopic electronic degrees of freedom are active. Here we report the determination of a quantitative order parameter representing intra-unit-cell nematicity: the breaking of rotational symmetry by the electronic structure within each CuO(2) unit cell. We analyse spectroscopic-imaging scanning tunnelling microscope images of the intra-unit-cell states in underdoped Bi(2)Sr(2)CaCu(2)O(8 +) (delta) and, using two independent evaluation techniques, find evidence for electronic nematicity of the states close to the pseudogap energy. Moreover, we demonstrate directly that these phenomena arise from electronic differences at the two oxygen sites within each unit cell. If the characteristics of the pseudogap seen here and by other techniques all have the same microscopic origin, this phase involves weak magnetic states at the O sites that break 90 degrees -rotational symmetry within every CuO(2) unit cell.
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Affiliation(s)
- M J Lawler
- Department of Physics, Applied Physics and Astronomy, Binghamton University, Binghamton, New York 13902-6000, USA
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97
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Chu JH, Analytis JG, De Greve K, McMahon PL, Islam Z, Yamamoto Y, Fisher IR. In-plane resistivity anisotropy in an underdoped iron arsenide superconductor. Science 2010; 329:824-6. [PMID: 20705856 DOI: 10.1126/science.1190482] [Citation(s) in RCA: 180] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
High-temperature superconductivity often emerges in the proximity of a symmetry-breaking ground state. For superconducting iron arsenides, in addition to the antiferromagnetic ground state, a small structural distortion breaks the crystal's C(4 )rotational symmetry in the underdoped part of the phase diagram. We reveal that the representative iron arsenide Ba(Fe(1)(-x)Co(x))(2)As(2) develops a large electronic anisotropy at this transition via measurements of the in-plane resistivity of detwinned single crystals, with the resistivity along the shorter b axis rho(b) being greater than rho(a). The anisotropy reaches a maximum value of ~2 for compositions in the neighborhood of the beginning of the superconducting dome. For temperatures well above the structural transition, uniaxial stress induces a resistivity anisotropy, indicating a substantial nematic susceptibility.
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Affiliation(s)
- Jiun-Haw Chu
- Department of Applied Physics and Geballe Laboratory for Advanced Materials, Stanford University, Stanford, CA 94305, USA
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98
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Knolle J, Eremin I, Akbari A, Moessner R. Quasiparticle interference in the spin-density wave phase of iron-based superconductors. PHYSICAL REVIEW LETTERS 2010; 104:257001. [PMID: 20867410 DOI: 10.1103/physrevlett.104.257001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Indexed: 05/29/2023]
Abstract
We propose an explanation for the electronic nematic state observed recently in parent iron-based superconductors [T.-M. Chuang, Science 327, 181 (2010)10.1126/science.1181083]. We argue that the quasi-one-dimensional nanostructure identified in the quasiparticle interference (QPI) is a consequence of the interplay of the magnetic (π, 0) spin-density wave (SDW) order with the underlying electronic structure. We show that the evolution of the QPI peaks largely reflects quasiparticle scattering between bands involved in the SDW formation. Because of the ellipticity of the electron pocket and the fact that only one of the electron pockets is involved in the SDW, the resulting QPI has a pronounced one-dimensional structure. We further predict that the QPI crosses over to two dimensionality on an energy scale, set by the SDW gap.
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Affiliation(s)
- J Knolle
- Max Planck Institute for the Physics of Complex Systems, D-01187 Dresden, Germany
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99
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Bascones E, Calderón MJ, Valenzuela B. Low magnetization and anisotropy in the antiferromagnetic state of undoped iron pnictides. PHYSICAL REVIEW LETTERS 2010; 104:227201. [PMID: 20867201 DOI: 10.1103/physrevlett.104.227201] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Revised: 05/07/2010] [Indexed: 05/29/2023]
Abstract
We examine the magnetic phase diagram of iron pnictides using a five-band model. For the intermediate values of the interaction expected to hold in the iron pnictides, we find a metallic low moment state characterized by antiparallel orbital magnetic moments. The anisotropy of the interorbital hopping amplitudes is the key to understanding this low moment state. This state accounts for the small magnetization measured in undoped iron pnictides and leads to the strong exchange anisotropy found in neutron experiments. Orbital ordering is concomitant with magnetism and produces the large zx orbital weight seen at Γ in photoemission experiments.
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Affiliation(s)
- E Bascones
- Instituto de Ciencia de Materiales de Madrid, ICMM-CSIC, Cantoblanco, E-28049 Madrid, Spain.
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100
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Tranquada J. Modulated superfluid density in an iron-pnictide superconductor. PHYSICS 2010. [DOI: 10.1103/physics.3.41] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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