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Abstract
AbstractA long-standing theoretical prediction is that in clean, nodal unconventional superconductors the magnetic penetration depth λ, at zero temperature, varies linearly with magnetic field. This non-linear Meissner effect is an equally important manifestation of the nodal state as the well studied linear-in-T dependence of λ, but has never been convincingly experimentally observed. Here we present measurements of the nodal superconductors CeCoIn5 and LaFePO which clearly show this non-linear Meissner effect. We further show how the effect of a small dc magnetic field on λ(T) can be used to distinguish gap nodes from non-nodal deep gap minima. Our measurements of KFe2As2 suggest that this material has such a non-nodal state.
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Ghimire S, Kończykowski M, Cho K, Tanatar MA, Torsello D, Veshchunov IS, Tamegai T, Ghigo G, Prozorov R. Effect of Controlled Artificial Disorder on the Magnetic Properties of EuFe 2(As 1-xP x) 2 Ferromagnetic Superconductor. MATERIALS (BASEL, SWITZERLAND) 2021; 14:3267. [PMID: 34199183 PMCID: PMC8231935 DOI: 10.3390/ma14123267] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Revised: 06/09/2021] [Accepted: 06/09/2021] [Indexed: 11/17/2022]
Abstract
Static (DC) and dynamic (AC, at 14 MHz and 8 GHz) magnetic susceptibilities of single crystals of a ferromagnetic superconductor, EuFe2(As1-xPx)2 (x = 0.23), were measured in pristine state and after different doses of 2.5 MeV electron or 3.5 MeV proton irradiation. The superconducting transition temperature, Tc(H), shows an extraordinarily large decrease. It starts at Tc(H=0)≈24K in the pristine sample for both AC and DC measurements, but moves to almost half of that value after moderate irradiation dose. Remarkably, after the irradiation not only Tc moves significantly below the FM transition, its values differ drastically for measurements at different frequencies, ≈16 K in AC measurements and ≈12 K in a DC regime. We attribute such a large difference in Tc to the appearance of the spontaneous internal magnetic field below the FM transition, so that the superconductivity develops directly into the mixed spontaneous vortex-antivortex state where the onset of diamagnetism is known to be frequency-dependent. We also examined the response to the applied DC magnetic fields and studied the annealing of irradiated samples, which almost completely restores the superconducting transition. Overall, our results suggest that in EuFe2(As1-xPx)2 superconductivity is affected by local-moment ferromagnetism mostly via the spontaneous internal magnetic fields induced by the FM subsystem. Another mechanism is revealed upon irradiation where magnetic defects created in ordered Eu2+ lattice act as efficient pairbreakers leading to a significant Tc reduction upon irradiation compared to other 122 compounds. On the other hand, the exchange interactions seem to be weakly screened by the superconducting phase leading to a modest increase of Tm (less than 1 K) after the irradiation drives Tc to below Tm. Our results suggest that FM and SC phases coexist microscopically in the same volume.
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Affiliation(s)
- Sunil Ghimire
- Ames Laboratory, Ames, IA 50011, USA; (S.G.); (K.C.); (M.A.T.)
- Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
| | - Marcin Kończykowski
- Laboratoire des Solides Irradiés, CEA/DRF/lRAMIS, École Polytechnique, CNRS, Institut Polytechnique de Paris, F-91128 Palaiseau, France;
| | - Kyuil Cho
- Ames Laboratory, Ames, IA 50011, USA; (S.G.); (K.C.); (M.A.T.)
| | - Makariy A. Tanatar
- Ames Laboratory, Ames, IA 50011, USA; (S.G.); (K.C.); (M.A.T.)
- Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
| | - Daniele Torsello
- Politecnico di Torino, Department of Applied Science and Technology, 10129 Torino, Italy; (D.T.); (G.G.)
- Istituto Nazionale di Fisica Nucleare, Sezione di Torino, 10125 Torino, Italy
| | - Ivan S. Veshchunov
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; (I.S.V.); (T.T.)
| | - Tsuyoshi Tamegai
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan; (I.S.V.); (T.T.)
| | - Gianluca Ghigo
- Politecnico di Torino, Department of Applied Science and Technology, 10129 Torino, Italy; (D.T.); (G.G.)
- Istituto Nazionale di Fisica Nucleare, Sezione di Torino, 10125 Torino, Italy
| | - Ruslan Prozorov
- Ames Laboratory, Ames, IA 50011, USA; (S.G.); (K.C.); (M.A.T.)
- Department of Physics & Astronomy, Iowa State University, Ames, IA 50011, USA
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Takenaka T, Ishihara K, Roppongi M, Miao Y, Mizukami Y, Makita T, Tsurumi J, Watanabe S, Takeya J, Yamashita M, Torizuka K, Uwatoko Y, Sasaki T, Huang X, Xu W, Zhu D, Su N, Cheng JG, Shibauchi T, Hashimoto K. Strongly correlated superconductivity in a copper-based metal-organic framework with a perfect kagome lattice. SCIENCE ADVANCES 2021; 7:7/12/eabf3996. [PMID: 33731356 PMCID: PMC7968839 DOI: 10.1126/sciadv.abf3996] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/29/2021] [Indexed: 05/26/2023]
Abstract
Metal-organic frameworks (MOFs), which are self-assemblies of metal ions and organic ligands, provide a tunable platform to search a new state of matter. A two-dimensional (2D) perfect kagome lattice, whose geometrical frustration is a key to realizing quantum spin liquids, has been formed in the π - d conjugated 2D MOF [Cu3(C6S6)] n (Cu-BHT). The recent discovery of its superconductivity with a critical temperature T c of 0.25 kelvin raises fundamental questions about the nature of electron pairing. Here, we show that Cu-BHT is a strongly correlated unconventional superconductor with extremely low superfluid density. A nonexponential temperature dependence of superfluid density is observed, indicating the possible presence of superconducting gap nodes. The magnitude of superfluid density is much smaller than those in conventional superconductors and follows the Uemura's relation of strongly correlated superconductors. These results imply that the unconventional superconductivity in Cu-BHT originates from electron correlations related to spin fluctuations of kagome lattice.
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Affiliation(s)
- T Takenaka
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - K Ishihara
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - M Roppongi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Y Miao
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Y Mizukami
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - T Makita
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - J Tsurumi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - S Watanabe
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - J Takeya
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - M Yamashita
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - K Torizuka
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Department of Physics, Nippon Institute of Technology, Miyashiro, Saitama 345-8501, Japan
| | - Y Uwatoko
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - T Sasaki
- Institute for Materials Research, Tohoku University, Aoba-ku, Sendai 980-8577, Japan
| | - X Huang
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - W Xu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - D Zhu
- Beijing National Laboratory for Molecular Sciences, Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China
| | - N Su
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - J-G Cheng
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
| | - K Hashimoto
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
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Wu TC, Pal HK, Hosur P, Foster MS. Power-Law Temperature Dependence of the Penetration Depth in a Topological Superconductor Due to Surface States. PHYSICAL REVIEW LETTERS 2020; 124:067001. [PMID: 32109094 DOI: 10.1103/physrevlett.124.067001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Accepted: 01/27/2020] [Indexed: 06/10/2023]
Abstract
We study the temperature dependence of the magnetic penetration depth in a 3D topological superconductor (TSC), incorporating the paramagnetic current due to the surface states. A TSC is predicted to host a gapless 2D surface Majorana fluid. In addition to the bulk-dominated London response, we identify a T^{3} power-law-in-temperature contribution from the surface, valid in the low-temperature limit. Our system is fully gapped in the bulk, and should be compared to bulk nodal superconductivity, which also exhibits power-law behavior. Power-law temperature dependence of the penetration depth can be one indicator of topological superconductivity.
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Affiliation(s)
- Tsz Chun Wu
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
| | - Hridis K Pal
- Department of Physics, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - Pavan Hosur
- Texas Center for Superconductivity and Department of Physics, University of Houston, Houston, Texas 77204, USA
| | - Matthew S Foster
- Department of Physics and Astronomy, Rice University, Houston, Texas 77005, USA
- Rice Center for Quantum Materials, Rice University, Houston, Texas 77005, USA
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Takenaka T, Mizukami Y, Wilcox JA, Konczykowski M, Seiro S, Geibel C, Tokiwa Y, Kasahara Y, Putzke C, Matsuda Y, Carrington A, Shibauchi T. Full-Gap Superconductivity Robust against Disorder in Heavy-Fermion CeCu_{2}Si_{2}. PHYSICAL REVIEW LETTERS 2017; 119:077001. [PMID: 28949698 DOI: 10.1103/physrevlett.119.077001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Indexed: 06/07/2023]
Abstract
A key aspect of unconventional pairing by the antiferromagnetic spin-fluctuation mechanism is that the superconducting energy gap must have the opposite sign on different parts of the Fermi surface. Recent observations of non-nodal gap structure in the heavy-fermion superconductor CeCu_{2}Si_{2} were then very surprising, given that this material has long been considered a prototypical example of a superconductor where the Cooper pairing is magnetically mediated. Here we present a study of the effect of controlled point defects, introduced by electron irradiation, on the temperature-dependent magnetic penetration depth λ(T) in CeCu_{2}Si_{2}. We find that the fully gapped state is robust against disorder, demonstrating that low-energy bound states, expected for sign-changing gap structures, are not induced by nonmagnetic impurities. This provides bulk evidence for s_{++}-wave superconductivity without sign reversal.
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Affiliation(s)
- T Takenaka
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - Y Mizukami
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
| | - J A Wilcox
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, England
| | - M Konczykowski
- Laboratoire des Solides Irradiés, École Polytechnique, CNRS, CEA, Université Paris-Saclay, F-91128 Palaiseau, France
| | - S Seiro
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
- Institute for Solid State Physics, IFW-Dresden, Helmholtzstrasse 20, 01069 Dresden, Germany
| | - C Geibel
- Max Planck Institute for Chemical Physics of Solids, 01187 Dresden, Germany
| | - Y Tokiwa
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
- Center for Electronic Correlations and Magnetism, Institute of Physics, Augsburg University, 86159 Augsburg, Germany
| | - Y Kasahara
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - C Putzke
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, England
| | - Y Matsuda
- Department of Physics, Kyoto University, Kyoto 606-8502, Japan
| | - A Carrington
- H. H. Wills Physics Laboratory, University of Bristol, Bristol BS8 1TL, England
| | - T Shibauchi
- Department of Advanced Materials Science, University of Tokyo, Kashiwa, Chiba 277-8561, Japan
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Jiao L, Weng Z, Liu J, Zhang J, Pang G, Guo C, Gao F, Zhu X, Wen HH, Yuan HQ. Evidence for nodeless superconductivity in NdO(1-x)F(x)BiS2 (x = 0.3 and 0.5) single crystals. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:225701. [PMID: 25988300 DOI: 10.1088/0953-8984/27/22/225701] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We study the superconducting pairing states of NdO(1-x)F(x)BiS2 (x = 0.3 and 0.5) by measuring the magnetic penetration depth Δλ(T) using the tunnel-diode-oscillator (TDO) technique. An upturn is observed in Δλ(T) as well as the magnetic susceptibility χ(T) in the low-temperature limit, which is attributed to the paramagnetism of Nd ions. After subtracting the paramagnetic contributions, the penetration depth Δλ(T) follows an exponential-type temperature dependence at T ≪ T(c), providing evidence of nodeless superconductivity for NdO(1-x)F(x)BiS2. This is further supported by the analyses of superfluid density ρ(s)(T), which can be well described by a BCS model with an energy gap of Δ(0) ∼ 2.15 k(B)T(c).
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Affiliation(s)
- Lin Jiao
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou, Zhejiang 310058, People's Republic of China
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Mizukami Y, Konczykowski M, Kawamoto Y, Kurata S, Kasahara S, Hashimoto K, Mishra V, Kreisel A, Wang Y, Hirschfeld PJ, Matsuda Y, Shibauchi T. Disorder-induced topological change of the superconducting gap structure in iron pnictides. Nat Commun 2014; 5:5657. [PMID: 25430419 DOI: 10.1038/ncomms6657] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Accepted: 10/24/2014] [Indexed: 11/09/2022] Open
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8
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Martin C, Tillman ME, Kim H, Tanatar MA, Kim SK, Kreyssig A, Gordon RT, Vannette MD, Nandi S, Kogan VG, Bud'ko SL, Canfield PC, Goldman AI, Prozorov R. Nonexponential London penetration depth of FeAs-based superconducting RFeAsO(0.9)F(0.1) (R = La, Nd) single crystals. PHYSICAL REVIEW LETTERS 2009; 102:247002. [PMID: 19659038 DOI: 10.1103/physrevlett.102.247002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2009] [Indexed: 05/28/2023]
Abstract
The superconducting penetration depth lambda(T) has been measured in RFeAsO(0.9)F(0.1) (R = La, Nd) single crystals (R-1111). In Nd-1111, we find an upturn in lambda(T) upon cooling and attribute it to the paramagnetism of the Nd ions, similar to the case of the electron-doped cuprate Nd-Ce-Cu-O. After the correction for paramagnetism, the London penetration depth variation is found to follow a power-law behavior, Deltalambda_{L}(T) proportional, variantT;{2} at low temperatures. The same T2 variation of lambda(T) was found in nonmagnetic La-1111 crystals. Analysis of the superfluid density and of penetration depth anisotropy over the full temperature range is consistent with two-gap superconductivity. Based on this and on our previous work, we conclude that both the RFeAsO (1111) and BaFe(2)As(2) (122) families of pnictide superconductors exhibit unconventional two-gap superconductivity.
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Affiliation(s)
- C Martin
- Ames Laboratory and Department of Physics & Astronomy, Iowa State University, Ames, Iowa 50011, USA
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Hashimoto K, Shibauchi T, Kato T, Ikada K, Okazaki R, Shishido H, Ishikado M, Kito H, Iyo A, Eisaki H, Shamoto S, Matsuda Y. Microwave penetration depth and quasiparticle conductivity of PrFeAsO1-y single crystals: evidence for a full-gap superconductor. PHYSICAL REVIEW LETTERS 2009; 102:017002. [PMID: 19257228 DOI: 10.1103/physrevlett.102.017002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Indexed: 05/27/2023]
Abstract
In-plane microwave penetration depth lambda_{ab} and quasiparticle conductivity at 28 GHz are measured in underdoped single crystals of the Fe-based superconductor PrFeAsO_{1-y} (T_{c} approximately 35 K) by using a sensitive superconducting cavity resonator. lambda_{ab}(T) shows flat dependence at low temperatures, which is incompatible with the presence of nodes in the superconducting gap Delta(k). The temperature dependence of the superfluid density demonstrates that the gap is nonzero (Delta/k_{B}T_{c} greater, similar1.6) all over the Fermi surface. The microwave conductivity below T_{c} exhibits an enhancement larger than the coherence peak, reminiscent of high-T_{c} cuprate superconductors.
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Affiliation(s)
- K Hashimoto
- Department of Physics, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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Das T, Markiewicz RS, Bansil A. Nodeless d-wave superconducting pairing due to residual antiferromagnetism in underdoped Pr2-xCexCuO4-delta. PHYSICAL REVIEW LETTERS 2007; 98:197004. [PMID: 17677653 DOI: 10.1103/physrevlett.98.197004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Indexed: 05/16/2023]
Abstract
We investigate the doping dependence of the penetration depth versus temperature in electron-doped Pr(2-x)Ce(x)CuO(4-delta) using a model which assumes the uniform coexistence of (mean-field) antiferromagnetism and superconductivity. Despite the presence of a d(x2-y2) pairing gap in the underlying spectrum, we find nodeless behavior of the low-T penetration depth in the underdoped case, in accord with experimental results. As doping increases, a linear-in-T behavior of the penetration depth, characteristic of d-wave pairing, emerges as the lower magnetic band crosses the Fermi level and creates a nodal Fermi surface pocket.
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Affiliation(s)
- Tanmoy Das
- Physics Department, Northeastern University, Boston, MA 02115, USA
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Prozorov R, Lawrie DD, Hetel I, Fournier P, Giannetta RW. Field-dependent diamagnetic transition in magnetic superconductor Sm1.85Ce0.15CuO4-y. PHYSICAL REVIEW LETTERS 2004; 93:147001. [PMID: 15524829 DOI: 10.1103/physrevlett.93.147001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2004] [Indexed: 05/24/2023]
Abstract
The magnetic penetration depth of single crystal Sm(1.85)Ce(0.15)CuO(4-y) was measured down to 0.4 K in dc fields up to 7 kOe. For insulating Sm2CuO4, Sm3+ spins order at the Ne el temperature, T(N)=6 K, independent of the applied field. Superconducting Sm(1.85)Ce(0.15)CuO(4-y) (T(c) approximately 23 K) shows a sharp increase in diamagnetic screening below T(*)(H) which varied from 4.0 K (H=0) to 0.5 K (H=7 kOe) for a field along the c axis. If the field was aligned parallel to the conducting planes, T(*) remained unchanged. The unusual field dependence of T(*) indicates a spin-freezing transition that dramatically increases the superfluid density.
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Affiliation(s)
- R Prozorov
- Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA
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Snezhko A, Prozorov R, Lawrie DD, Giannetta RW, Gauthier J, Renaud J, Fournier P. Nodal order parameter in electron-doped Pr(2-x)CexCuO(4-delta) superconducting films. PHYSICAL REVIEW LETTERS 2004; 92:157005. [PMID: 15169311 DOI: 10.1103/physrevlett.92.157005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2003] [Indexed: 05/24/2023]
Abstract
The London penetration depth, lambda(ab)(T), is reported for thin films of the electron-doped superconductor Pr(2-x)Ce(x)CuO(4-delta) with varying Ce concentration, x=0.13, 0.15, and 0.17. Measurements down to 0.35 K were carried out using a tunnel-diode oscillator with excitation fields applied both perpendicular and parallel to the conducting planes. Films at all three doping levels exhibited power law behavior indicative of d-wave pairing with impurity scattering. These results are fully consistent with previous measurements on single crystals.
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Affiliation(s)
- A Snezhko
- Department of Physics & Astronomy and NanoCenter, University of South Carolina, 712 Main Street, Columbia, South Carolina 29208, USA
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Sonier JE, Poon KF, Luke GM, Kyriakou P, Miller RI, Liang R, Wiebe CR, Fournier P, Greene RL. Superconductivity and field-induced magnetism in Pr2-xCexCuO4 single crystals. PHYSICAL REVIEW LETTERS 2003; 91:147002. [PMID: 14611547 DOI: 10.1103/physrevlett.91.147002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/11/2003] [Indexed: 05/24/2023]
Abstract
We report muon-spin rotation and relaxation (muSR) measurements on single crystals of the electron-doped high-T(c) superconductor Pr2-xCexCuO4. In a zero external magnetic field, superconductivity is found to coexist with dilute Cu spins that are static on the muSR time scale. In an applied field, we observe a mu(+)-Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T(c), an additional source of local magnetic field appears throughout the volume of the sample. This finding is shown to be consistent with field-induced antiferromagnetic ordering of the Cu spins. Measurements of the temperature dependence of the in-plane magnetic penetration depth lambda(ab) in the vortex state are also presented.
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Affiliation(s)
- J E Sonier
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Zheng GQ, Sato T, Kitaoka Y, Fujita M, Yamada K. Fermi-liquid ground state in the n-type Pr(0.91)LaCe(0.09)CuO(4-y) copper-oxide superconductor. PHYSICAL REVIEW LETTERS 2003; 90:197005. [PMID: 12785976 DOI: 10.1103/physrevlett.90.197005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/28/2002] [Indexed: 05/24/2023]
Abstract
We report nuclear magnetic resonance studies on the low-doped n-type copper-oxide Pr(0.91)LaCe(0.09)CuO(4-y) (T(c)=24 K) in the superconducting state and in the normal state uncovered by the application of a strong magnetic field. We find that when the superconductivity is removed the underlying ground state is the Fermi liquid state. This result is at variance with that inferred from previous thermal conductivity measurement and appears to contrast with that in p-type copper oxides with a similar doping level where high-T(c) superconductivity sets in within the pseudogap phase. The data in the superconducting state are consistent with the line-node gap model.
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Affiliation(s)
- Guo-qing Zheng
- Department of Physical Science, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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Biswas A, Fournier P, Qazilbash MM, Smolyaninova VN, Balci H, Greene RL. Evidence of a d- to s-wave pairing symmetry transition in the electron-doped cuprate superconductor Pr(2-x)CexCuO4. PHYSICAL REVIEW LETTERS 2002; 88:207004. [PMID: 12005593 DOI: 10.1103/physrevlett.88.207004] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2001] [Indexed: 05/23/2023]
Abstract
We present point contact spectroscopy (PCS) data for junctions between a normal metal and the electron-doped cuprate superconductor Pr(2-x)CexCuO4 (PCCO). For the underdoped compositions of this cuprate ( x approximately 0.13) we observe a peak in the conductance-voltage characteristics of the point contact junctions. The shape and magnitude of this peak suggest the presence of Andreev bound states at the surface of underdoped PCCO which is evidence for a d-wave pairing symmetry. For overdoped PCCO ( x approximately 0.17) the PCS data do not show any evidence of Andreev bound states at the surface suggesting an s-wave pairing symmetry.
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Affiliation(s)
- Amlan Biswas
- Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742
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Armitage NP, Lu DH, Feng DL, Kim C, Damascelli A, Shen KM, Ronning F, Shen ZX, Onose Y, Taguchi Y, Tokura Y. Superconducting gap anisotropy in Nd1.85Ce0.15CuO4: results from photoemission. PHYSICAL REVIEW LETTERS 2001; 86:1126-1129. [PMID: 11178026 DOI: 10.1103/physrevlett.86.1126] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2000] [Indexed: 05/23/2023]
Abstract
We have performed angle resolved photoelectron spectroscopy on the electron doped cuprate superconductor Nd1.85Ce0.15CuO4. A comparison of the leading edge midpoints between the superconducting and normal states reveals a small, but finite shift of 1.5-2 meV near the ( pi,0) position, but no observable shift along the zone diagonal near ( pi/2, pi/2). This is interpreted as evidence for an anisotropic superconducting gap in the electron doped materials, which is consistent with the presence of d-wave superconducting order in this cuprate superconductor.
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Affiliation(s)
- N P Armitage
- Department of Physics, Applied Physics and Stanford Synchrotron Radiation Laboratory, Stanford University, Stanford, California 94305, USA
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Carrington A, Manzano F, Prozorov R, Giannetta RW, Kameda N, Tamegai T. Evidence for surface Andreev bound states in cuprate superconductors from penetration depth measurements. PHYSICAL REVIEW LETTERS 2001; 86:1074-1077. [PMID: 11178013 DOI: 10.1103/physrevlett.86.1074] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2000] [Indexed: 05/23/2023]
Abstract
Tunneling and theoretical studies have suggested that Andreev bound states form at certain surfaces of unconventional superconductors. Through studies of the temperature and field dependence of the in-plane magnetic penetration depth lambda(ab) at low temperature, we have found strong evidence for the presence of these states in clean single crystal YBCO and BSCCO. Crystals cut to expose (110) surfaces show a strong upturn in lambda(ab) at around 7 K, when the field is oriented along the c axis. In YBCO this upturn is completely suppressed by a field of approximately 0.1 T.
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Affiliation(s)
- A Carrington
- Department of Physics and Astronomy, University of Leeds, United Kingdom
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Prozorov R, Giannetta RW, Fournier P, Greene RL. Evidence for nodal quasiparticles in electron-doped cuprates from penetration depth measurements. PHYSICAL REVIEW LETTERS 2000; 85:3700-3703. [PMID: 11030985 DOI: 10.1103/physrevlett.85.3700] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2000] [Indexed: 05/23/2023]
Abstract
The in-plane magnetic penetration depth, lambda(T), was measured down to 0.4 K in single crystals of electron-doped superconductors, Pr(1.85)Ce(0.15)CuO(4-delta) (PCCO) and Nd(1.85)Ce(0.15)CuO(4-delta) (NCCO). In PCCO, the superfluid density varies as T2 from 0.025 up to roughly 0.3T/T(c) suggestive of a d-wave state with impurities. In NCCO, lambda(T) shows a pronounced upturn for T<4 K due to the paramagnetic contribution of Nd3+ ions. Fits to an s-wave order parameter over the standard BCS range (T/T(c) = 0.32) limit any gap to less than Delta(min)(0)/T(c) = 0.57 in NCCO. For PCCO, the absence of paramagnetism permits a lower temperature fit and yields an upper limit of Delta(min)(0)/T(c) = 0.2.
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Affiliation(s)
- R Prozorov
- Loomis Laboratory of Physics, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801, USA
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Kokales JD, Fournier P, Mercaldo LV, Talanov VV, Greene RL, Anlage SM. Microwave electrodynamics of electron-doped cuprate superconductors. PHYSICAL REVIEW LETTERS 2000; 85:3696-3699. [PMID: 11030984 DOI: 10.1103/physrevlett.85.3696] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/18/2000] [Indexed: 05/23/2023]
Abstract
We report microwave cavity perturbation measurements of the temperature dependence of the penetration depth, lambda(T), and conductivity, sigma(T) of Pr(2-x)Ce(x)CuO(4-delta) (PCCO) crystals, as well as parallel-plate resonator measurements of lambda(T) in PCCO thin films. Penetration depth measurements are also presented for a Nd(2-x)Ce(x)CuO(4-delta) (NCCO) crystal. We find that Deltalambda(T) has a power-law behavior for T<T(c)/3, and conclude that the electron-doped cuprate superconductors have nodes in the superconducting gap. Furthermore, using the surface impedance, we have derived the real part of the conductivity, sigma(1)(T), below T(c) and found a behavior similar to that observed in hole-doped cuprates.
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Affiliation(s)
- JD Kokales
- Center for Superconductivity Research, Department of Physics, University of Maryland, College Park, Maryland 20742-4111, USA
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Tsuei CC, Kirtley JR. Phase-sensitive evidence for d-wave pairing symmetry in electron-doped cuprate superconductors. PHYSICAL REVIEW LETTERS 2000; 85:182-185. [PMID: 10991189 DOI: 10.1103/physrevlett.85.182] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2000] [Indexed: 05/23/2023]
Abstract
We present phase-sensitive evidence that the electron-doped cuprates Nd(1.85)Ce(0.15)CuO(4-y) (NCCO) and Pr(1.85)Ce(0.15)CuO(4-y) (PCCO) have d-wave pairing symmetry. This evidence was obtained by observing the half-flux quantum effect, using a scanning SQUID microscope, in c-axis-oriented films of NCCO or PCCO epitaxially grown on tricrystal [100] SrTiO3 substrates designed to be frustrated for a d(x(2)-y(2)) order parameter. Samples with two other configurations, designed to be unfrustrated for a d-wave superconductor, do not show the half-flux quantum effect.
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Affiliation(s)
- CC Tsuei
- IBM T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, New York 10598, USA
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