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Crystal Growth by the Floating Zone Method of Ce-Substituted Crystals of the Topological Kondo Insulator SmB6. CRYSTALS 2020. [DOI: 10.3390/cryst10090827] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
SmB6 is a mixed valence topological Kondo insulator. To investigate the effect of substituting Sm with magnetic Ce ions on the physical properties of samarium hexaboride, Ce-substituted SmB6 crystals were grown by the floating zone method for the first time as large, good quality single crystal boules. The crystal growth conditions are reported. Structural, magnetic and transport properties of single crystals of Sm1−xCexB6 (x=0.05, 0.10 and 0.20) were investigated using X-ray diffraction techniques, electrical resistivity and magnetisation measurements. Phase composition analysis of the powder X-ray diffraction data collected on the as-grown boules revealed that the main phase was that of the parent compound, SmB6. Substitution of Sm ions with magnetic Ce ions does not lead to long-range magnetic ordering in the Sm1−xCexB6 crystals. The substitution with 5% Ce and above suppresses the cross-over from bulk conductivity at high temperatures to surface-only conductivity at low temperatures.
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2
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Zhuang JT, Zheng XJ, Wang ZY, Ming X, Li H, Liu Y, Song HF. Valence transition in topological Kondo insulator. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:035602. [PMID: 31536975 DOI: 10.1088/1361-648x/ab4625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We investigate the valence transition in three-dimensional topological Kondo insulator through slave-boson analysis of periodic Anderson model. By including the effect of intra-atomic Coulomb correlation [Formula: see text] between conduction and local electrons, we find a first-order valence transition from Kondo region to mixed valence state upon ascending of local f- level above a critical [Formula: see text], and this valence transition usually occurs very close to or simultaneously with a topological transition. Near the parameter region of zero-temperature valence transition, rise of temperature can generate a thermal valence transition from mixed valence to Kondo region, accompanied by a first-order topological transition. Remarkably, above a critical [Formula: see text] which is considerably smaller than that generating paramagnetic valence transition, the original continuous antiferromagnetic transition is shifted to first order one, at which a discontinuous valence shift takes place. Upon increasing [Formula: see text], the paramagnetic valence transition approaches then converges with the first-order antiferromagnetic transition, leaving a significant valence shift on the magnetic boundary. The continuous antiferromagnetic transition, first-order antiferromagnetic transition, paramagnetic valence transition and topological transitions are all summarized in a global phase diagram. Our proposed exotic transition processes can help to understand the thermal valence variation as well as the valence shift around the pressure-induced magnetic transition in topological Kondo insulator candidates and in other heavy-fermion systems.
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Affiliation(s)
- Jia-Tao Zhuang
- College of Science, Guilin University of Technology, Guilin 541004, People's Republic of China
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3
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Kushwaha SK, Chan MK, Park J, Thomas SM, Bauer ED, Thompson JD, Ronning F, Rosa PFS, Harrison N. Magnetic field-tuned Fermi liquid in a Kondo insulator. Nat Commun 2019; 10:5487. [PMID: 31792205 PMCID: PMC6889157 DOI: 10.1038/s41467-019-13421-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2019] [Accepted: 11/02/2019] [Indexed: 11/08/2022] Open
Abstract
Kondo insulators are expected to transform into metals under a sufficiently strong magnetic field. The closure of the insulating gap stems from the coupling of a magnetic field to the electron spin, yet the required strength of the magnetic field-typically of order 100 T-means that very little is known about this insulator-metal transition. Here we show that Ce[Formula: see text]Bi[Formula: see text]Pd[Formula: see text], owing to its fortuitously small gap, provides an ideal Kondo insulator for this investigation. A metallic Fermi liquid state is established above a critical magnetic field of only [Formula: see text] 11 T. A peak in the strength of electronic correlations near [Formula: see text], which is evident in transport and susceptibility measurements, suggests that Ce[Formula: see text]Bi[Formula: see text]Pd[Formula: see text] may exhibit quantum criticality analogous to that reported in Kondo insulators under pressure. Metamagnetism and the breakdown of the Kondo coupling are also discussed.
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Affiliation(s)
- Satya K Kushwaha
- MPA-MAGLAB, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Mun K Chan
- MPA-MAGLAB, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Joonbum Park
- MPA-MAGLAB, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - S M Thomas
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Eric D Bauer
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - J D Thompson
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - F Ronning
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Priscila F S Rosa
- MPA-CMMS, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA
| | - Neil Harrison
- MPA-MAGLAB, Los Alamos National Laboratory, Los Alamos, NM, 87545, USA.
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4
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Li H, Zhong Y, Liu Y, Luo HG, Song HF. [Formula: see text] classification for a novel antiferromagnetic topological insulating phase in three-dimensional topological Kondo insulator. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:435601. [PMID: 30215616 DOI: 10.1088/1361-648x/aae17b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Antiferromagnetic topological insulator (AFTI) is a topological matter that breaks time-reversal symmetry. Since its proposal, explorations of AFTI in strong-correlated systems are still lacking. In this paper, we show for the first time that a novel AFTI phase can be realized in three-dimensional topological Kondo insulator (TKI). In a wide parameter region, the ground states of TKI undergo a second-order transition to antiferromagnetic insulating phases which conserve a combined symmetry of time reversal and a lattice translation, allowing us to derive a [Formula: see text]-classification formula for these states. By calculating the [Formula: see text] index, the antiferromagnetic insulating states are classified into AFTI or non-topological antiferromagnetic insulator (nAFI) in different parameter regions. On the antiferromagnetic surfaces in AFTI, we find topologically protected gapless Dirac cones inside the bulk gap, leading to metallic Fermi rings exhibiting helical spin texture with weak spin-momentum locking. Depending on model parameters, the magnetic transitions take place either between AFTI and strong topological insulator, or between nAFI and weak topological insulator. By varying some model parameters, we find a topological transition between AFTI and nAFI, driving by closing of bulk gap. Our work may account for the pressure-induced magnetism in TKI compound SmB6, and helps to explore richer AFTI phases in heavy-fermion systems as well as in other strong-correlated systems.
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Affiliation(s)
- Huan Li
- College of Science, Guilin University of Technology, Guilin 541004, People's Republic of China
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5
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Tomczak JM. Thermoelectricity in correlated narrow-gap semiconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:183001. [PMID: 29633717 DOI: 10.1088/1361-648x/aab284] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
We review many-body effects, their microscopic origin, as well as their impact on thermoelectricity in correlated narrow-gap semiconductors. Members of this class-such as FeSi and FeSb2-display an unusual temperature dependence in various observables: insulating with large thermopowers at low temperatures, they turn bad metals at temperatures much smaller than the size of their gaps. This insulator-to-metal crossover is accompanied by spectral weight-transfers over large energies in the optical conductivity and by a gradual transition from activated to Curie-Weiss-like behaviour in the magnetic susceptibility. We show a retrospective of the understanding of these phenomena, discuss the relation to heavy-fermion Kondo insulators-such as Ce3Bi4Pt3 for which we present new results-and propose a general classification of paramagnetic insulators. From the latter, FeSi emerges as an orbital-selective Kondo insulator. Focussing on intermetallics such as silicides, antimonides, skutterudites, and Heusler compounds we showcase successes and challenges for the realistic simulation of transport properties in the presence of electronic correlations. Further, we explore new avenues in which electronic correlations may contribute to the improvement of thermoelectric performance.
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Affiliation(s)
- Jan M Tomczak
- Institute of Solid State Physics, TU Wien, A-1040 Vienna, Austria
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6
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Zhou Y, Wu Q, Rosa PFS, Yu R, Guo J, Yi W, Zhang S, Wang Z, Wang H, Cai S, Yang K, Li A, Jiang Z, Zhang S, Wei X, Huang Y, Sun P, Yang YF, Fisk Z, Si Q, Zhao Z, Sun L. Quantum phase transition and destruction of Kondo effect in pressurized SmB 6. Sci Bull (Beijing) 2017; 62:1439-1444. [PMID: 36659393 DOI: 10.1016/j.scib.2017.10.008] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Revised: 10/16/2017] [Accepted: 10/16/2017] [Indexed: 01/21/2023]
Abstract
SmB6 has been a well-known Kondo insulator for decades, but recently attracts extensive new attention as a candidate topological system. Studying SmB6 under pressure provides an opportunity to acquire the much-needed understanding about the effect of electron correlations on both the metallic surface state and bulk insulating state. Here we do so by studying the evolution of two transport gaps (low temperature gap El and high temperature gap Eh) associated with the Kondo effect by measuring the electrical resistivity under high pressure and low temperature (0.3 K) conditions. We associate the gaps with the bulk Kondo hybridization, and from their evolution with pressure we demonstrate an insulator-to-metal transition at ∼4 GPa. At the transition pressure, a large change in the Hall number and a divergence tendency of the electron-electron scattering coefficient provide evidence for a destruction of the Kondo entanglement in the ground state. Our results raise the new prospect for studying topological electronic states in quantum critical materials settings.
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Affiliation(s)
- Yazhou Zhou
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Qi Wu
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Priscila F S Rosa
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA; Los Alamos National Laboratory, Los Alamos, NM 87545, USA
| | - Rong Yu
- Department of Physics, Renmin University of China, Beijing 100872, China; Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China; Collaborative Innovation Center of Advanced Microstructures, Nanjing 210093, China
| | - Jing Guo
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Wei Yi
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shan Zhang
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Zhe Wang
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Honghong Wang
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Shu Cai
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Ke Yang
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Aiguo Li
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Zheng Jiang
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Shuo Zhang
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Xiangjun Wei
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Yuying Huang
- Shanghai Synchrotron Radiation Facilities, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
| | - Peijie Sun
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Yi-Feng Yang
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China; Collaborative Innovation Center of Quantum Matter, Beijing 100190, China
| | - Zachary Fisk
- Department of Physics and Astronomy, University of California, Irvine, CA 92697, USA
| | - Qimiao Si
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China; Department of Physics & Astronomy, Rice University, Houston, TX 77005, USA
| | - Zhongxian Zhao
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China; Collaborative Innovation Center of Quantum Matter, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100190, China
| | - Liling Sun
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, China; Collaborative Innovation Center of Quantum Matter, Beijing 100190, China; University of Chinese Academy of Sciences, Beijing 100190, China.
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7
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Ramos E, Franco R, Silva-Valencia J, Foglio ME, Figueira MS. The role of short-range magnetic correlations in the gap opening of topological Kondo insulators. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:345601. [PMID: 28607220 DOI: 10.1088/1361-648x/aa791b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In this article we investigate the effects of short-range anti-ferromagnetic correlations on the gap opening of topological Kondo insulators. We add a Heisenberg term to the periodic Anderson model at the limit of strong correlations in order to allow a small degree of hopping of the localized electrons between neighboring sites of the lattice. This new model is adequate for studying topological Kondo insulators, whose paradigmatic material is the compound [Formula: see text]. The main finding of the article is that the short-range antiferromagnetic correlations, present in some Kondo insulators, contribute decisively to the opening of the Kondo gap in their density of states. These correlations are produced by the interaction between moments on the neighboring sites of the lattice. For simplicity, we solve the problem on a two dimensional square lattice. The starting point of the model is the [Formula: see text] ions orbitals, with [Formula: see text] multiplet in the presence of spin-orbit coupling. We present results for the Kondo and for the antiferromagnetic correlation functions. We calculate the phase diagram of the model, and as we vary the [Formula: see text] level position from the empty regime to the Kondo regime, the system develops metallic and topological Kondo insulator phases. The band structure calculated shows that the model describes a strong topological insulator.
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Affiliation(s)
- E Ramos
- Departamento de Física, Universidad Nacional de Colombia, A. A. 5997, Bogotá, Colombia
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8
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Sun L, Wu Q. Pressure-induced exotic states in rare earth hexaborides. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2016; 79:084503. [PMID: 27376406 DOI: 10.1088/0034-4885/79/8/084503] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Finding the exotic phenomena in strongly correlated electron systems (SCESs) and understanding the corresponding microphysics have long been the research frontiers of condensed matter physics. The remarkable examples for the intriguing phenomena discovered in past years include unconventional superconductivity, heavy Fermion behaviors, giant magneto-resistance and so on. A fascinating type of rare earth hexaboride RB6 (R = Sm, Yb, Eu and Ce) belongs to a strongly correlated electron system (SCES), but shows unusual ambient-pressure and high-pressure behaviors beyond the phenomena mentioned above. Particularly, the recent discovery of the coexistence of an unusual metallic surface state and an insulating bulk state in SmB6, known to be a Kondo insulator decades ago, by theoretical calculations and many experimental measurements creates new interest for the investigation of the RB6. This significant progress encourages people to revisit the RB6 with an attempt to establish a new physics that links the SCES and the unusual metallic surface state which is a common feature of a topological insulator (TI). It is well known that pressure has the capability of tuning the electronic structure and modifying the ground state of solids, or even inducing a quantum phase transition which is one of the kernel issues in studies of SCESs. In this brief review, we will describe the progress in high pressure studies on the RB6 based on our knowledge and research interests, mainly focusing on the pressure-induced phenomena in YbB6 and SmB6, especially on the quantum phase transitions and their connections with the valence state of the rare earth ions. Moreover, some related high-pressure results obtained from CeB6 and EuB6 are also included. Finally, a summary is given in the conclusions and perspectives section.
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Affiliation(s)
- Liling Sun
- Institute of Physics and Beijing National Laboratory for Condensed Matter Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China. Collaborative Innovation Center of Quantum Matter, Beijing 100190, People's Republic of China
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9
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Butch NP, Paglione J, Chow P, Xiao Y, Marianetti CA, Booth CH, Jeffries JR. Pressure-Resistant Intermediate Valence in the Kondo Insulator SmB_{6}. PHYSICAL REVIEW LETTERS 2016; 116:156401. [PMID: 27127976 DOI: 10.1103/physrevlett.116.156401] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Indexed: 06/05/2023]
Abstract
Resonant x-ray emission spectroscopy was used to determine the pressure dependence of the f-electron occupancy in the Kondo insulator SmB_{6}. Applied pressure reduces the f occupancy, but surprisingly, the material maintains a significant divalent character up to a pressure of at least 35 GPa. Thus, the closure of the resistive activation energy gap and onset of magnetic order are not driven by stabilization of an integer valent state. Over the entire pressure range, the material maintains a remarkably stable intermediate valence that can in principle support a nontrivial band structure.
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Affiliation(s)
- Nicholas P Butch
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
- NIST Center for Neutron Research, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, Maryland 20899, USA
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
| | - Johnpierre Paglione
- Center for Nanophysics and Advanced Materials, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
| | - Paul Chow
- HP-CAT, Geophysical Laboratory, Carnegie Institute of Washington, Argonne, Illinois 60439, USA
| | - Yuming Xiao
- HP-CAT, Geophysical Laboratory, Carnegie Institute of Washington, Argonne, Illinois 60439, USA
| | - Chris A Marianetti
- Department of Applied Physics and Applied Mathematics, Columbia University, New York, New York 10027, USA
| | - Corwin H Booth
- Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | - Jason R Jeffries
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550, USA
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10
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Tan BS, Hsu YT, Zeng B, Hatnean MC, Harrison N, Zhu Z, Hartstein M, Kiourlappou M, Srivastava A, Johannes MD, Murphy TP, Park JH, Balicas L, Lonzarich GG, Balakrishnan G, Sebastian SE. Heavy fermions. Unconventional Fermi surface in an insulating state. Science 2015; 349:287-90. [PMID: 26138105 DOI: 10.1126/science.aaa7974] [Citation(s) in RCA: 77] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 06/24/2015] [Indexed: 11/03/2022]
Abstract
Insulators occur in more than one guise; a recent finding was a class of topological insulators, which host a conducting surface juxtaposed with an insulating bulk. Here, we report the observation of an unusual insulating state with an electrically insulating bulk that simultaneously yields bulk quantum oscillations with characteristics of an unconventional Fermi liquid. We present quantum oscillation measurements of magnetic torque in high-purity single crystals of the Kondo insulator SmB6, which reveal quantum oscillation frequencies characteristic of a large three-dimensional conduction electron Fermi surface similar to the metallic rare earth hexaborides such as PrB6 and LaB6. The quantum oscillation amplitude strongly increases at low temperatures, appearing strikingly at variance with conventional metallic behavior.
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Affiliation(s)
- B S Tan
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - Y-T Hsu
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - B Zeng
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | | | - N Harrison
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87504, USA
| | - Z Zhu
- National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, NM 87504, USA
| | - M Hartstein
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - M Kiourlappou
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - A Srivastava
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - M D Johannes
- Center for Computational Materials Science, Naval Research Laboratory, Washington, DC 20375, USA
| | - T P Murphy
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | - J-H Park
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | - L Balicas
- National High Magnetic Field Laboratory, Tallahassee, FL 32310, USA
| | - G G Lonzarich
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK
| | - G Balakrishnan
- Department of Physics, University of Warwick, Coventry CV4 7AL, UK
| | - Suchitra E Sebastian
- Cavendish Laboratory, Cambridge University, JJ Thomson Avenue, Cambridge CB3 OHE, UK.
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11
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Barla A, Wilhelm H, Forthaus MK, Strohm C, Rüffer R, Schmidt M, Koepernik K, Rössler UK, Abd-Elmeguid MM. Pressure-induced inhomogeneous chiral-spin ground state in FeGe. PHYSICAL REVIEW LETTERS 2015; 114:016803. [PMID: 25615493 DOI: 10.1103/physrevlett.114.016803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/15/2013] [Indexed: 06/04/2023]
Abstract
(57)Fe nuclear forward scattering on the chiral magnet FeGe reveals an extremely large precursor phase region above the helimagnetic ordering temperature T(C)(p) and beyond the pressure-induced quantum phase transition at 19 GPa. The decrease of the magnetic hyperfine field ⟨B(hf)⟩ with pressure is accompanied by a large increase of the width of the distribution of ⟨B(hf)⟩, indicating a strong quasistatic inhomogeneity of the magnetic states in the precursor region. Hyperfine fields of the order of 4 T (equivalent to a magnetic moment μ(Fe)≈0.4μ(B)) persist up to 28.5 GPa. No signatures of magnetic order have been found at about 31 GPa. The results, supported by ab initio calculations, suggest that chiral magnetic precursor phenomena, such as an inhomogeneous chiral-spin state, are vastly enlarged due to increasing spin fluctuations as FeGe is tuned to its quantum phase transition.
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Affiliation(s)
- A Barla
- Istituto di Struttura della Materia, ISM-CNR, I-34149 Trieste, Italy and ALBA Synchrotron Light Source, E-08290 Cerdanyola del Vallés, Barcelona, Spain
| | - H Wilhelm
- Diamond Light Source Ltd, Chilton, Didcot, Oxfordshire OX11 0DE, United Kingdom
| | - M K Forthaus
- II. Physikalisches Institut, Universität zu Köln, D-50937 Köln, Germany
| | - C Strohm
- European Synchrotron Radiation Facility, F-38043 Grenoble, France
| | - R Rüffer
- European Synchrotron Radiation Facility, F-38043 Grenoble, France
| | - M Schmidt
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
| | - K Koepernik
- IFW Dresden, Postfach 270116, D-01171 Dresden, Germany
| | - U K Rössler
- IFW Dresden, Postfach 270116, D-01171 Dresden, Germany
| | - M M Abd-Elmeguid
- II. Physikalisches Institut, Universität zu Köln, D-50937 Köln, Germany
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12
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Kim DJ, Thomas S, Grant T, Botimer J, Fisk Z, Xia J. Surface hall effect and nonlocal transport in SmB₆: evidence for surface conduction. Sci Rep 2013; 3:3150. [PMID: 24193196 PMCID: PMC3818682 DOI: 10.1038/srep03150] [Citation(s) in RCA: 238] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Accepted: 10/22/2013] [Indexed: 11/09/2022] Open
Abstract
A topological insulator (TI) is an unusual quantum state in which the insulating bulk is topologically distinct from vacuum, resulting in a unique metallic surface that is robust against time-reversal invariant perturbations. The surface transport, however, remains difficult to isolate from the bulk conduction in most existing TI crystals (particularly Bi₂Se₃, Bi₂Te₃ and Sb₂Te₃) due to impurity caused bulk conduction. We report in large crystals of topological Kondo insulator (TKI) candidate material SmB₆ the thickness-independent surface Hall effects and non-local transport, which persist after various surface perturbations. These results serve as proof that at low temperatures SmB₆ has a metallic surface that surrounds an insulating bulk, paving the way for transport studies of the surface state in this proposed TKI material.
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Affiliation(s)
- D. J. Kim
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
- These authors contributed equally to this work
| | - S. Thomas
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
- These authors contributed equally to this work
| | - T. Grant
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - J. Botimer
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Z. Fisk
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
| | - Jing Xia
- Dept. of Physics and Astronomy, University of California, Irvine, California 92697, USA
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13
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Large, high quality single-crystals of the new Topological Kondo Insulator, SmB6. Sci Rep 2013; 3:3071. [PMID: 24166216 PMCID: PMC3810659 DOI: 10.1038/srep03071] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2013] [Accepted: 10/11/2013] [Indexed: 11/17/2022] Open
Abstract
SmB6 has recently been predicted to be a Topological Kondo Insulator, the first strongly correlated heavy fermion material to exhibit topological surface states. High quality crystals are necessary to investigate the topological properties of this material. Single crystal growth of the rare earth hexaboride, SmB6, has been carried out by the floating zone technique using a high power xenon arc lamp image furnace. Large, high quality single-crystals are obtained by this technique. The crystals produced by the floating zone technique are free of contamination from flux materials and have been characterised by resistivity and magnetisation measurements. These crystals are ideally suited for the investigation of both the surface and bulk properties of SmB6.
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14
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Feng XY, Dai J, Chung CH, Si Q. Competing topological and Kondo insulator phases on a honeycomb lattice. PHYSICAL REVIEW LETTERS 2013; 111:016402. [PMID: 23863017 DOI: 10.1103/physrevlett.111.016402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Revised: 03/18/2013] [Indexed: 06/02/2023]
Abstract
We investigate the competition between the spin-orbit interaction of itinerant electrons and their Kondo coupling with local moments densely distributed on the honeycomb lattice. We find that the model at half-filling displays a quantum phase transition between topological and Kondo insulators at a nonzero Kondo coupling. In the Kondo-screened case, tuning the electron concentration can lead to a new topological insulator phase. The results suggest that the heavy-fermion phase diagram contains a new regime with a competition among topological, Kondo-coherent and magnetic states, and that the regime may be especially relevant to Kondo lattice systems with 5d-conduction electrons. Finally, we discuss the implications of our results in the context of the recent experiments on SmB(6) implicating the surface states of a topological insulator, as well as the existing experiments on the phase transitions in SmB(6) under pressure and in CeNiSn under chemical pressure.
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Affiliation(s)
- Xiao-Yong Feng
- Condensed Matter Group, Department of Physics, Hangzhou Normal University, Hangzhou 310036, China
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Danzenbächer S, Vyalikh DV, Kucherenko Y, Kade A, Laubschat C, Caroca-Canales N, Krellner C, Geibel C, Fedorov AV, Dessau DS, Follath R, Eberhardt W, Molodtsov SL. Hybridization phenomena in nearly-half-filled f-shell electron systems: photoemission study of EuNi2P2. PHYSICAL REVIEW LETTERS 2009; 102:026403. [PMID: 19257299 DOI: 10.1103/physrevlett.102.026403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2008] [Indexed: 05/27/2023]
Abstract
The mixed-valent compound EuNi2P2 was studied by photoemission. Observed splittings and dispersions of the Eu 4f;{6} final state close to energy crossings of the Eu 4f and Ni 3d states are explained in terms of hybridization by a momentum and energy dependence of the electron hopping matrix element. These data obtained for a system with more than one 4f electron (hole) show that dispersions and hybridization gaps related to Kondo and heavy-fermion behavior can be found in other rare-earth-metal compounds apart from Ce and Yb-based ones.
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Affiliation(s)
- S Danzenbächer
- Institut für Festkörperphysik, Technische Universität Dresden, D-01062 Dresden, Germany
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Derr J, Knebel G, Lapertot G, Salce B, Méasson MA, Flouquet J. Valence and magnetic ordering in intermediate valence compounds: TmSe versus SmB(6). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:2089-2106. [PMID: 21697577 DOI: 10.1088/0953-8984/18/6/021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The intermediate valence systems TmSe and SmB(6) have been investigated up to 16 and 18 GPa by ac microcalorimetry with a pressure (p) tuning realized in situ at low temperature. For TmSe, the transition from an antiferromagnetic insulator for p<3 GPa to an antiferromagnetic metal at higher pressure has been confirmed. A drastic change in the p variation of the Néel temperature (T(N)) is observed at 3 GPa. In the metallic phase (p>3 GPa), T(N) is found to increase linearly with p. A similar linear p increase of T(N) is observed for the quasitrivalent compound TmS, which is at ambient pressure equivalent to TmSe at p∼7 GPa. In the case of SmB(6) long range magnetism has been detected above p∼8 GPa, i.e. at a pressure slightly higher than the pressure of the insulator to metal transition. However a homogeneous magnetic phase occurs only above 10 GPa. The magnetic and electronic properties are related to the renormalization of the 4f wavefunction either to the divalent or the trivalent configurations. As observed in SmS, long range magnetism in SmB(6) occurs already far below the pressure where a trivalent Sm(3+) state will be reached. It seems possible to describe roughly the physical properties of the intermediate valence equilibrium by assuming formulae for the Kondo lattice temperature depending on the valence configuration. Comparison is also made with the appearance of long range magnetism in cerium and ytterbium heavy fermion compounds.
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Affiliation(s)
- J Derr
- Département de Recherche Fondamentale sur la Matière Condensée, CEA Grenoble, 17 rue des Martyrs, 38054 Grenoble Cedex 9, France
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