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Wu L, Si J, Guan S, Zhang H, Dou J, Luo J, Yang J, Yu H, Zhang J, Ma X, Yang P, Zhou R, Liu M, Hong F, Yu X. Record-High T_{c} and Dome-Shaped Superconductivity in a Medium-Entropy Alloy TaNbHfZr under Pressure up to 160 GPa. Phys Rev Lett 2024; 132:166002. [PMID: 38701470 DOI: 10.1103/physrevlett.132.166002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 03/06/2024] [Accepted: 03/25/2024] [Indexed: 05/05/2024]
Abstract
Superconductivity has been one of the focal points in medium and high-entropy alloys (MEAs-HEAs) since the discovery of the body-centered cubic (bcc) HEA superconductor in 2014. Until now, the superconducting transition temperature (T_{c}) of most MEA and HEA superconductors has not exceeded 10 K. Here, we report a TaNbHfZr bulk MEA superconductor crystallized in the BCC structure with a T_{c} of 15.3 K which set a new record. During compression, T_{c} follows a dome-shaped curve. It reaches a broad maximum of roughly 15 K at around 70 GPa before decreasing to 9.3 K at 157.2 GPa. First-principles calculations attribute the dome-shaped curve to two competing effects, that is, the enhancement of the logarithmically averaged characteristic phonon frequency ω_{log} and the simultaneous suppression of the electron-phonon coupling constant λ. Thus, TaNbHfZr MEA may have a promising future for studying the underlying quantum physics, as well as developing new applications under extreme conditions.
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Affiliation(s)
- Liyunxiao Wu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jianguo Si
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Shixue Guan
- School of Applied Science, Beijing Information Science and Technology University, Beijing 100192, China
| | - He Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jie Dou
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jun Luo
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Jie Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Hui Yu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Jiawei Zhang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Xiaoli Ma
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
| | - Pengtao Yang
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
| | - Rui Zhou
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Miao Liu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
- Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Fang Hong
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
| | - Xiaohui Yu
- Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
- School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
- Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, China
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2
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Beck N, Gomez Martinez D, Albrecht-Schönzart TE. Pressure-Induced Coordination Number Transition in Lanthanide Mellitate Coordination Polymers: Structure and Spectroscopy. Inorg Chem 2023; 62:15375-15381. [PMID: 37700461 DOI: 10.1021/acs.inorgchem.3c00933] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/14/2023]
Abstract
High external pressure is found to induce a non-coordinated water molecule to bond to cerium in a previously studied mellitate coordination polymer, as determined by high-pressure single-crystal X-ray diffraction, resulting in a coordination number transition at 3.85 GPa from 9 to 9.5 where half the cerium ions are 10-coordinate. Also, bond length changes due to increased pressure are experimentally measured, whereas the cerium-carboxylate bond lengths overall change by -0.004(9) Å/GPa, the cerium-water bonds by -0.016(3) Å/GPa, and cerium-oxygen bonds overall by -0.010(6) Å/GPa, which corresponds well with theoretical bond length decreases determined for similar compounds. The high-pressure absorbance spectra of the analogous neodymium mellitate are examined and compared with the structural changes observed.
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Affiliation(s)
- Nicholas Beck
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Daniela Gomez Martinez
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306, United States
| | - Thomas E Albrecht-Schönzart
- Department of Chemistry and Nuclear Science and Engineering Center, Colorado School of Mines, Golden, Colorado 80401, United States
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Shen X, Ma H, Bhoi D, Gouchi J, Uwatoko Y, Dalan A, Kawamura Y, Sato H, Umehara I, Uehara M. Pressure Induced Superconductivity and Multiple Structural Transitions in CsCl-Type Cubic CeZn Single Crystal. Crystals 2022; 12:571. [DOI: 10.3390/cryst12050571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
CsCl-type cubic compound CeZn exhibits a paramagnetic (PM) to antiferromagnetic (AFM) first-order transition at TN ~ 30 K accompanied by a simultaneous structural transition from cubic to tetragonal structure as temperature decreases. Applying the pressure, the coupled magnetic and crystal structural transition becomes separated above 1.0 GPa and then the AFM order changes to ferromagnetic (FM). The FM ordering temperature decreases with further applying pressure and changes to a nonmagnetic state above ~3.0 GPa. In the nonmagnetic state, we discovered superconductivity below Tsc ~ 1.3 K over 5.5 GPa, which survives even up to 9.5 GPa. Investigation of single crystal X-ray diffraction at room temperature reveals that CeZn undergoes a sequential crystal structural change with increasing pressure from cubic at ambient pressure to the monoclinic structure at 8.2 GPa via tetragonal and orthorhombic structure. The detailed analysis of crystal structure in CeZn single crystal evidenced that the emergence of superconductivity is related to the orthorhombic-to-monoclinic transition implying a nonmagnetic origin of the Cooper pair formation.
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Kuga K, Matsumoto Y, Okawa M, Suzuki S, Tomita T, Sone K, Shimura Y, Sakakibara T, Nishio-Hamane D, Karaki Y, Takata Y, Matsunami M, Eguchi R, Taguchi M, Chainani A, Shin S, Tamasaku K, Nishino Y, Yabashi M, Ishikawa T, Nakatsuji S. Quantum valence criticality in a correlated metal. Sci Adv 2018; 4:eaao3547. [PMID: 29492456 PMCID: PMC5825215 DOI: 10.1126/sciadv.aao3547] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Accepted: 01/19/2018] [Indexed: 06/08/2023]
Abstract
A valence critical end point existing near the absolute zero provides a unique case for the study of a quantum version of the strong density fluctuation at the Widom line in the supercritical fluids. Although singular charge and orbital dynamics are suggested theoretically to alter the electronic structure significantly, breaking down the standard quasi-particle picture, this has never been confirmed experimentally to date. We provide the first empirical evidence that the proximity to quantum valence criticality leads to a clear breakdown of Fermi liquid behavior. Our detailed study of the mixed valence compound α-YbAlB4 reveals that a small chemical substitution induces a sharp valence crossover, accompanied by a pronounced non-Fermi liquid behavior characterized by a divergent effective mass and unusual T/B scaling in the magnetization.
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Affiliation(s)
- Kentaro Kuga
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | - Yosuke Matsumoto
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Mario Okawa
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Shintaro Suzuki
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Takahiro Tomita
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Keita Sone
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Yasuyuki Shimura
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | - Toshiro Sakakibara
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
| | | | - Yoshitomo Karaki
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- Faculty of Education, University of the Ryukyus, Nishihara, Okinawa 903-0213, Japan
| | | | - Masaharu Matsunami
- Ultraviolet Synchrotron Orbital Radiation Facility, Institute for Molecular Science and The Graduate University for Advanced Studies, Okazaki 444-8585, Japan
| | - Ritsuko Eguchi
- Research Laboratory for Surface Science, Okayama University, Okayama 700-8530, Japan
| | | | - Ashish Chainani
- RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - Shik Shin
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
| | | | - Yoshinori Nishino
- RIKEN SPring-8 Center, Sayo-gun, Hyogo 679-5148, Japan
- Research Institute for Electronic Science, Hokkaido University, Sapporo 001-0021, Japan
| | | | | | - Satoru Nakatsuji
- Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581, Japan
- Core Research for Evolutionary Science and Technology, Japan Science and Technology Agency, Chiyoda, Tokyo 102-0076, Japan
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5
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Brubaker ZE, Stillwell RL, Chow P, Xiao Y, Kenney-Benson C, Ferry R, Jenei Z, Zieve RJ, Jeffries JR. Pressure dependence of Ce valence in CeRhIn 5. J Phys Condens Matter 2018; 30:035601. [PMID: 29239302 DOI: 10.1088/1361-648x/aa9e2b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We have studied the Ce valence as a function of pressure in CeRhIn5 at 300 K and at 22 K using x-ray absorption spectroscopy in partial fluorescent yield mode. At room temperature, we found no detectable change in Ce valence greater than 0.01 up to a pressure of 5.5 GPa. At 22 K, the valence remains robust against pressure below 6 GPa, in contrast to the predicted valence crossover at P = 2.35 GPa. This work yields an upper limit for the change in Ce-valence and suggests that the critical valence fluctuation scenario, in its current form, is unlikely.
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Affiliation(s)
- Z E Brubaker
- Physics Department, University of California, Davis, CA, United States of America. Materials Science Division, Lawrence Livermore National Laboratory, Livermore, CA 94550, United States of America
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6
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Joseph B, Torchio R, Benndorf C, Irifune T, Shinmei T, Pöttgen R, Zerr A. Experimental evidence of an electronic transition in CeP under pressure using Ce L 3 XAS. Phys Chem Chem Phys 2017; 19:17526-17530. [PMID: 28657083 DOI: 10.1039/c7cp03022c] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cerium phosphide undergoes a unit-cell volume discontinuity without any structural phase transitions upon application of a high pressure of ∼10 GPa. This phenomenon is attributed to a change in the electronic charge distribution of the cerium in CeP, but to date no direct experimental verification for this hypothesis has been presented. Here, we report a Ce L3-edge X-ray absorption spectroscopy study under pressure, which provides direct compelling evidence of an electronic transition associated with the above-mentioned isostructural volume discontinuity. The present results should be relevant to the understanding of the phenomenon of pressure induced isostructural transitions involving unit-cell volume collapse.
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Affiliation(s)
- B Joseph
- Elettra-Sincrotrone Trieste, Strada Statale 14, Km 163,5, Basovizza, Trieste, Italy.
| | - R Torchio
- European Synchrotron Radiation Facility, BP220, 38043 Grenoble Cedex, France
| | - C Benndorf
- Institut für Anorganische und Analytische Chemie Universitat Münster, Corrensstrasse 30, 48149, Münster, Germany
| | - T Irifune
- Geodynamics Research Center, Ehime University, Bunkyo-cho, 7908577, Matsuyama, Japan
| | - T Shinmei
- Geodynamics Research Center, Ehime University, Bunkyo-cho, 7908577, Matsuyama, Japan
| | - R Pöttgen
- Institut für Anorganische und Analytische Chemie Universitat Münster, Corrensstrasse 30, 48149, Münster, Germany
| | - A Zerr
- Laboratoire des Sciences des Procédés et des Materiaux LSPM-CNRS, Université Paris 13, Sorbonne Paris Cité 93430, Villetaneuse, France
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7
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Cheng J, Zhai H, Wang Y, Xu W, Liu S, Cao G. Role of valence changes and nanoscale atomic displacements in BiS 2-based superconductors. Sci Rep 2016; 6:37394. [PMID: 27874040 DOI: 10.1038/srep37394] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 10/27/2016] [Indexed: 11/09/2022] Open
Abstract
Superconductivity within layered crystal structures has attracted sustained interest among condensed matter community, primarily due to their exotic superconducting properties. EuBiS2F is a newly discovered member in the BiS2-based superconducting family, which shows superconductivity at 0.3 K without extrinsic doping. With 50 at.% Ce substitution for Eu, superconductivity is enhanced with Tc increased up to 2.2 K. However, the mechanisms for the Tc enhancement have not yet been elucidated. In this study, the Ce-doping effect on the self-electron-doped superconductor EuBiS2F was investigated by X-ray absorption spectroscopy (XAS). We have established a relationship between Ce-doping and the Tc enhancement in terms of Eu valence changes and nanoscale atomic displacements. The new finding sheds light on the interplay among superconductivity, charge and local structure in BiS2-based superconductors.
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8
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Weng ZF, Smidman M, Jiao L, Lu X, Yuan HQ. Multiple quantum phase transitions and superconductivity in Ce-based heavy fermions. Rep Prog Phys 2016; 79:094503. [PMID: 27533524 DOI: 10.1088/0034-4885/79/9/094503] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Heavy fermions have served as prototype examples of strongly-correlated electron systems. The occurrence of unconventional superconductivity in close proximity to the electronic instabilities associated with various degrees of freedom points to an intricate relationship between superconductivity and other electronic states, which is unique but also shares some common features with high temperature superconductivity. The magnetic order in heavy fermion compounds can be continuously suppressed by tuning external parameters to a quantum critical point, and the role of quantum criticality in determining the properties of heavy fermion systems is an important unresolved issue. Here we review the recent progress of studies on Ce based heavy fermion superconductors, with an emphasis on the superconductivity emerging on the edge of magnetic and charge instabilities as well as the quantum phase transitions which occur by tuning different parameters, such as pressure, magnetic field and doping. We discuss systems where multiple quantum critical points occur and whether they can be classified in a unified manner, in particular in terms of the evolution of the Fermi surface topology.
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Affiliation(s)
- Z F Weng
- Center for Correlated Matter and Department of Physics, Zhejiang University, Hangzhou 310058, People's Republic of China
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9
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Abstract
The physical properties of the series CePd3Be(x) (0 ≤ x ≤ 0.47) have been studied. Introducing Be into CePd3 results in a drastic reduction of the Seebeck coefficient from 100 μV K(-1) at 300 K to -2 μV K(-1), respectively. Paramagnetism of Ce(3+) free ions and metallic conduction dominate the physical properties. A structural transition at x = 0.25 is accompanied by a significant lowering of the Kondo temperature and leads to a successive suppression of the thermoelectric performance of CePd3Be(x) with increasing x.
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Affiliation(s)
- Roman Gumeniuk
- Institut für Experimentelle Physik, TU Bergakademie Freiberg, Leipziger Straße 23, 09596 Freiberg, Germany. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer Straße 40, 01187 Dresden, Germany
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10
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Sundermann M, Strigari F, Willers T, Winkler H, Prokofiev A, Ablett JM, Rueff JP, Schmitz D, Weschke E, Sala MM, Al-Zein A, Tanaka A, Haverkort MW, Kasinathan D, Tjeng LH, Paschen S, Severing A. CeRu4Sn6: a strongly correlated material with nontrivial topology. Sci Rep 2015; 5:17937. [PMID: 26658647 DOI: 10.1038/srep17937] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 11/09/2015] [Indexed: 11/08/2022] Open
Abstract
Topological insulators form a novel state of matter that provides new opportunities to create unique quantum phenomena. While the materials used so far are based on semiconductors, recent theoretical studies predict that also strongly correlated systems can show non-trivial topological properties, thereby allowing even the emergence of surface phenomena that are not possible with topological band insulators. From a practical point of view, it is also expected that strong correlations will reduce the disturbing impact of defects or impurities, and at the same increase the Fermi velocities of the topological surface states. The challenge is now to discover such correlated materials. Here, using advanced x-ray spectroscopies in combination with band structure calculations, we infer that CeRu4Sn6 is a strongly correlated material with non-trivial topology.
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11
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Ikeda H, Suzuki MT, Arita R. Emergent loop-nodal s(±)-wave superconductivity in CeCu(2)Si(2): similarities to the iron-based superconductors. Phys Rev Lett 2015; 114:147003. [PMID: 25910154 DOI: 10.1103/physrevlett.114.147003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Indexed: 06/04/2023]
Abstract
Heavy-fermion superconductors are prime candidates for novel electron-pairing states due to the spin-orbital coupled degrees of freedom and electron correlations. Superconductivity in CeCu_{2}Si_{2} discovered in 1979, which is a prototype of unconventional (non-BCS) superconductors in strongly correlated electron systems, still remains unsolved. Here we provide the first report of superconductivity based on the advanced first-principles theoretical approach. We find that the promising candidate is an s_{±}-wave state with loop-shaped nodes on the Fermi surface, different from the widely expected line-nodal d-wave state. The dominant pairing glue is magnetic but high-rank octupole fluctuations. This system shares the importance of multiorbital degrees of freedom with the iron-based superconductors. Our findings reveal not only the long-standing puzzle in this material, but also urge us to reconsider the pairing states and mechanisms in all heavy-fermion superconductors.
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Affiliation(s)
- Hiroaki Ikeda
- Department of Physics, Ritsumeikan University, Kusatsu 525-8577, Japan
| | - Michi-To Suzuki
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Ryotaro Arita
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
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12
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Yamaoka H, Ikeda Y, Jarrige I, Tsujii N, Zekko Y, Yamamoto Y, Mizuki J, Lin JF, Hiraoka N, Ishii H, Tsuei KD, Kobayashi TC, Honda F, Onuki Y. Role of valence fluctuations in the superconductivity of Ce122 compounds. Phys Rev Lett 2014; 113:086403. [PMID: 25192112 DOI: 10.1103/physrevlett.113.086403] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Indexed: 06/03/2023]
Abstract
Pressure dependence of the Ce valence in CeCu(2)Ge(2) has been measured up to 24 GPa at 300 K and to 17 GPa at 18-20 K using x-ray absorption spectroscopy in the partial fluorescence yield. A smooth increase of the Ce valence with pressure is observed across the two superconducting (SC) regions without any noticeable irregularity. The chemical pressure dependence of the Ce valence was also measured in Ce(Cu(1-x)Ni(x))(2)Si(2) at 20 K. A very weak, monotonic increase of the valence with x was observed, without any significant change in the two SC regions. Within experimental uncertainties, our results show no evidence for the valence transition with an abrupt change in the valence state near the SC II region, challenging the valence-fluctuation mediated superconductivity model in these compounds at high pressure and low temperature.
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Affiliation(s)
- H Yamaoka
- RIKEN SPring-8 Center, Sayo, Hyogo 679-5148, Japan
| | - Y Ikeda
- Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - I Jarrige
- National Synchrotron Light Source II, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - N Tsujii
- Quantum Beam Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan
| | - Y Zekko
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - Y Yamamoto
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - J Mizuki
- Graduate School of Science and Technology, Kwansei Gakuin University, Sanda, Hyogo 669-1337, Japan
| | - J-F Lin
- Department of Geological Sciences, The University of Texas at Austin, Austin, Texas 78712, USA and Center for High Pressure Science and Technology Advanced Research (HPSTAR), Shanghai 201203, China
| | - N Hiraoka
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - H Ishii
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - K-D Tsuei
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
| | - T C Kobayashi
- Department of Physics, Okayama University, Okayama 700-8530, Japan
| | - F Honda
- Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313, Japan
| | - Y Onuki
- Faculty of Science, Ryukyu University, Nakagami, Okinawa 903-0213, Japan
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13
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Pourovskii LV, Hansmann P, Ferrero M, Georges A. Theoretical prediction and spectroscopic fingerprints of an orbital transition in CeCu2Si2. Phys Rev Lett 2014; 112:106407. [PMID: 24679316 DOI: 10.1103/physrevlett.112.106407] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2013] [Indexed: 06/03/2023]
Abstract
We show that the heavy-fermion compound CeCu2Si2 undergoes a transition between two regimes dominated by different crystal-field states. At low pressure P and low temperature T the Ce 4f electron resides in the atomic crystal-field ground state, while at high P or T, the electron occupancy and spectral weight is transferred to an excited crystal-field level that hybridizes more strongly with itinerant states. These findings result from first-principles dynamical-mean-field-theory calculations. We predict experimental signatures of this orbital transition in x-ray spectroscopy. The corresponding fluctuations may be responsible for the second high-pressure superconducting dome observed in this and similar materials.
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Affiliation(s)
- L V Pourovskii
- Centre de Physique Théorique, CNRS, École Polytechnique, 91128 Palaiseau, France and Swedish e-science Research Centre (SeRC), Department of Physics, Chemistry and Biology (IFM), Linköping University, SE-58183 Linköping, Sweden
| | - P Hansmann
- Centre de Physique Théorique, CNRS, École Polytechnique, 91128 Palaiseau, France
| | - M Ferrero
- Centre de Physique Théorique, CNRS, École Polytechnique, 91128 Palaiseau, France
| | - A Georges
- Centre de Physique Théorique, CNRS, École Polytechnique, 91128 Palaiseau, France and Collège de France, 11 place Marcelin Berthelot, 75005 Paris, France and DPMC, Université de Genève, 24 quai Ernest Ansermet, CH-1211 Genève, Switzerland
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14
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Ishimatsu N, Matsumoto K, Maruyama H, Kawamura N, Mizumaki M, Sumiya H, Irifune T. Glitch-free X-ray absorption spectrum under high pressure obtained using nano-polycrystalline diamond anvils. J Synchrotron Radiat 2012; 19:768-72. [PMID: 22898956 PMCID: PMC3621395 DOI: 10.1107/s0909049512026088] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 06/08/2012] [Indexed: 05/31/2023]
Abstract
Nano-polycrystalline diamond (NPD) [Irifune et al. (2003), Nature (London), 421, 599] has been used to obtain a glitch-free X-ray absorption spectrum under high pressure. In the case of conventional single-crystal diamond (SCD) anvils, glitches owing to Bragg diffraction from the anvils are superimposed on X-ray absorption spectra. The glitch has long been a serious problem for high-pressure research activities using X-ray spectroscopy because of the difficulties of its complete removal. It is demonstrated that NPD is one of the best candidate materials to overcome this problem. Here a glitch-free absorption spectrum using the NPD anvils over a wide energy range is shown. The advantage and capability of NPD anvils is discussed by a comparison of the glitch map with that of SCD anvils.
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Affiliation(s)
- Naoki Ishimatsu
- Department of Physics, Graduate School of Science, Hiroshima University, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 739-8526, Japan.
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Pixley JH, Kirchner S, Ingersent K, Si Q. Kondo destruction and valence fluctuations in an Anderson model. Phys Rev Lett 2012; 109:086403. [PMID: 23002763 DOI: 10.1103/physrevlett.109.086403] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2011] [Revised: 06/04/2012] [Indexed: 06/01/2023]
Abstract
Unconventional quantum criticality in heavy-fermion systems has been extensively analyzed in terms of a critical destruction of the Kondo effect. Motivated by a recent demonstration of quantum criticality in a mixed-valent heavy-fermion system, β-YbAlB(4), we study a particle-hole-asymmetric Anderson impurity model with a pseudogapped density of states. We demonstrate Kondo destruction at a mixed-valent quantum critical point, where a collapsing Kondo energy scale is accompanied by a singular charge-fluctuation spectrum. Both spin and charge responses scale with energy over temperature (ω/T) and magnetic field over temperature (H/T). Implications for unconventional quantum criticality in mixed-valence heavy fermions are discussed.
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Affiliation(s)
- J H Pixley
- Department of Physics & Astronomy, Rice University, Houston, Texas 77005, USA
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Abstract
A new universality class of quantum criticality emerging in itinerant electron systems with strong local electron correlations is discussed. The quantum criticality of a Ce- or Yb-valence transition gives us a unified explanation for unconventional criticality commonly observed in heavy fermion metals such as YbRh(2)Si(2), β-YbAlB(4), YbCu(5-x)Al(x), and CeIrIn(5). The key origin is due to the locality of the critical valence fluctuation mode emerging near the quantum critical end point of the first-order valence transition, which is caused by strong electron correlations for f electrons. The wider relevance of this new criticality and important future measurements to uncover its origin are also discussed.
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Affiliation(s)
- Shinji Watanabe
- Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu, Fukuoka 804-8550, Japan
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Kotani A, Kvashnina KO, Glatzel P, Parlebas JC, Schmerber G. Single impurity Anderson model versus density functional theory for describing Ce L3 x-ray absorption spectra of CeFe2: resolution of a recent controversy. Phys Rev Lett 2012; 108:036403. [PMID: 22400765 DOI: 10.1103/physrevlett.108.036403] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2011] [Indexed: 05/31/2023]
Abstract
We resolved a recent controversy on the structure of the Ce L(3) x-ray absorption spectra (XAS) of CeFe(2); i.e., which of the single impurity Anderson model (SIAM) and the first-principles band calculations based on the density-functional theory (DFT) describes more appropriately the Ce 4f states and their contribution to the Ce L(3) XAS? For this purpose, we examined the core-hole effect in Ce L(3) XAS as an application of our new method taking advantage of resonant x-ray emission spectroscopy. Our result clearly shows that the Ce L(3) XAS structure is caused by the mixed valence 4f character revealed by the core-hole potential effect as indicated by SIAM, but denies the possibility that the L(3) XAS structure is caused by the 5d band structure with a very small core-hole effect as predicted by band calculations based on DFT.
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Affiliation(s)
- A Kotani
- Photon Factory, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan
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Pereira MSS, de Oliveira IN, Lyra ML. Crossover from tricritical to critical end point behavior in free-standing smectic films. Phys Rev E Stat Nonlin Soft Matter Phys 2011; 84:061706. [PMID: 22304108 DOI: 10.1103/physreve.84.061706] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Indexed: 05/31/2023]
Abstract
We study the smectic to nematic (SmA-N) phase transition taking place at the center of a free-standing film that exhibits enhanced surface order due to the anchoring promoted by a surrounding gas. The usual McMillan mean-field approach predicts that the SmA-N transition in bulk samples can be continuous or discontinuous (first or second order) depending on the molecular geometry, with a tricritical point separating these two regimes. Here we show that the additional orientational order imposed by the surface anchoring stabilizes the surface-induced smectic and nematic phases, leading to the breakdown of the tricritical point and to the emergence of a critical end point. We report the full phase diagram, which depicts four distinct structures as the film thickness is reduced.
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Affiliation(s)
- Maria S S Pereira
- Instituto de Física, Universidade Federal de Alagoas, 57072-970 Maceió, Alagoas, Brazil
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Gumeniuk R, Kvashnina KO, Schnelle W, Nicklas M, Borrmann H, Rosner H, Skourski Y, Tsirlin AA, Leithe-Jasper A, Grin Y. Physical properties and valence state of cerium in the filled skutterudite CePt₄Ge₁₂. J Phys Condens Matter 2011; 23:465601. [PMID: 22056917 DOI: 10.1088/0953-8984/23/46/465601] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Electronic, magnetic, and transport properties of the filled platinum-germanium skutterudite CePt₄Ge₁₂ are investigated. High resolution x-ray absorption spectroscopy measurements at the cerium L(III) edge demonstrate that CePt₄Ge₁₂ in this compound has a temperature-independent valence close to three. However, magnetic susceptibility, thermopower, Hall effect, and electronic specific heat reveal a broad maximum at Tmax D 65-80 K, suggesting the presence of valence fluctuations. The Sommerfeld coefficient γ = 105 mJ mol⁻¹ K⁻², deduced from specific heat, indicates moderately enhanced band masses for CePt₄Ge₁₂. We discuss these findings and conclude that CePt₄Ge₁₂ represents a system at the border between intermediate valence (IV) and Kondo lattice behavior. In addition, the lattice specific heat and the thermal conductivity are discussed with respect to the vibrational dynamics of Ce in the [Pt₄Ge₁₂] framework.
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Affiliation(s)
- R Gumeniuk
- Max-Planck-Institut für Chemische Physik fester Stoffe, 01187 Dresden, Germany
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