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Wang L, Hu R, Anand Y, Saha SR, Jeffries JR, Paglione J. Pressure-Induced Exciton Formation and Superconductivity in Platinum-Based Mineral Sperrylite. MATERIALS (BASEL, SWITZERLAND) 2024; 17:3476. [PMID: 39063766 PMCID: PMC11277940 DOI: 10.3390/ma17143476] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2024] [Revised: 07/08/2024] [Accepted: 07/11/2024] [Indexed: 07/28/2024]
Abstract
We report a comprehensive study of Sperrylite (PtAs2), the main platinum source in natural minerals, as a function of applied pressures up to 150 GPa. While no structural phase transition is detected from pressure-dependent X-ray measurements, the unit cell volume shrinks monotonically with pressure following the third-order Birch-Murnaghan equation of state. The mildly semiconducting behavior found in pure synthesized crystals at ambient pressures becomes more insulating upon increasing the applied pressure before metalizing at higher pressures, giving way to the appearance of an abrupt decrease in resistance near 3 K at pressures above 92 GPa consistent with the onset of a superconducing phase. The pressure evolution of the calculated electronic band structure reveals the same physical trend as our transport measurements, with a non-monotonic evolution explained by a hole band that is pushed below the Fermi energy and an electron band that approaches it as a function of pressure, both reaching a touching point suggestive of an excitonic state. A Lifshitz transition of the electronic structure and an increase in the density of states may naturally explain the onset of superconductivity in this material.
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Affiliation(s)
- Limin Wang
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Rongwei Hu
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Yash Anand
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Shanta R. Saha
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
| | - Jason R. Jeffries
- Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA
| | - Johnpierre Paglione
- Maryland Quantum Materials Center, Department of Physics, University of Maryland, College Park, MD 20742, USA
- Canadian Institute for Advanced Research, Toronto, ON M5G 1Z8, Canada
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Zhou BT, Pathak V, Franz M. Quantum-Geometric Origin of Out-of-Plane Stacking Ferroelectricity. PHYSICAL REVIEW LETTERS 2024; 132:196801. [PMID: 38804928 DOI: 10.1103/physrevlett.132.196801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2023] [Revised: 11/16/2023] [Accepted: 04/10/2024] [Indexed: 05/29/2024]
Abstract
Stacking ferroelectricity (SFE) has been discovered in a wide range of van der Waals materials and holds promise for applications, including photovoltaics and high-density memory devices. We show that the microscopic origin of out-of-plane stacking ferroelectric polarization can be generally understood as a consequence of a nontrivial Berry phase borne out of an effective Su-Schrieffer-Heeger model description with broken sublattice symmetry, thus elucidating the quantum-geometric origin of polarization in the extremely nonperiodic bilayer limit. Our theory applies to known stacking ferroelectrics such as bilayer transition-metal dichalcogenides in 3R and T_{d} phases, as well as general AB-stacked honeycomb bilayers with staggered sublattice potential. Our explanatory and self-consistent framework based on the quantum-geometric perspective establishes quantitative understanding of out-of-plane SFE materials beyond symmetry principles.
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Affiliation(s)
- Benjamin T Zhou
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Vedangi Pathak
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Marcel Franz
- Department of Physics and Astronomy & Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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Que Y, Chan YH, Jia J, Das A, Tong Z, Chang YT, Cui Z, Kumar A, Singh G, Mukherjee S, Lin H, Weber B. A Gate-Tunable Ambipolar Quantum Phase Transition in a Topological Excitonic Insulator. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2024; 36:e2309356. [PMID: 38010877 DOI: 10.1002/adma.202309356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 10/26/2023] [Indexed: 11/29/2023]
Abstract
Coulomb interactions among electrons and holes in 2D semimetals with overlapping valence and conduction bands can give rise to a correlated insulating ground state via exciton formation and condensation. One candidate material in which such excitonic state uniquely combines with non-trivial band topology are atomic monolayers of tungsten ditelluride (WTe2 ), in which a 2D topological excitonic insulator (2D TEI) forms. However, the detailed mechanism of the 2D bulk gap formation in WTe2 , in particular with regard to the role of Coulomb interactions, has remained a subject of ongoing debate. Here, it shows that WTe2 is susceptible to a gate-tunable quantum phase transition, evident from an abrupt collapse of its 2D bulk energy gap upon ambipolar field-effect doping. Such gate tunability of a 2D TEI, into either n- and p-type semimetals, promises novel handles of control over non-trivial 2D superconductivity with excitonic pairing.
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Affiliation(s)
- Yande Que
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Yang-Hao Chan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106319, Taiwan
- Physics Division, National Center of Theoretical Physics, Taipei, 10617, Taiwan
| | - Junxiang Jia
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Anirban Das
- Department of Physics, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Center for Atomistic Modelling and Materials Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Zhengjue Tong
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Yu-Tzu Chang
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 106319, Taiwan
| | - Zhenhao Cui
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Amit Kumar
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Gagandeep Singh
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
| | - Shantanu Mukherjee
- Department of Physics, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Center for Atomistic Modelling and Materials Design, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
- Quantum Centre for Diamond and Emergent Materials, Indian Institute of Technology Madras, Chennai, Tamil Nadu, 600036, India
| | - Hsin Lin
- Institute of Physics, Academia Sinica, Taipei, 115201, Taiwan
| | - Bent Weber
- School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, 637371, Singapore
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Crépel V, Guerci D, Cano J, Pixley JH, Millis A. Topological Superconductivity in Doped Magnetic Moiré Semiconductors. PHYSICAL REVIEW LETTERS 2023; 131:056001. [PMID: 37595206 DOI: 10.1103/physrevlett.131.056001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Accepted: 07/06/2023] [Indexed: 08/20/2023]
Abstract
We show that topological superconductivity may emerge upon doping of transition metal dichalcogenide heterobilayers above an integer-filling magnetic state of the topmost valence moiré band. The effective attraction between charge carriers is generated by an electric p-wave Feshbach resonance arising from interlayer excitonic physics and has a tunable strength, which may be large. Together with the low moiré carrier densities reachable by gating, this robust attraction enables access to the long-sought p-wave BEC-BCS transition. The topological protection arises from an emergent time reversal symmetry occurring when the magnetic order and long wavelength magnetic fluctuations do not couple different valleys. The resulting topological superconductor features helical Majorana edge modes, leading to half-integer quantized spin-thermal Hall conductivity and to charge currents induced by circularly polarized light or other time-reversal symmetry-breaking fields.
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Affiliation(s)
- Valentin Crépel
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
| | - Daniele Guerci
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
| | - Jennifer Cano
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, New York 11794, USA
| | - J H Pixley
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
| | - Andrew Millis
- Center for Computational Quantum Physics, Flatiron Institute, New York, New York 10010, USA
- Department of Physics, Columbia University, New York, New York 10027, USA
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Guerci D, Wang J, Zang J, Cano J, Pixley JH, Millis A. Chiral Kondo lattice in doped MoTe 2/WSe 2 bilayers. SCIENCE ADVANCES 2023; 9:eade7701. [PMID: 36930704 PMCID: PMC10022889 DOI: 10.1126/sciadv.ade7701] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/07/2022] [Accepted: 02/10/2023] [Indexed: 06/18/2023]
Abstract
We theoretically study the interplay between magnetism and a heavy Fermi liquid in the AB-stacked transition metal dichalcogenide bilayer system, MoTe2/WSe2, in the regime in which the Mo layer supports localized magnetic moments coupled by interlayer electron tunneling to a weakly correlated band of itinerant electrons in the W layer. We show that the interlayer electron transfer leads to a chiral Kondo exchange, with consequences including a strong dependence of the Kondo temperature on carrier concentration and anomalous Hall effect due to a topological hybridization gap. The theoretical model exhibits two phases, a small Fermi surface magnet and a large Fermi surface heavy Fermi liquid; at the mean-field level, the transition between them is first order. Our results provide concrete experimental predictions for ongoing experiments on MoTe2/WSe2 bilayer heterostructures and introduces a controlled route to observe a topological selective Mott transition.
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Affiliation(s)
- Daniele Guerci
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY 10010, USA
| | - Jie Wang
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY 10010, USA
| | - Jiawei Zang
- Department of Physics, Columbia University, 538 West 120th Street, New York, NY 10027, USA
| | - Jennifer Cano
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY 10010, USA
- Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794, USA
| | - J. H. Pixley
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY 10010, USA
- Department of Physics and Astronomy, Center for Materials Theory, Rutgers University, Piscataway, NJ 08854, USA
| | - Andrew Millis
- Center for Computational Quantum Physics, Flatiron Institute, New York, NY 10010, USA
- Department of Physics, Columbia University, 538 West 120th Street, New York, NY 10027, USA
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