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Chang Y, Yi J, Wu AK, Kugler FB, Andrei EY, Vanderbilt D, Kotliar G, Pixley JH. Vacancy-Induced Tunable Kondo Effect in Twisted Bilayer Graphene. PHYSICAL REVIEW LETTERS 2024; 133:126503. [PMID: 39373443 DOI: 10.1103/physrevlett.133.126503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 07/03/2024] [Accepted: 08/18/2024] [Indexed: 10/08/2024]
Abstract
In single sheets of graphene, vacancy-induced states have been shown to host an effective spin-1/2 hole that can be Kondo screened at low temperatures. Here, we show how these vacancy-induced impurity states survive in twisted bilayer graphene (TBG), which thus provides a tunable system to probe the critical destruction of the Kondo effect in pseudogap hosts. Ab initio calculations and atomic-scale modeling are used to determine the nature of the vacancy states in the vicinity of the magic angle in TBG, demonstrating that the vacancy can be treated as a quantum impurity. Utilizing this insight, we construct an Anderson impurity model with a TBG host that we solve using the numerical renormalization group combined with the kernel polynomial method. We determine the phase diagram of the model and show how there is a strict dichotomy between vacancies in the AA/BB versus AB/BA tunneling regions. In AB/BA vacancies, the Kondo temperature at the magic angle develops a broad distribution with a tail to vanishing temperatures due to multifractal wave functions at the magic angle. We argue that scanning tunneling microscopy in the vicinity of the vacancy can act as a probe of both the critical single-particle states and the underlying many-body ground state in magic-angle TBG.
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Affiliation(s)
| | | | | | - Fabian B Kugler
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
| | | | | | - Gabriel Kotliar
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, USA
| | - J H Pixley
- Department of Physics and Astronomy, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Materials Theory, Rutgers University, Piscataway, New Jersey 08854, USA
- Center for Computational Quantum Physics, Flatiron Institute, 162 5th Avenue, New York, New York 10010, USA
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2
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Xiao Y, Wu J, Dadap JI, Awan KM, Yang D, Liang J, Watanabe K, Taniguchi T, Zonno M, Bluschke M, Eisaki H, Greven M, Damascelli A, Ye Z. Optically Probing Unconventional Superconductivity in Atomically Thin Bi 2Sr 2Ca 0.92Y 0.08Cu 2O 8+δ. NANO LETTERS 2024; 24:3986-3993. [PMID: 38501960 DOI: 10.1021/acs.nanolett.4c00559] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/20/2024]
Abstract
Atomically thin cuprates exhibiting a superconducting phase transition temperature similar to that of the bulk have recently been realized, although the device fabrication remains a challenge and limits the potential for many novel studies and applications. Here, we use an optical pump-probe approach to noninvasively study the unconventional superconductivity in atomically thin Bi2Sr2Ca0.92Y0.08Cu2O8+δ (Y-Bi2212). Apart from finding an optical response due to the superconducting phase transition that is similar to that of bulk Y-Bi2212, we observe that the sign and amplitude of the pump-probe signal in atomically thin flakes vary significantly in different dielectric environments depending on the nature of the optical excitation. By exploiting the spatial resolution of the optical probe, we uncover the exceptional sensitivity of monolayer Y-Bi2212 to the environment. Our results provide the first optical evidence for the intralayer nature of the superconducting condensate in Bi2212 and highlight the role of double-sided encapsulation in preserving superconductivity in atomically thin cuprates.
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Affiliation(s)
- Yunhuan Xiao
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jingda Wu
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jerry I Dadap
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Kashif Masud Awan
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Dongyang Yang
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Jing Liang
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Kenji Watanabe
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Takashi Taniguchi
- International Center for Materials Nanoarchitectonics, National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - Marta Zonno
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Martin Bluschke
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Hiroshi Eisaki
- Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8568, Japan
| | - Martin Greven
- School of Physics and Astronomy, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Andrea Damascelli
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
| | - Ziliang Ye
- Department of Physics & Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada
- Quantum Matter Institute, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
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3
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Zhao SYF, Cui X, Volkov PA, Yoo H, Lee S, Gardener JA, Akey AJ, Engelke R, Ronen Y, Zhong R, Gu G, Plugge S, Tummuru T, Kim M, Franz M, Pixley JH, Poccia N, Kim P. Time-reversal symmetry breaking superconductivity between twisted cuprate superconductors. Science 2023; 382:1422-1427. [PMID: 38060675 DOI: 10.1126/science.abl8371] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2021] [Accepted: 11/07/2023] [Indexed: 12/23/2023]
Abstract
Twisted interfaces between stacked van der Waals (vdW) cuprate crystals present a platform for engineering superconducting order parameters by adjusting stacking angles. Using a cryogenic assembly technique, we construct twisted vdW Josephson junctions (JJs) at atomically sharp interfaces between Bi2Sr2CaCu2O8+x crystals, with quality approaching the limit set by intrinsic JJs. Near 45° twist angle, we observe fractional Shapiro steps and Fraunhofer patterns, consistent with the existence of two degenerate Josephson ground states related by time-reversal symmetry (TRS). By programming the JJ current bias sequence, we controllably break TRS to place the JJ into either of the two ground states, realizing reversible Josephson diodes without external magnetic fields. Our results open a path to engineering topological devices at higher temperatures.
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Affiliation(s)
- S Y Frank Zhao
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Xiaomeng Cui
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Pavel A Volkov
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA
- Department of Physics, University of Connecticut, Storrs, CT 06269, USA
| | - Hyobin Yoo
- Department of Physics, Institute of Emergent Materials, Sogang University, Seoul 04107, Korea
| | - Sangmin Lee
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea
| | - Jules A Gardener
- Center for Nanoscale Systems, Harvard University, Cambridge, MA 02138, USA
| | - Austin J Akey
- Center for Nanoscale Systems, Harvard University, Cambridge, MA 02138, USA
| | - Rebecca Engelke
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Yuval Ronen
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
| | - Ruidan Zhong
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Genda Gu
- Department of Condensed Matter Physics and Materials Science, Brookhaven National Laboratory, Upton, NY 11973, USA
| | - Stephan Plugge
- Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Tarun Tummuru
- Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Miyoung Kim
- Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Korea
| | - Marcel Franz
- Department of Physics and Astronomy and Stewart Blusson Quantum Matter Institute, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Jedediah H Pixley
- Center for Materials Theory, Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854, USA
| | - Nicola Poccia
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
- Leibniz Institute for Solid State and Materials Research Dresden (IFW Dresden), 01069 Dresden, Germany
| | - Philip Kim
- Department of Physics, Harvard University, Cambridge, MA 02138, USA
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4
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Saggau CN, Shokri S, Martini M, Confalone T, Lee Y, Wolf D, Gu G, Brosco V, Montemurro D, Vinokur VM, Nielsch K, Poccia N. 2D High-Temperature Superconductor Integration in Contact Printed Circuit Boards. ACS APPLIED MATERIALS & INTERFACES 2023; 15:51558-51564. [PMID: 37878903 PMCID: PMC10637321 DOI: 10.1021/acsami.3c10564] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Accepted: 09/20/2023] [Indexed: 10/27/2023]
Abstract
Inherent properties of superconducting Bi2Sr2CaCu2O8+x films, such as the high superconducting transition temperature Tc, efficient Josephson coupling between neighboring CuO layers, and fast quasiparticle relaxation dynamics, make them a promising platform for advances in quantum computing and communication technologies. However, preserving two-dimensional superconductivity during device fabrication is an outstanding experimental challenge because of the fast degradation of the superconducting properties of two-dimensional flakes when they are exposed to moisture, organic solvents, and heat. Herein, to realize superconducting devices utilizing two-dimensional (2D) superconducting films, we develop a novel fabrication technique relying on the cryogenic dry transfer of printable circuits embedded into a silicon nitride membrane. This approach separates the circuit fabrication stage requiring chemically reactive substances and ionizing physical processes from the creation of the thin superconducting structures. Apart from providing electrical contacts in a single transfer step, the membrane encapsulates the surface of the crystal, shielding it from the environment. The fabricated atomically thin Bi2Sr2CaCu2O8+x-based devices show a high superconducting transition temperature of Tc ≃ 91 K close to that of the bulk crystal and demonstrate stable superconducting properties.
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Affiliation(s)
- Christian N. Saggau
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
| | - Sanaz Shokri
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
- Institute
of Applied Physics, Technische Universität
Dresden, 01062 Dresden, Germany
| | - Mickey Martini
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
- Institute
of Applied Physics, Technische Universität
Dresden, 01062 Dresden, Germany
| | - Tommaso Confalone
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
- Institute
of Applied Physics, Technische Universität
Dresden, 01062 Dresden, Germany
| | - Yejin Lee
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
- Institute
of Applied Physics, Technische Universität
Dresden, 01062 Dresden, Germany
| | - Daniel Wolf
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
| | - Genda Gu
- Condensed
Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Valentina Brosco
- Istituto
dei Sistemi Complessi (ISC-CNR) and Dipartimento di Fisica, Universita,
Sapienza, P.le A. Moro,
2, I-00185 Rome, Italy
- Centro Ricerche Enrico Fermi, Piazza del Viminale, 1, I-00184 Rome, Italy
| | - Domenico Montemurro
- Department
of Physics, University of Naples Federico
II, 80125 Naples, Italy
| | - Valerii M. Vinokur
- Terra Quantum
AG, CH-9000 St. Gallen, Switzerland
- Physics
Department, CUNY, City College of City University
of New York, 160 Convent Ave, New York, New York 10031, United States
| | - Kornelius Nielsch
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
- Institute
of Applied Physics, Technische Universität
Dresden, 01062 Dresden, Germany
- Institute
of Materials Science, Technische Universität
Dresden, 01062 Dresden, Germany
| | - Nicola Poccia
- Leibniz
Institute for Solid State and Materials Science Dresden (IFW Dresden), 01069 Dresden, Germany
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5
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Sukhachov PO, von Oppen F, Glazman LI. Andreev Reflection in Scanning Tunneling Spectroscopy of Unconventional Superconductors. PHYSICAL REVIEW LETTERS 2023; 130:216002. [PMID: 37295098 DOI: 10.1103/physrevlett.130.216002] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Accepted: 05/02/2023] [Indexed: 06/12/2023]
Abstract
We evaluate the differential conductance measured in an STM setting at arbitrary electron transmission between STM tip and a 2D superconductor with arbitrary gap structure. Our analytical scattering theory accounts for Andreev reflections, which become prominent at larger transmissions. We show that this provides complementary information about the superconducting gap structure beyond the tunneling density of states, strongly facilitating the ability to extract the gap symmetry and its relation to the underlying crystalline lattice. We use the developed theory to discuss recent experimental results on superconductivity in twisted bilayer graphene.
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Affiliation(s)
- P O Sukhachov
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
| | - Felix von Oppen
- Dahlem Center for Complex Quantum Systems and Fachbereich Physik, Freie Universität Berlin, 14195 Berlin, Germany
| | - L I Glazman
- Department of Physics, Yale University, New Haven, Connecticut 06520, USA
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