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Ge JF, Bastiaans KM, Chatzopoulos D, Cho D, Tromp WO, Benschop T, Niu J, Gu G, Allan MP. Single-electron charge transfer into putative Majorana and trivial modes in individual vortices. Nat Commun 2023; 14:3341. [PMID: 37286552 DOI: 10.1038/s41467-023-39109-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 05/25/2023] [Indexed: 06/09/2023] Open
Abstract
Majorana bound states are putative collective excitations in solids that exhibit the self-conjugate property of Majorana fermions-they are their own antiparticles. In iron-based superconductors, zero-energy states in vortices have been reported as potential Majorana bound states, but the evidence remains controversial. Here, we use scanning tunneling noise spectroscopy to study the tunneling process into vortex bound states in the conventional superconductor NbSe2, and in the putative Majorana platform FeTe0.55Se0.45. We find that tunneling into vortex bound states in both cases exhibits charge transfer of a single electron charge. Our data for the zero-energy bound states in FeTe0.55Se0.45 exclude the possibility of Yu-Shiba-Rusinov states and are consistent with both Majorana bound states and trivial vortex bound states. Our results open an avenue for investigating the exotic states in vortex cores and for future Majorana devices, although further theoretical investigations involving charge dynamics and superconducting tips are necessary.
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Affiliation(s)
- Jian-Feng Ge
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands
| | - Koen M Bastiaans
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, 2628 CJ, Delft, The Netherlands
| | | | - Doohee Cho
- Department of Physics, Yonsei University, Seoul, 03722, Republic of Korea
| | - Willem O Tromp
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands
| | - Tjerk Benschop
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands
| | - Jiasen Niu
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands
| | - Genda Gu
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, 2333 CA, Leiden, The Netherlands.
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Tromp WO, Benschop T, Ge JF, Battisti I, Bastiaans KM, Chatzopoulos D, Vervloet AHM, Smit S, van Heumen E, Golden MS, Huang Y, Kondo T, Takeuchi T, Yin Y, Hoffman JE, Sulangi MA, Zaanen J, Allan MP. Puddle formation and persistent gaps across the non-mean-field breakdown of superconductivity in overdoped (Pb,Bi) 2Sr 2CuO 6+δ. Nat Mater 2023; 22:703-709. [PMID: 36879002 DOI: 10.1038/s41563-023-01497-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Accepted: 01/31/2023] [Indexed: 06/03/2023]
Abstract
The cuprate high-temperature superconductors exhibit many unexplained electronic phases, but the superconductivity at high doping is often believed to be governed by conventional mean-field Bardeen-Cooper-Schrieffer theory1. However, it was shown that the superfluid density vanishes when the transition temperature goes to zero2,3, in contradiction to expectations from Bardeen-Cooper-Schrieffer theory. Our scanning tunnelling spectroscopy measurements in the overdoped regime of the (Pb,Bi)2Sr2CuO6+δ high-temperature superconductor show that this is due to the emergence of nanoscale superconducting puddles in a metallic matrix4,5. Our measurements further reveal that this puddling is driven by gap filling instead of gap closing. The important implication is that it is not a diminishing pairing interaction that causes the breakdown of superconductivity. Unexpectedly, the measured gap-to-filling correlation also reveals that pair breaking by disorder does not play a dominant role and that the mechanism of superconductivity in overdoped cuprate superconductors is qualitatively different from conventional mean-field theory.
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Affiliation(s)
- Willem O Tromp
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Tjerk Benschop
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Jian-Feng Ge
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Irene Battisti
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
| | - Koen M Bastiaans
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands
- Department of Quantum Nanoscience, Kavli Institute of Nanoscience, Delft University of Technology, Delft, The Netherlands
| | | | | | - Steef Smit
- Institute of Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - Erik van Heumen
- Institute of Physics, University of Amsterdam, Amsterdam, The Netherlands
- QuSoft, Amsterdam, The Netherlands
| | - Mark S Golden
- Institute of Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - Yinkai Huang
- Institute of Physics, University of Amsterdam, Amsterdam, The Netherlands
| | - Takeshi Kondo
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan
| | | | - Yi Yin
- Zhejiang Province Key Laboratory of Quantum Technology and Device, Department of Physics, Zhejiang University, Hangzhou, China
- Collaborative Innovation Centre of Advanced Microstructures, Nanjing University, Nanjiang, China
| | | | - Miguel Antonio Sulangi
- Department of Physics, University of Florida, Gainesville, FL, USA
- National Institute of Physics, College of Science, University of the Philippines, Diliman, Quezon City, Philippines
| | - Jan Zaanen
- Institute-Lorentz for Theoretical Physics, Leiden University, Leiden, The Netherlands
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, Leiden, The Netherlands.
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de Jong TA, Benschop T, Chen X, Krasovskii EE, de Dood MJA, Tromp RM, Allan MP, van der Molen SJ. Imaging moiré deformation and dynamics in twisted bilayer graphene. Nat Commun 2022; 13:70. [PMID: 35013349 PMCID: PMC8748992 DOI: 10.1038/s41467-021-27646-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2021] [Accepted: 12/03/2021] [Indexed: 11/22/2022] Open
Abstract
In 'magic angle' twisted bilayer graphene (TBG) a flat band forms, yielding correlated insulator behavior and superconductivity. In general, the moiré structure in TBG varies spatially, influencing the overall conductance properties of devices. Hence, to understand the wide variety of phase diagrams observed, a detailed understanding of local variations is needed. Here, we study spatial and temporal variations of the moiré pattern in TBG using aberration-corrected Low Energy Electron Microscopy (AC-LEEM). We find a smaller spatial variation than reported previously. Furthermore, we observe thermal fluctuations corresponding to collective atomic displacements over 70 pm on a timescale of seconds. Remarkably, no untwisting is found up to 600 ∘C. We conclude that thermal annealing can be used to decrease local disorder. Finally, we observe edge dislocations in the underlying atomic lattice, the moiré structure acting as a magnifying glass. These topological defects are anticipated to exhibit unique local electronic properties.
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Affiliation(s)
- Tobias A de Jong
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands.
| | - Tjerk Benschop
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Xingchen Chen
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Eugene E Krasovskii
- Departamento de Polímeros y Materiales Avanzados: Física, Química y Tecnología, Universidad del Pais Vasco UPV/EHU, 20080, San Sebastián/Donostia, Spain
- IKERBASQUE, Basque Foundation for Science, E-48013, Bilbao, Spain
- Donostia International Physics Center (DIPC), E-20018, San Sebastián, Spain
| | - Michiel J A de Dood
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Rudolf M Tromp
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
- IBM T.J.Watson Research Center, 1101 Kitchawan Road, P.O. Box 218, Yorktown Heights, New York, NY, 10598, USA
| | - Milan P Allan
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands
| | - Sense Jan van der Molen
- Leiden Institute of Physics, Leiden University, P.O. Box 9504, 2300 RA, Leiden, The Netherlands.
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Leeuwenhoek M, Groenewoud F, van Oosten K, Benschop T, Allan MP, Gröblacher S. Fabrication of on-chip probes for double-tip scanning tunneling microscopy. Microsyst Nanoeng 2020; 6:99. [PMID: 34567708 PMCID: PMC8433193 DOI: 10.1038/s41378-020-00209-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 08/28/2020] [Accepted: 09/01/2020] [Indexed: 05/22/2023]
Abstract
A reduction of the interprobe distance in multiprobe and double-tip scanning tunneling microscopy to the nanometer scale has been a longstanding and technically difficult challenge. Recent multiprobe systems have allowed for significant progress by achieving distances of ~30 nm using two individually driven, traditional metal wire tips. For situations where simple alignment and fixed separation can be advantageous, we present the fabrication of on-chip double-tip devices that incorporate two mechanically fixed gold tips with a tip separation of only 35 nm. We utilize the excellent mechanical, insulating and dielectric properties of high-quality SiN as a base material to realize easy-to-implement, lithographically defined and mechanically stable tips. With their large contact pads and adjustable footprint, these novel tips can be easily integrated with most existing commercial combined STM/AFM systems.
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Affiliation(s)
- Maarten Leeuwenhoek
- Kavli Institute of Nanoscience, Department of Quantum Nanoscience, Delft University of Technology, Lorentzweg 1, 2628CJ Delft, The Netherlands
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
| | - Freek Groenewoud
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
| | - Kees van Oosten
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
| | - Tjerk Benschop
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
| | - Milan P. Allan
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333CA Leiden, The Netherlands
| | - Simon Gröblacher
- Kavli Institute of Nanoscience, Department of Quantum Nanoscience, Delft University of Technology, Lorentzweg 1, 2628CJ Delft, The Netherlands
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Bastiaans KM, Benschop T, Chatzopoulos D, Cho D, Dong Q, Jin Y, Allan MP. Amplifier for scanning tunneling microscopy at MHz frequencies. Rev Sci Instrum 2018; 89:093709. [PMID: 30278769 DOI: 10.1063/1.5043267] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Accepted: 09/09/2018] [Indexed: 06/08/2023]
Abstract
Conventional scanning tunneling microscopy (STM) is limited to a bandwidth of a few kHz around DC. Here, we develop, build, and test a novel amplifier circuit capable of measuring the tunneling current in the MHz regime while simultaneously performing conventional STM measurements. This is achieved with an amplifier circuit including a LC tank with a quality factor exceeding 600 and a home-built, low-noise high electron mobility transistor. The amplifier circuit functions while simultaneously scanning with atomic resolution in the tunneling regime, i.e., at junction resistances in the range of giga-ohms, and down towards point contact spectroscopy. To enable high signal-to-noise ratios and meet all technical requirements for the inclusion in a commercial low temperature, ultra-high vacuum STM, we use superconducting cross-wound inductors and choose materials and circuit elements with low heat load. We demonstrate the high performance of the amplifier by spatially mapping the Poissonian noise of tunneling electrons on an atomically clean Au(111) surface. We also show differential conductance spectroscopy measurements at 3 MHz, demonstrating superior performance over conventional spectroscopy techniques. Further, our technology could be used to perform impedance matched spin resonance and distinguish Majorana modes from more conventional edge states.
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Affiliation(s)
- K M Bastiaans
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - T Benschop
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - D Chatzopoulos
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - D Cho
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
| | - Q Dong
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - Y Jin
- Centre de Nanosciences et de Nanotechnologies, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay, C2N-Marcoussis, 91460 Marcoussis, France
| | - M P Allan
- Leiden Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden, The Netherlands
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