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Liu X, Chong YX, Sharma R, Davis JCS. Atomic-scale visualization of electronic fluid flow. Nat Mater 2021; 20:1480-1484. [PMID: 34462570 DOI: 10.1038/s41563-021-01077-1] [Citation(s) in RCA: 1] [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] [Received: 01/18/2021] [Accepted: 07/12/2021] [Indexed: 06/13/2023]
Abstract
The most essential characteristic of any fluid is the velocity field, and this is particularly true for macroscopic quantum fluids1. Although rapid advances2-7 have occurred in quantum fluid velocity field imaging8, the velocity field of a charged superfluid-a superconductor-has never been visualized. Here we use superconducting-tip scanning tunnelling microscopy9-11 to image the electron-pair density and velocity fields of the flowing electron-pair fluid in superconducting NbSe2. Imaging of the velocity fields surrounding a quantized vortex12,13 finds electronic fluid flow with speeds reaching 10,000 km h-1. Together with independent imaging of the electron-pair density via Josephson tunnelling, we visualize the supercurrent density, which peaks above 3 × 107 A cm-2. The spatial patterns in electronic fluid flow and magneto-hydrodynamics reveal hexagonal structures coaligned to the crystal lattice and quasiparticle bound states14, as long anticipated15-18. These techniques pave the way for electronic fluid flow visualization studies of other charged quantum fluids.
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Affiliation(s)
- Xiaolong Liu
- Department of Physics, Cornell University, Ithaca, NY, USA
| | - Yi Xue Chong
- Department of Physics, Cornell University, Ithaca, NY, USA
| | - Rahul Sharma
- Department of Physics, Cornell University, Ithaca, NY, USA
- Department of Physics, University of Maryland, College Park, MD, USA
| | - J C Séamus Davis
- Department of Physics, Cornell University, Ithaca, NY, USA.
- Department of Physics, University College Cork, Cork, Ireland.
- Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany.
- Clarendon Laboratory, University of Oxford, Oxford, UK.
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Wang S, Choubey P, Chong YX, Chen W, Ren W, Eisaki H, Uchida S, Hirschfeld PJ, Davis JCS. Scattering interference signature of a pair density wave state in the cuprate pseudogap phase. Nat Commun 2021; 12:6087. [PMID: 34667154 PMCID: PMC8526682 DOI: 10.1038/s41467-021-26028-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2021] [Accepted: 09/09/2021] [Indexed: 11/21/2022] Open
Abstract
An unidentified quantum fluid designated the pseudogap (PG) phase is produced by electron-density depletion in the CuO2 antiferromagnetic insulator. Current theories suggest that the PG phase may be a pair density wave (PDW) state characterized by a spatially modulating density of electron pairs. Such a state should exhibit a periodically modulating energy gap [Formula: see text] in real-space, and a characteristic quasiparticle scattering interference (QPI) signature [Formula: see text] in wavevector space. By studying strongly underdoped Bi2Sr2CaDyCu2O8 at hole-density ~0.08 in the superconductive phase, we detect the 8a0-periodic [Formula: see text] modulations signifying a PDW coexisting with superconductivity. Then, by visualizing the temperature dependence of this electronic structure from the superconducting into the pseudogap phase, we find the evolution of the scattering interference signature [Formula: see text] that is predicted specifically for the temperature dependence of an 8a0-periodic PDW. These observations are consistent with theory for the transition from a PDW state coexisting with d-wave superconductivity to a pure PDW state in the Bi2Sr2CaDyCu2O8 pseudogap phase.
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Affiliation(s)
- Shuqiu Wang
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Peayush Choubey
- Institut für Theoretische Physik III, Ruhr-Universität Bochum, Bochum, Germany
- Department of Physics, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand, India
| | - Yi Xue Chong
- LASSP, Department of Physics, Cornell University, Ithaca, NY, USA
| | - Weijiong Chen
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - Wangping Ren
- Clarendon Laboratory, University of Oxford, Oxford, UK
| | - H Eisaki
- Institute of Advanced Industrial Science and Tech., Tsukuba, Ibaraki, Japan
| | - S Uchida
- Institute of Advanced Industrial Science and Tech., Tsukuba, Ibaraki, Japan
| | | | - J C Séamus Davis
- Clarendon Laboratory, University of Oxford, Oxford, UK.
- LASSP, Department of Physics, Cornell University, Ithaca, NY, USA.
- Department of Physics, University College Cork, Cork, Ireland.
- Max-Planck Institute for Chemical Physics of Solids, Dresden, Germany.
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Abstract
Imaging an exotic state
Among the most intriguing of the many phases of cuprate superconductors is the so-called pair density wave (PDW) state. PDW is characterized by a spatially modulated density of Cooper pairs and can be detected with a scanning tunneling microscope equipped with a superconducting tip. Liu
et al.
used Josephson tunneling microscopy, modified for the task, to detect PDW in niobium diselenide, a superconductor with a layered hexagonal structure. The PDW state is expected to appear in other transition metal dichalcogenides as well.
Science
, abd4607, this issue p.
1447
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Affiliation(s)
- Xiaolong Liu
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14850, USA
| | - Yi Xue Chong
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14850, USA
| | - Rahul Sharma
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14850, USA
- Department of Physics, University of Maryland, College Park, MD 20740, USA
| | - J. C. Séamus Davis
- Laboratory of Atomic and Solid State Physics, Department of Physics, Cornell University, Ithaca, NY 14850, USA
- Department of Physics, University College Cork, Cork T12 R5C, Ireland
- Max Planck Institute for Chemical Physics of Solids, D-01187 Dresden, Germany
- Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, UK
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Chong YX, Liu X, Sharma R, Kostin A, Gu G, Fujita K, Davis JCS, Sprau PO. Severe Dirac Mass Gap Suppression in Sb 2Te 3-Based Quantum Anomalous Hall Materials. Nano Lett 2020; 20:8001-8007. [PMID: 32985892 DOI: 10.1021/acs.nanolett.0c02873] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The quantum anomalous Hall (QAH) effect appears in ferromagnetic topological insulators (FMTIs) when a Dirac mass gap opens in the spectrum of the topological surface states (SSs). Unaccountably, although the mean mass gap can exceed 28 meV (or ∼320 K), the QAH effect is frequently only detectable at temperatures below 1 K. Using atomic-resolution Landau level spectroscopic imaging, we compare the electronic structure of the archetypal FMTI Cr0.08(Bi0.1Sb0.9)1.92Te3 to that of its nonmagnetic parent (Bi0.1Sb0.9)2Te3, to explore the cause. In (Bi0.1Sb0.9)2Te3, we find spatially random variations of the Dirac energy. Statistically equivalent Dirac energy variations are detected in Cr0.08(Bi0.1Sb0.9)1.92Te3 with concurrent but uncorrelated Dirac mass gap disorder. These two classes of SS electronic disorder conspire to drastically suppress the minimum mass gap to below 100 μeV for nanoscale regions separated by <1 μm. This fundamentally limits the fully quantized anomalous Hall effect in Sb2Te3-based FMTI materials to very low temperatures.
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Affiliation(s)
- Yi Xue Chong
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
- CMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Xiaolong Liu
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
- Kavli Institute at Cornell, Cornell University, Ithaca, New York 14853, United States
| | - Rahul Sharma
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
- CMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - Andrey Kostin
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
| | - Genda Gu
- CMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - K Fujita
- CMPMS Department, Brookhaven National Laboratory, Upton, New York 11973, United States
| | - J C Séamus Davis
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
- Department of Physics, University College Cork, Cork T12R5C, Ireland
- Clarendon Laboratory, University of Oxford, Oxford OX1 3PU, U.K
| | - Peter O Sprau
- LASSP, Department of Physics, Cornell University, Ithaca, New York 14853, United States
- Advanced Development Center, ASML, Wilton, Connecticut 06897, United States
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Kostin A, Sprau PO, Kreisel A, Chong YX, Böhmer AE, Canfield PC, Hirschfeld PJ, Andersen BM, Davis JCS. Imaging orbital-selective quasiparticles in the Hund's metal state of FeSe. Nat Mater 2018; 17:869-874. [PMID: 30177690 DOI: 10.1038/s41563-018-0151-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Accepted: 07/24/2018] [Indexed: 06/08/2023]
Abstract
Strong electronic correlations, emerging from the parent Mott insulator phase, are key to copper-based high-temperature superconductivity. By contrast, the parent phase of an iron-based high-temperature superconductor is never a correlated insulator. However, this distinction may be deceptive because Fe has five actived d orbitals while Cu has only one. In theory, such orbital multiplicity can generate a Hund's metal state, in which alignment of the Fe spins suppresses inter-orbital fluctuations, producing orbitally selective strong correlations. The spectral weights Zm of quasiparticles associated with different Fe orbitals m should then be radically different. Here we use quasiparticle scattering interference resolved by orbital content to explore these predictions in FeSe. Signatures of strong, orbitally selective differences of quasiparticle Zm appear on all detectable bands over a wide energy range. Further, the quasiparticle interference amplitudes reveal that [Formula: see text], consistent with earlier orbital-selective Cooper pairing studies. Thus, orbital-selective strong correlations dominate the parent state of iron-based high-temperature superconductivity in FeSe.
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Affiliation(s)
- A Kostin
- Department of Physics, Cornell University, Ithaca, NY, USA
- CMPMS Department, Brookhaven National Laboratory, Upton, NY, USA
| | - P O Sprau
- Department of Physics, Cornell University, Ithaca, NY, USA
- CMPMS Department, Brookhaven National Laboratory, Upton, NY, USA
| | - A Kreisel
- Institut für Theoretische Physik, Universität Leipzig, Leipzig, Germany
| | - Yi Xue Chong
- Department of Physics, Cornell University, Ithaca, NY, USA
- CMPMS Department, Brookhaven National Laboratory, Upton, NY, USA
| | - A E Böhmer
- Ames Laboratory, U.S. Department of Energy, Ames, IA, USA
- Karlsruhe Institute of Technology, Karlsruhe, Germany
| | - P C Canfield
- Ames Laboratory, U.S. Department of Energy, Ames, IA, USA
- Department of Physics and Astronomy, Iowa State University, Ames, IA, USA
| | - P J Hirschfeld
- Department of Physics, University of Florida, Gainesville, FL, USA
| | - B M Andersen
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - J C Séamus Davis
- Department of Physics, Cornell University, Ithaca, NY, USA.
- CMPMS Department, Brookhaven National Laboratory, Upton, NY, USA.
- School of Physics and Astronomy, University of St. Andrews, Fife, UK.
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