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Razmadze D, O'Farrell ECT, Krogstrup P, Marcus CM. Quantum Dot Parity Effects in Trivial and Topological Josephson Junctions. Phys Rev Lett 2020; 125:116803. [PMID: 32975997 DOI: 10.1103/physrevlett.125.116803] [Citation(s) in RCA: 2] [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: 05/24/2020] [Accepted: 08/10/2020] [Indexed: 06/11/2023]
Abstract
An odd-occupied quantum dot in a Josephson junction can flip transmission phase, creating a π junction. When the junction couples topological superconductors, no phase flip is expected. We investigate this and related effects in a full-shell hybrid interferometer, using gate voltage to control dot-junction parity and axial magnetic flux to control the transition from trivial to topological superconductivity. Enhanced zero-bias conductance and critical current for odd parity in the topological phase reflects hybridization of the confined spin with zero-energy modes in the leads.
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Affiliation(s)
- D Razmadze
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
| | - E C T O'Farrell
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
| | - P Krogstrup
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Materials Lab-Copenhagen, 2800 Kongens Lyngby, Denmark
| | - C M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
- Microsoft Quantum Lab-Copenhagen, 2100 Copenhagen, Denmark
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2
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Whiticar AM, Fornieri A, O'Farrell ECT, Drachmann ACC, Wang T, Thomas C, Gronin S, Kallaher R, Gardner GC, Manfra MJ, Marcus CM, Nichele F. Coherent transport through a Majorana island in an Aharonov-Bohm interferometer. Nat Commun 2020; 11:3212. [PMID: 32587242 PMCID: PMC7316771 DOI: 10.1038/s41467-020-16988-x] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Accepted: 05/17/2020] [Indexed: 11/29/2022] Open
Abstract
Majorana zero modes are leading candidates for topological quantum computation due to non-local qubit encoding and non-abelian exchange statistics. Spatially separated Majorana modes are expected to allow phase-coherent single-electron transport through a topological superconducting island via a mechanism referred to as teleportation. Here we experimentally investigate such a system by patterning an elongated epitaxial InAs-Al island embedded in an Aharonov-Bohm interferometer. With increasing parallel magnetic field, a discrete sub-gap state in the island is lowered to zero energy yielding persistent 1e-periodic Coulomb blockade conductance peaks (e is the elementary charge). In this condition, conductance through the interferometer is observed to oscillate in a perpendicular magnetic field with a flux period of h/e (h is Planck’s constant), indicating coherent transport of single electrons through the islands, a signature of electron teleportation via Majorana modes. Theories predict teleportation of phase-coherent single electrons through a topological superconducting island. Here, the authors report persistent Coulomb blockade conductance peaks due to coherent transport of single electrons through patterned InAs-Al islands embedded in an Aharonov-Bohm interferometer.
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Affiliation(s)
- A M Whiticar
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - A Fornieri
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - E C T O'Farrell
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - A C C Drachmann
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark
| | - T Wang
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - C Thomas
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - S Gronin
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - R Kallaher
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - G C Gardner
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA
| | - M J Manfra
- Department of Physics and Astronomy and Microsoft Quantum Lab Purdue, Purdue University, West Lafayette, IN, 47907, USA.,Birck Nanotechnology Center, Purdue University, West Lafayette, IN, 47907, USA.,School of Materials Engineering, Purdue University, West Lafayette, IN, 47907, USA.,School of Electrical and Computer Engineering, Purdue University, West Lafayette, IN, 47907, USA
| | - C M Marcus
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark.
| | - F Nichele
- Center for Quantum Devices, Niels Bohr Institute, University of Copenhagen and Microsoft Quantum Lab Copenhagen, Universitetsparken 5, Copenhagen, 2100, Denmark. .,IBM Research - Zurich, Sumerstrasse 4, 8803, Rschlikon, Switzerland.
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O'Farrell ECT, Drachmann ACC, Hell M, Fornieri A, Whiticar AM, Hansen EB, Gronin S, Gardner GC, Thomas C, Manfra MJ, Flensberg K, Marcus CM, Nichele F. Hybridization of Subgap States in One-Dimensional Superconductor-Semiconductor Coulomb Islands. Phys Rev Lett 2018; 121:256803. [PMID: 30608825 DOI: 10.1103/physrevlett.121.256803] [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: 04/25/2018] [Indexed: 06/09/2023]
Abstract
We present measurements of one-dimensional superconductor-semiconductor Coulomb islands, fabricated by gate confinement of a two-dimensional InAs heterostructure with an epitaxial Al layer. When tuned via electrostatic side gates to regimes without subgap states, Coulomb blockade reveals Cooper-pair mediated transport. When subgap states are present, Coulomb peak positions and heights oscillate in a correlated way with magnetic field and gate voltage, as predicted theoretically, with (anti)crossings in (parallel) transverse magnetic field indicating Rashba-type spin-orbit coupling. Overall results are consistent with a picture of overlapping Majorana zero modes in finite wires.
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Affiliation(s)
- E C T O'Farrell
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A C C Drachmann
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - M Hell
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
- Division of Solid State Physics and NanoLund, Lund University, Box 118, S-22100 Lund, Sweden
| | - A Fornieri
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - A M Whiticar
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - E B Hansen
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - S Gronin
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - G C Gardner
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - C Thomas
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
| | - M J Manfra
- Department of Physics and Astronomy and Station Q Purdue, Purdue University, West Lafayette, Indiana 47907, USA
- Birck Nanotechnology Center, Purdue University, West Lafayette, Indiana 47907, USA
- School of Materials Engineering, Purdue University, West Lafayette, Indiana 47907, USA
- School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907, USA
| | - K Flensberg
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - C M Marcus
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
| | - F Nichele
- Center for Quantum Devices and Station Q Copenhagen, Niels Bohr Institute, University of Copenhagen, Universitetsparken 5, 2100 Copenhagen, Denmark
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O'Farrell ECT, Tan JY, Yeo Y, Koon GKW, Özyilmaz B, Watanabe K, Taniguchi T. Rashba Interaction and Local Magnetic Moments in a Graphene-BN Heterostructure Intercalated with Au. Phys Rev Lett 2016; 117:076603. [PMID: 27563982 DOI: 10.1103/physrevlett.117.076603] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Indexed: 06/06/2023]
Abstract
We intercalate a van der Waals heterostructure of graphene and hexagonal boron nitride with Au, by encapsulation, and show that the Au at the interface is two dimensional. Charge transfer upon current annealing indicates the redistribution of the Au and induces splitting of the graphene band structure. The effect of an in-plane magnetic field confirms that the splitting is due to spin splitting and that the spin polarization is in the plane, characteristic of a Rashba interaction with a magnitude of approximately 25 meV. Consistent with the presence of an intrinsic interfacial electric field we show that the splitting can be enhanced by an applied displacement field in dual gated samples. A giant negative magnetoresistance, up to 75%, and a field induced anomalous Hall effect at magnetic fields <1 T are observed. These demonstrate that the hybridized Au has a magnetic moment and suggests the proximity to the formation of a collective magnetic phase. These effects persist close to room temperature.
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Affiliation(s)
- E C T O'Farrell
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore and Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - J Y Tan
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore and Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - Y Yeo
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore and Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - G K W Koon
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore and Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - B Özyilmaz
- Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore 117546, Singapore and Department of Physics, National University of Singapore, Singapore 117542, Singapore
| | - K Watanabe
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
| | - T Taniguchi
- National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044, Japan
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O'Farrell ECT, Avsar A, Tan JY, Eda G, Özyilmaz B. Quantum Transport Detected by Strong Proximity Interaction at a Graphene-WS2 van der Waals Interface. Nano Lett 2015; 15:5682-5688. [PMID: 26258760 DOI: 10.1021/acs.nanolett.5b01128] [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] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Magnetotransport measurements demonstrate that graphene in a van der Waals heterostructure is a sensitive probe of quantum transport in an adjacent WS2 layer via strong Coulomb interactions. We observe a large low-field magnetoresistance (≫ e(2)/h) and a -ln T temperature dependence of the resistance. In-plane magnetic field resistance indicates the origin is orbital and nonclassical. We demonstrate a strong electron-hole asymmetry in the mobility and coherence length of graphene demonstrating the presence of localized Coulomb interactions with ionized donors in the WS2 substrate, which ultimately leads to screening as the Fermi level of graphene is tuned toward the conduction band of WS2. This leads us to conclude that graphene couples to quantum localization processes in WS2 via the Coulomb interaction and results in the observed signatures of quantum transport. Our results show that theoretical descriptions of the van der Waals interface should not ignore localized strong correlations.
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Affiliation(s)
- E C T O'Farrell
- Centre for Advanced 2D Materials, National University of Singapore , Singapore 117546, Singapore
| | - A Avsar
- Centre for Advanced 2D Materials, National University of Singapore , Singapore 117546, Singapore
| | - J Y Tan
- Centre for Advanced 2D Materials, National University of Singapore , Singapore 117546, Singapore
| | - G Eda
- Centre for Advanced 2D Materials, National University of Singapore , Singapore 117546, Singapore
| | - B Özyilmaz
- Centre for Advanced 2D Materials, National University of Singapore , Singapore 117546, Singapore
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O'Farrell ECT, Matsumoto Y, Nakatsuji S. Evolution of c-f hybridization and two-component Hall effect in β-YbAlB4. Phys Rev Lett 2012; 109:176405. [PMID: 23215210 DOI: 10.1103/physrevlett.109.176405] [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: 08/13/2012] [Indexed: 06/01/2023]
Abstract
β-YbAlB(4) is the unique heavy fermion superconductor that exhibits unconventional quantum criticality without tuning in a strongly intermediate valence state. Despite the large coherence temperature, set by the peak of the longitudinal resistivity, our Hall effect measurements reveal that resonant skew scattering from incoherent local moments persists down to at least ~40 K, where the Hall coefficient exhibits a distinct minimum signaling another formation of coherence. The observation strongly suggests that the hybridization between f moments and conduction electrons has a two-component character with distinct Kondo or coherence scales T(K) of ~40 K and 200 K; this is confirmed by the magnetic field dependence of ρ(xy).
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Affiliation(s)
- E C T O'Farrell
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Japan 277-8581.
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Mercure JF, Goh SK, O'Farrell ECT, Perry RS, Sutherland ML, Rost AW, Grigera SA, Borzi RA, Gegenwart P, Mackenzie AP. Quantum oscillations in the anomalous phase in Sr3Ru2O7. Phys Rev Lett 2009; 103:176401. [PMID: 19905773 DOI: 10.1103/physrevlett.103.176401] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2009] [Indexed: 05/28/2023]
Abstract
We report measurements of quantum oscillations detected in the putative nematic phase of Sr3Ru2O7. Improvements in sample purity enabled the resolution of small amplitude de Haas-van Alphen (dHvA) oscillations between two first order metamagnetic transitions delimiting the phase. Two distinct frequencies were observed, whose amplitudes follow the normal Lifshitz-Kosevich profile. Variations of the dHvA frequencies are explained in terms of a chemical potential shift produced by reaching a peak in the density of states, and an anomalous field dependence of the oscillatory amplitude provides information on domains.
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Affiliation(s)
- J-F Mercure
- Scottish Universities Physics Alliance (SUPA), School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews KY16 9SS, United Kingdom
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O'Farrell ECT, Tompsett DA, Sebastian SE, Harrison N, Capan C, Balicas L, Kuga K, Matsuo A, Kindo K, Tokunaga M, Nakatsuji S, Csányi G, Fisk Z, Sutherland ML. Role of f electrons in the Fermi surface of the heavy fermion superconductor beta-YbAlB4. Phys Rev Lett 2009; 102:216402. [PMID: 19519118 DOI: 10.1103/physrevlett.102.216402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Indexed: 05/27/2023]
Abstract
We present a detailed quantum oscillation study of the Fermi surface of the recently discovered Yb-based heavy fermion superconductor beta-YbAlB4. We compare the data, obtained at fields from 10 to 45 T, to band structure calculations performed using the local density approximation. Analysis of the data suggests that f holes participate in the Fermi surface up to the highest magnetic fields studied. We comment on the significance of these findings for the unconventional superconducting properties of this material.
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Affiliation(s)
- E C T O'Farrell
- Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE, United Kingdom
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Goh SK, Paglione J, Sutherland M, O'Farrell ECT, Bergemann C, Sayles TA, Maple MB. Fermi-surface reconstruction in CeRh1-xCoxIn5. Phys Rev Lett 2008; 101:056402. [PMID: 18764411 DOI: 10.1103/physrevlett.101.056402] [Citation(s) in RCA: 3] [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: 03/26/2008] [Indexed: 05/26/2023]
Abstract
The evolution of the Fermi surface of CeRh(1-x)CoxIn5 was studied as a function of Co concentration x via measurements of the de Haas-van Alphen effect. By measuring the angular dependence of quantum oscillation frequencies, we identify a Fermi-surface sheet with f-electron character which undergoes an abrupt change in topology as x is varied. Surprisingly, this reconstruction does not occur at the quantum critical concentration x(c), where antiferromagnetism is suppressed to T=0. Instead we establish that this sudden change occurs well below x(c), at the concentration x approximately 0.4, where long-range magnetic order alters its character and superconductivity appears. Across all concentrations, the cyclotron effective mass of this sheet does not diverge, suggesting that critical behavior is not exhibited equally on all parts of the Fermi surface.
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Affiliation(s)
- Swee K Goh
- Cavendish Laboratory, University of Cambridge, J.J. Thomson Avenue, Cambridge, United Kingdom
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