51
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Liebhaber E, Acero González S, Baba R, Reecht G, Heinrich BW, Rohlf S, Rossnagel K, von Oppen F, Franke KJ. Yu-Shiba-Rusinov States in the Charge-Density Modulated Superconductor NbSe 2. NANO LETTERS 2020; 20:339-344. [PMID: 31842547 DOI: 10.1021/acs.nanolett.9b03988] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
NbSe2 is a remarkable superconductor in which charge-density order coexists with pairing correlations at low temperatures. Here, we study the interplay of magnetic adatoms and their Yu-Shiba-Rusinov (YSR) bound states with the charge density order. Exploiting the incommensurate nature of the charge-density wave (CDW), our measurements provide a thorough picture of how the CDW affects both the energies and the wave functions of the YSR states. Key features of the dependence of the YSR states on adsorption site relative to the CDW are explained by model calculations. Several properties make NbSe2 a promising substrate for realizing topological nanostructures. Our results will be important in designing such systems.
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Affiliation(s)
| | | | | | | | | | - Sebastian Rohlf
- Ruprecht-Haensel-Labor and Institut für Experimentelle und Angewandte Physik , Christian-Albrechts-Universität zu Kiel , 24098 Kiel , Germany
| | - Kai Rossnagel
- Ruprecht-Haensel-Labor and Institut für Experimentelle und Angewandte Physik , Christian-Albrechts-Universität zu Kiel , 24098 Kiel , Germany
- Deutsches Elektronen-Synchrotron DESY , 22607 Hamburg , Germany
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52
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Wang Z, Rodriguez JO, Jiao L, Howard S, Graham M, Gu GD, Hughes TL, Morr DK, Madhavan V. Evidence for dispersing 1D Majorana channels in an iron-based superconductor. Science 2020; 367:104-108. [DOI: 10.1126/science.aaw8419] [Citation(s) in RCA: 80] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2019] [Revised: 07/20/2019] [Accepted: 11/14/2019] [Indexed: 02/02/2023]
Abstract
The possible realization of Majorana fermions as quasiparticle excitations in condensed-matter physics has created much excitement. Most studies have focused on Majorana bound states; however, propagating Majorana states with linear dispersion have also been predicted. Here, we report scanning tunneling spectroscopic measurements of crystalline domain walls (DWs) in FeSe0.45Te0.55. We located DWs across which the lattice structure shifts by half a unit cell. These DWs have a finite, flat density of states inside the superconducting gap, which is a hallmark of linearly dispersing modes in one dimension. This signature is absent in DWs in the related superconductor, FeSe, which is not in the topological phase. Our combined data are consistent with the observation of dispersing Majorana states at a π-phase shift DW in a proximitized topological material.
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53
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Abstract
Atomic manipulation techniques have provided a bottom-up approach to investigating the unconventional properties and complex phases of strongly correlated electron materials. By engineering artificial systems containing tens to thousands of atoms with tailored electronic or magnetic properties, it has become possible to explore how quantum many-body effects emerge as the size of a system is increased from the nanoscale to the mesoscale. Here we investigate both theoretically and experimentally the quantum engineering of nanoscale Kondo lattices – Kondo droplets – exemplifying nanoscopic replicas of heavy-fermion materials. We demonstrate that by changing a droplet’s real-space geometry, we can not only create coherently coupled Kondo droplets whose properties asymptotically approach those of a quantum-coherent Kondo lattice, but also markedly increase or decrease the droplet’s Kondo temperature. Furthermore we report on the discovery of a new quantum phenomenon – the Kondo echo – a signature of droplets containing Kondo holes functioning as direct probes of spatially extended, quantum-coherent Kondo cloud correlations. The mechanism underlying screening of a Kondo lattice of magnetic moments by conduction electrons is an important unsolved problem. Figgins et al. use STM techniques to assemble nanoscale Kondo droplets that extrapolate between a single moment and the Kondo lattice, providing a platform for further study.
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54
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Kotetes P, Mercaldo MT, Cuoco M. Synthetic Weyl Points and Chiral Anomaly in Majorana Devices with Nonstandard Andreev-Bound-State Spectra. PHYSICAL REVIEW LETTERS 2019; 123:126802. [PMID: 31633965 DOI: 10.1103/physrevlett.123.126802] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2019] [Revised: 08/10/2019] [Indexed: 06/10/2023]
Abstract
We demonstrate how to design various nonstandard types of Andreev-bound-state (ABS) dispersions, via a composite construction relying on Majorana bound states (MBSs). Here, the MBSs appear at the interface of a Josephson junction consisting of two topological superconductors (TSCs). Each TSC harbors multiple MBSs per edge by virtue of a chiral or unitary symmetry. We find that, while the ABS dispersions are 2π periodic, they still contain multiple crossings which are protected by the conservation of fermion parity. A single junction with four interface MBSs and all MBS couplings fully controllable, or networks of such coupled junctions with partial coupling tunability, open the door for topological band structures with Weyl points or nodes in synthetic dimensions, which in turn allow for fermion-parity (FP) pumping with a cycle set by the ABS-dispersion details. In fact, in the case of nodes, the FP pumping is a manifestation of chiral anomaly in 2D synthetic spacetime. The possible experimental demonstration of ABS engineering in these devices further promises to unveil new paths for the detection of MBSs and higher-dimensional chiral anomaly.
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Affiliation(s)
- Panagiotis Kotetes
- CAS Key Laboratory of Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190, China
- Niels Bohr Institute, University of Copenhagen, 2100 Copenhagen, Denmark
| | - Maria Teresa Mercaldo
- Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, IT-84084 Fisciano (SA), Italy
| | - Mario Cuoco
- Dipartimento di Fisica "E. R. Caianiello," Università di Salerno, IT-84084 Fisciano (SA), Italy
- CNR-SPIN, IT-84084 Fisciano (SA), Italy
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55
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Delocalisation of Majorana quasiparticles in plaquette-nanowire hybrid system. Sci Rep 2019; 9:12933. [PMID: 31506461 PMCID: PMC6737171 DOI: 10.1038/s41598-019-49227-5] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Accepted: 07/31/2019] [Indexed: 11/09/2022] Open
Abstract
Interplay between superconductivity, spin-orbit coupling and magnetic field can lead to realisation of the topologically non–trivial states which in finite one dimensional nanowires are manifested by emergence of a pair of zero-energy Majorana bound states. On the other hand, in two dimensional systems the chiral edge states can appear. We investigate novel properties of the bound states in a system of mixed dimensionality, composed of one-dimensional nanowire connected with two-dimensional plaquette. We study this system, assuming either its part or the entire structure to be in topologically non–trivial superconducting state. Our results show delocalisation of the Majorana modes, upon leaking from the nanowire to the plaquette with some tendency towards its corners.
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56
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Machida T, Sun Y, Pyon S, Takeda S, Kohsaka Y, Hanaguri T, Sasagawa T, Tamegai T. Zero-energy vortex bound state in the superconducting topological surface state of Fe(Se,Te). NATURE MATERIALS 2019; 18:811-815. [PMID: 31209388 DOI: 10.1038/s41563-019-0397-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Accepted: 05/08/2019] [Indexed: 06/09/2023]
Abstract
Majorana quasiparticles in condensed matter are important for topological quantum computing1-3, but remain elusive. Vortex cores of topological superconductors may accommodate Majorana quasiparticles that appear as the Majorana bound state (MBS) at zero energy4,5. The iron-based superconductor Fe(Se,Te) possesses a superconducting topological surface state6-9 that was investigated by scanning tunnelling microscopy (STM) studies, which suggest such a zero-energy vortex bound state (ZVBS)10,11. Here we present ultrahigh energy-resolution spectroscopic imaging (SI)-STM to clarify the nature of the vortex bound states in Fe(Se,Te). We found the ZVBS at 0 ± 20 μeV, which constrained its MBS origin, and showed that some vortices host the ZVBS but others do not. We show that the fraction of vortices hosting the ZVBS decreases with increasing magnetic field and that local quenched disorders are not related to the ZVBS. Our observations elucidate the necessary conditions to realize the ZVBS, which paves the way towards controllable Majorana quasiparticles.
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Affiliation(s)
- T Machida
- RIKEN Center for Emergent Matter Science, Wako, Japan.
| | - Y Sun
- Department of Physics and Mathematics, Aoyama Gakuin University, Chuou-ku, Sagamihara, Japan
| | - S Pyon
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Japan
| | - S Takeda
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - Y Kohsaka
- RIKEN Center for Emergent Matter Science, Wako, Japan
| | - T Hanaguri
- RIKEN Center for Emergent Matter Science, Wako, Japan.
| | - T Sasagawa
- Laboratory for Materials and Structures, Tokyo Institute of Technology, Midori-ku, Yokohama, Japan
| | - T Tamegai
- Department of Applied Physics, The University of Tokyo, Bunkyo-ku, Japan
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57
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Jiang HM, Shang JL, Hu LZ. A self-consistent investigation of the topological state in the Ising superconductors. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:295602. [PMID: 30959489 DOI: 10.1088/1361-648x/ab1703] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
By self-consistently solving the Bogoliubov-de Gennes equations, we investigate the superconductivity, the magnetization and the local density-of-state (DOS) of the Ising superconductor. The calculations show that the Ising spin orbital coupling is responsible for the anisotropic behaviors of the Ising superconductor in response to the external magnetic field. In the absence of the magnetic impurities, only opposite spin triplet superconducting (SC) pairing correlations can be induced from the intrinsic on-site singlet SC pairing. The equal spin triplet SC correlations can be induced when a magnetic impurity chain with in-plane spin direction is deposited on the Ising superconductor. The chain could support a pair of Majorana Fermions, which are originated from the induced 1-dimensional equal spin triplet SC pairing correlations. The local DOS for the Majorana Fermion states exhibits an excellent agreement with the experimental observations. The low energy spectrum as a function of the exchange coupling strength forms two hourglass shapes. The waist of the hourglass may serves as a boundary to separate the zero energy crossings of the two lowest energy levels into topologically trivial and non-trivial quantum states. These results not only account for the experimental observations in a realistic way, but also clarify several important questions in the studies of the Ising superconductors.
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58
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Kezilebieke S, Žitko R, Dvorak M, Ojanen T, Liljeroth P. Observation of Coexistence of Yu-Shiba-Rusinov States and Spin-Flip Excitations. NANO LETTERS 2019; 19:4614-4619. [PMID: 31251066 PMCID: PMC6628613 DOI: 10.1021/acs.nanolett.9b01583] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 06/05/2019] [Indexed: 06/09/2023]
Abstract
We investigate the spectral evolution in different metal phthalocyanine molecules on NbSe2 surface using scanning tunnelling microscopy (STM) as a function of the coupling with the substrate. For manganese phthalocyanine (MnPc), we demonstrate a smooth spectral crossover from Yu-Shiba-Rusinov (YSR) bound states to spin-flip excitations. This has not been observed previously and it is in contrast to simple theoretical expectations. We corroborate the experimental findings using numerical renormalization group calculations. Our results provide fundamental new insight on the behavior of atomic scale magnetic/SC hybrid systems, which is important, for example, for engineered topological superconductors and spin logic devices.
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Affiliation(s)
| | - Rok Žitko
- Jožef
Stefan Institute, Jamova 39, SI-1001 Ljubljana, Slovenia
- Faculty
of Mathematics and Physics, University of
Ljubljana, Jadranska
19, SI-1000 Ljubljana, Slovenia
| | - Marc Dvorak
- Department
of Applied Physics, Aalto University School
of Science, 00076 Aalto, Finland
| | - Teemu Ojanen
- Department
of Applied Physics, Aalto University School
of Science, 00076 Aalto, Finland
- Computational
Physics Laboratory, Physics Unit, Faculty of Engineering and Natural
Sciences, Tampere University, P.O. Box 692, FI-33014 Tampere, Finland
| | - Peter Liljeroth
- Department
of Applied Physics, Aalto University School
of Science, 00076 Aalto, Finland
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59
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Atzori M, Sessoli R. The Second Quantum Revolution: Role and Challenges of Molecular Chemistry. J Am Chem Soc 2019; 141:11339-11352. [PMID: 31287678 DOI: 10.1021/jacs.9b00984] [Citation(s) in RCA: 204] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Implementation of modern Quantum Technologies might benefit from the remarkable quantum properties shown by molecular spin systems. In this Perspective, we highlight the role that molecular chemistry can have in the current second quantum revolution, i.e., the use of quantum physics principles to create new quantum technologies, in this specific case by means of molecular components. Herein, we briefly review the current status of the field by identifying the key advances recently made by the molecular chemistry community, such as for example the design of molecular spin qubits with long spin coherence and the realization of multiqubit architectures for quantum gates implementation. With a critical eye to the current state-of-the-art, we also highlight the main challenges needed for the further advancement of the field toward quantum technologies development.
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Affiliation(s)
- Matteo Atzori
- Laboratoire National des Champs Magnétiques Intenses, UPR 3228-CNRS , F-38042 Grenoble , France
| | - Roberta Sessoli
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , I-50019 Sesto Fiorentino , Italy
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60
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Palacio-Morales A, Mascot E, Cocklin S, Kim H, Rachel S, Morr DK, Wiesendanger R. Atomic-scale interface engineering of Majorana edge modes in a 2D magnet-superconductor hybrid system. SCIENCE ADVANCES 2019; 5:eaav6600. [PMID: 31360762 PMCID: PMC6660210 DOI: 10.1126/sciadv.aav6600] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2018] [Accepted: 06/19/2019] [Indexed: 05/14/2023]
Abstract
Topological superconductors are predicted to harbor exotic boundary states-Majorana zero-energy modes-whose non-Abelian braiding statistics present a new paradigm for the realization of topological quantum computing. Using low-temperature scanning tunneling spectroscopy, here, we report on the direct real-space visualization of chiral Majorana edge states in a monolayer topological superconductor, a prototypical magnet-superconductor hybrid system composed of nanoscale Fe islands of monoatomic height on a Re(0001)-O(2 × 1) surface. In particular, we demonstrate that interface engineering by an atomically thin oxide layer is crucial for driving the hybrid system into a topologically nontrivial state as confirmed by theoretical calculations of the topological invariant, the Chern number.
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Affiliation(s)
| | - Eric Mascot
- Department of Physics, University of Illinois at Chicago, 845 W. Taylor St. M/C 273, Chicago, IL, USA
| | - Sagen Cocklin
- Department of Physics, University of Illinois at Chicago, 845 W. Taylor St. M/C 273, Chicago, IL, USA
| | - Howon Kim
- Department of Physics, University of Hamburg, D-20355 Hamburg, Germany
- Corresponding author. (R.W.); (H.K.); (D.K.M.)
| | - Stephan Rachel
- School of Physics, University of Melbourne, Parkville, VIC 3010, Australia
| | - Dirk K. Morr
- Department of Physics, University of Illinois at Chicago, 845 W. Taylor St. M/C 273, Chicago, IL, USA
- Corresponding author. (R.W.); (H.K.); (D.K.M.)
| | - Roland Wiesendanger
- Department of Physics, University of Hamburg, D-20355 Hamburg, Germany
- Corresponding author. (R.W.); (H.K.); (D.K.M.)
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61
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Kobiałka A, Ptok A. Electrostatic formation of the Majorana quasiparticles in the quantum dot-nanoring structure. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2019; 31:185302. [PMID: 30703753 DOI: 10.1088/1361-648x/ab03bf] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Zero-energy Majorana quasiparticles can be induced at the edges of low dimensional systems. Non-Abelian statistics of these states make them valid candidates for the realisation of topological quantum computer. From the practical point of view, it is crucial to obtain a system in which an on demand creation and manipulation of this type of bound states is feasible. In this article, we show such a possibility in a setup comprising a quantum nanoring in which we specify a quantum dot region via electrostatic means. The presence of quantum dot can lead to the emergence of Andreev and Majorana bound states in the investigated system. We study the differences between those two types of bound states and the possibility of their manipulation. Moreover, the exact calculation method for spectral function has been proposed, which can be used to study the influence of bound states on the band structure of the proposed system. Using this method, it can be shown that the Majorana bound states, induced at the edge of the system, present themselves as a dispersionless zero-energy flat-band.
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Affiliation(s)
- Aksel Kobiałka
- Institute of Physics, Maria Curie-Skłodowska University, Plac Marii Skłodowskiej-Curie 1, PL-20031 Lublin, Poland
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62
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Blick RH, Graener H, Mews A, Weller H, Wiesendanger R, Parak WJ. Nanoscience and Nanotechnology at the Centennial of Universität Hamburg. ACS NANO 2019; 13:1-3. [PMID: 30785723 DOI: 10.1021/acsnano.9b00223] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Affiliation(s)
- Robert H Blick
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
| | - Heinrich Graener
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
| | - Alf Mews
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
| | - Horst Weller
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
| | - Roland Wiesendanger
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
| | - Wolfgang J Parak
- Faculty of Mathematics, Informatics and Natural Sciences , Universität Hamburg , 20355 Hamburg , Germany
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63
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Malavolti L, Briganti M, Hänze M, Serrano G, Cimatti I, McMurtrie G, Otero E, Ohresser P, Totti F, Mannini M, Sessoli R, Loth S. Tunable Spin-Superconductor Coupling of Spin 1/2 Vanadyl Phthalocyanine Molecules. NANO LETTERS 2018; 18:7955-7961. [PMID: 30452271 DOI: 10.1021/acs.nanolett.8b03921] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Atomic-scale magnetic moments in contact with superconductors host rich physics based on the emergence of Yu-Shiba-Rusinov (YSR) magnetic bound states within the superconducting condensate. Here, we focus on a magnetic bound state induced into Pb nanoislands by individual vanadyl phthalocyanine (VOPc) molecules deposited on the Pb surface. The VOPc molecule is characterized by a spin magnitude of 1/2 arising from a well-isolated singly occupied d xy-orbital and is a promising candidate for a molecular spin qubit with long coherence times. X-ray magnetic circular dichroism (XMCD) measurements show that the molecular spin remains unperturbed even for molecules directly deposited on the Pb surface. Scanning tunneling spectroscopy and density functional theory (DFT) calculations identify two adsorption geometries for this "asymmetric" molecule (i.e., absence of a horizontal symmetry plane): (a) oxygen pointing toward the vacuum with the Pc laying on the Pb, showing negligible spin-superconductor interaction, and (b) oxygen pointing toward the Pb, presenting an efficient interaction with the Pb and promoting a Yu-Shiba-Rusinov bound state. Additionally, we find that in the first case a YSR state can be induced smoothly by exerting mechanical force on the molecules with the scanning tunneling microscope (STM) tip. This allows the interaction strength to be tuned continuously from an isolated molecular spin case, through the quantum critical point (where the bound state energy is zero) and beyond. DFT indicates that a gradual bending of the VO bond relative to the Pc ligand plane promoted by the STM tip can modify the interaction in a continuously tunable manner. The ability to induce a tunable YSR state in the superconductor suggests the possibility of introducing coupled spins on superconductors with switchable interaction.
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Affiliation(s)
- Luigi Malavolti
- Institute for Functional Matter and Quantum Technologies , University of Stuttgart , 70569 Stuttgart , Germany
- Max Planck Institute for the Structure and Dynamics of Matter , 22761 Hamburg , Germany
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Matteo Briganti
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Max Hänze
- Institute for Functional Matter and Quantum Technologies , University of Stuttgart , 70569 Stuttgart , Germany
- Max Planck Institute for the Structure and Dynamics of Matter , 22761 Hamburg , Germany
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Giulia Serrano
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Irene Cimatti
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Gregory McMurtrie
- Institute for Functional Matter and Quantum Technologies , University of Stuttgart , 70569 Stuttgart , Germany
- Max Planck Institute for the Structure and Dynamics of Matter , 22761 Hamburg , Germany
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
| | - Edwige Otero
- Synchrotron SOLEIL , 4891192 Gif-sur-Yvette , France
| | | | - Federico Totti
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Matteo Mannini
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Roberta Sessoli
- Dipartimento di Chimica "Ugo Schiff" & INSTM RU , Università degli Studi di Firenze , Via della Lastruccia 3-13 , 150019 Sesto Fiorentino (Firenze) , Italy
| | - Sebastian Loth
- Institute for Functional Matter and Quantum Technologies , University of Stuttgart , 70569 Stuttgart , Germany
- Max Planck Institute for the Structure and Dynamics of Matter , 22761 Hamburg , Germany
- Max Planck Institute for Solid State Research , 70569 Stuttgart , Germany
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64
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Górski G, Barański J, Weymann I, Domański T. Interplay between correlations and Majorana mode in proximitized quantum dot. Sci Rep 2018; 8:15717. [PMID: 30356206 PMCID: PMC6200813 DOI: 10.1038/s41598-018-33529-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Accepted: 09/28/2018] [Indexed: 11/09/2022] Open
Abstract
We study the low energy spectrum and transport properties of a correlated quantum dot coupled between normal and superconducting reservoirs and additionally hybridized with a topological superconducting nanowire, hosting the Majorana end-modes. In this setup the Majorana quasiparticle leaking into the quantum dot can be confronted simultaneously with the on-dot pairing and correlations. We study this interplay, focusing on the quantum phase transition from the spinless (BCS-type) to the spinful (singly occupied) configuration, where the subgap Kondo effect may arise. Using the selfconsistent perturbative treatment for correlations and the unbiased numerical renormalization group calculations we find that the Majorana mode has either constructive or destructive effect on the low-energy transport behavior of the quantum dot, depending on its spin. This spin-selective influence could be verified by means of the polarized STM spectroscopy.
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Affiliation(s)
- G Górski
- Faculty of Mathematics and Natural Sciences, University of Rzeszów, 35-310, Rzeszów, Poland
| | - J Barański
- Polish Air Force Academy, ul. Dywizjonu 303, 08-521, Dęblin, Poland
| | - I Weymann
- Faculty of Physics, A. Mickiewicz University, 61-614, Poznań, Poland
| | - T Domański
- Institute of Physics, M. Curie-Skłodowska University, 20-031, Lublin, Poland.
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65
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Engineering the spin couplings in atomically crafted spin chains on an elemental superconductor. Nat Commun 2018; 9:3253. [PMID: 30108221 PMCID: PMC6092363 DOI: 10.1038/s41467-018-05701-8] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 07/18/2018] [Indexed: 11/09/2022] Open
Abstract
Magnetic atoms on a superconductor give rise to Yu-Shiba-Rusinov (YSR) states within the superconducting energy gap. A spin chain of magnetic adatoms on an s-wave superconductor may lead to topological superconductivity accompanied by the emergence of Majorana modes at the chain ends. For their usage in quantum computation, it is a prerequisite to artificially assemble the chains and control the exchange couplings between the spins in the chain and in the substrate. Here, using a scanning tunneling microscope tip, we demonstrate engineering of the energy levels of the YSR states by placing interstitial Fe atoms in close proximity to adsorbed Fe atoms on an oxidized Ta surface. Based on this prototype platform, we show that the interaction within a long chain can be strengthened by linking the adsorbed Fe atoms with the interstitial ones. Our work adds an important step towards the controlled design and manipulation of Majorana end states. Magnetic atomic chains assembled on the surface of superconductors are a potential platform for engineering topological superconducting phases. Here the authors step towards this by manipulating magnetic atoms at interstitial sites to tune interatomic interactions and control the Yu-Shiba-Rusinov states that form.
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