Special Issue "Majorana Fermions and Topological Materials Science"

A special issue of Condensed Matter (ISSN 2410-3896).

Deadline for manuscript submissions: closed (15 January 2019)

Special Issue Editors

Guest Editor
Prof. Antonio Bianconi

Rome International Center for Materials Science Superstripes (RICMASS), Via dei Sabelli 119A, 00185 Roma, Italy
Website | E-Mail
Phone: +39 3388438281
Fax: +39 06 4957697
Interests: Experimental methods: synchrotron radiation research, XANES spectroscopy, many body effects in XANES, scanning micro x-ray diffraction; Materials: transition metal oxides, high Tc superconductors, metallo-proteins, biological systems; Quantum phenomena in complex matter: lattice and electronic complexity, polymorphism, valence fluctuation, multi-band Hubbard models, superstripes, nanoscale electronic phase separation, protein fluctuations, effective charge and coordination in active sites of metalloproteins, origin of life
Guest Editor
Prof. Yoshiteru Maeno

Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
Website | E-Mail
Interests: thermal convection and chaos in helium superfluids, magnetism and superconductivity in Chevrel-phase and heavy-fermion compounds, substitution effects in cuprate high-temperature superconductors, spin frustrations in spin ice, unconventional superconductivity and metal-insulator transitions, non-equilibrium steady states (NESS) of strongly correlated electron systems, topological quantum phenomena

Special Issue Information

Dear Colleagues,

Following the initial outbreak of research triggered by the discovery of topological insulators just a decade ago, the concept of topology continues to drive the expansion of the frontiers in modern condensed matter physics.

Target topological materials of current interests include various forms of superconductivity, novel semimetals, and correlated magnets. Efforts to firmly establish Majorana particles in condensed matter also extends to these variety of topological materials. The aim of this special issue is to bring together active scientists in this field to discuss recent advances in topological materials science, thereby to identify the most important questions and find directions to answer them.

Prof. Antonio Bianconi
Prof. Yoshiteru Maeno
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Condensed Matter is an international peer-reviewed open access quarterly journal published by MDPI.

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Keywords

  • Majorana fermions
  • Topological superconductivity of bulk topological superconductors
  • Topologocal superconductivity in heterostructures and junctions
  • Topological condensates (BEC-BCS crossover, Cold atoms, Helium)
  • Dirac and Weyl materials
  • Correlations and topology

Published Papers (5 papers)

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Research

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Open AccessArticle Engineering Topological Nodal Line Semimetals in Rashba Spin-Orbit Coupled Atomic Chains
Condens. Matter 2019, 4(1), 25; https://doi.org/10.3390/condmat4010025 (registering DOI)
Received: 30 January 2019 / Revised: 13 February 2019 / Accepted: 15 February 2019 / Published: 16 February 2019
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Abstract
In this paper, we study an atomic chain in the presence of modulated charge potential and modulated Rashba spin-orbit coupling (RSOC) of equal periods. We show that for commensurate periodicities, λ=4n with integer n, the three-dimensional synthetic space obtained [...] Read more.
In this paper, we study an atomic chain in the presence of modulated charge potential and modulated Rashba spin-orbit coupling (RSOC) of equal periods. We show that for commensurate periodicities, λ = 4 n with integer n, the three-dimensional synthetic space obtained by sliding the two phases of the charge potential and RSOC features a topological nodal-line semimetal protected by an anti-unitary particle-hole symmetry. The location and shape of the nodal lines strongly depend on the relative amplitude between the charge potential and RSOC. Full article
(This article belongs to the Special Issue Majorana Fermions and Topological Materials Science)
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Open AccessArticle Proximity-Induced Superconducting States of Magnetically Doped 3D Topological Insulators with High Bulk Insulation
Condens. Matter 2019, 4(1), 9; https://doi.org/10.3390/condmat4010009
Received: 25 November 2018 / Revised: 22 December 2018 / Accepted: 7 January 2019 / Published: 12 January 2019
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Abstract
We studied magnetized topological insulator/superconductor junctions with the expectation of unconventional superconductive states holding Majorana fermions induced by superconductive proximity effects on the surface states of magnetized topological insulators (TIs), attached by conventional superconductors. We introduced Fe-doped BiSbTe2Se as an ideal [...] Read more.
We studied magnetized topological insulator/superconductor junctions with the expectation of unconventional superconductive states holding Majorana fermions induced by superconductive proximity effects on the surface states of magnetized topological insulators (TIs), attached by conventional superconductors. We introduced Fe-doped BiSbTe2Se as an ideal magnetic TI and used the developed junction fabrication process to access the proximity-induced surface superconducting states. The bulk single crystals of the Fe-doped TI showed excellent bulk-insulating properties and ferromagnetism simultaneously at a low temperature. Meanwhile, the fabricated junctions also showed an insulating behavior above 100 K, as well as metallic conduction at a low temperature, which reflects bulk carrier freezing. In addition, we observed a proximity-induced gap structure in the conductance spectra. These results indicate that the junctions using the established materials and process are preferable to observe unconventional superconducting states which are induced via the surface channels of the magnetized TI. We believe that the developed process can be applied for the fabrication of complicated junctions and suites for braiding operations. Full article
(This article belongs to the Special Issue Majorana Fermions and Topological Materials Science)
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Open AccessArticle Improved Single-Crystal Growth of Sr2RuO4
Condens. Matter 2019, 4(1), 6; https://doi.org/10.3390/condmat4010006
Received: 26 November 2018 / Revised: 24 December 2018 / Accepted: 2 January 2019 / Published: 7 January 2019
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Abstract
High-quality single crystals are essentially needed for the investigation of the novel bulk properties of unconventional superconductors. The availability of such crystals grown by the floating-zone method has helped to unveil the unconventional superconductivity of the layered perovskite Sr2RuO4, [...] Read more.
High-quality single crystals are essentially needed for the investigation of the novel bulk properties of unconventional superconductors. The availability of such crystals grown by the floating-zone method has helped to unveil the unconventional superconductivity of the layered perovskite Sr2RuO4, which is considered as a strong candidate of a topological spin-triplet superconductor. Yet, recent progress of investigations urges further efforts to obtain ultimately high-quality crystalline samples. In this paper, we focus on the method of preparation of feed rods for the floating-zone melting and report on the improvements of the crystal growth. We present details of the improved methods used to obtain crystals with superconducting transition temperatures Tc that are consistently as high as 1.4 K, as well as the properties of these crystals. Full article
(This article belongs to the Special Issue Majorana Fermions and Topological Materials Science)
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Open AccessArticle Electric Polarization in Magnetic Topological Nodal Semimetal Thin Films
Condens. Matter 2018, 3(4), 43; https://doi.org/10.3390/condmat3040043
Received: 1 November 2018 / Revised: 23 November 2018 / Accepted: 28 November 2018 / Published: 30 November 2018
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Abstract
We theoretically study the electric polarization in magnetic topological nodal semimetal thin films. In magnetically doped topological insulators, topological nodal semimetal phases emerge once the exchange coupling overcomes the band gap. Changing the magnetization direction, nodal structure is modulated and the system becomes [...] Read more.
We theoretically study the electric polarization in magnetic topological nodal semimetal thin films. In magnetically doped topological insulators, topological nodal semimetal phases emerge once the exchange coupling overcomes the band gap. Changing the magnetization direction, nodal structure is modulated and the system becomes topological nodal point or line semimetals. We find that nodal line semimetals are characterized by non-linear electric polarization, which is not observed in nodal point semimetals. The non-linear response originates from the existence of the surface states. Screening effect is self consistently included within a mean field approximation and the non-linear electric polarization is observed even in the presence of screening effect. Full article
(This article belongs to the Special Issue Majorana Fermions and Topological Materials Science)
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Review

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Open AccessReview Nematic Superconductivity in Doped Bi2Se3 Topological Superconductors
Condens. Matter 2019, 4(1), 2; https://doi.org/10.3390/condmat4010002
Received: 27 November 2018 / Revised: 13 December 2018 / Accepted: 19 December 2018 / Published: 20 December 2018
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Abstract
Nematic superconductivity is a novel class of superconductivity characterized by spontaneous rotational-symmetry breaking in the superconducting gap amplitude and/or Cooper-pair spins with respect to the underlying lattice symmetry. Doped Bi2Se3 superconductors, such as CuxBi2Se3, [...] Read more.
Nematic superconductivity is a novel class of superconductivity characterized by spontaneous rotational-symmetry breaking in the superconducting gap amplitude and/or Cooper-pair spins with respect to the underlying lattice symmetry. Doped Bi 2 Se 3 superconductors, such as Cu x Bi 2 Se 3 , Sr x Bi 2 Se 3 , and Nb x Bi 2 Se 3 , are considered as candidates for nematic superconductors, in addition to the anticipated topological superconductivity. Recently, various bulk probes, such as nuclear magnetic resonance, specific heat, magnetotransport, magnetic torque, and magnetization, have consistently revealed two-fold symmetric behavior in their in-plane magnetic-field-direction dependence, although the underlying crystal lattice possesses three-fold rotational symmetry. More recently, nematic superconductivity was directly visualized using scanning tunneling microscopy and spectroscopy. In this short review, we summarize the current research on the nematic behavior in superconducting doped Bi 2 Se 3 systems and discuss issues and perspectives. Full article
(This article belongs to the Special Issue Majorana Fermions and Topological Materials Science)
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