Topological Crystalline Insulators: Current Progress and Prospects

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (1 December 2016) | Viewed by 32219

Special Issue Editor


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Guest Editor
School of Physics and Astronomy, University of Leeds, Leeds, UK
Interests: exotic superconductors; Dirac, Weyl, and Majorana fermions in topological materials; electronic and transport properties; magnetoelectric effects; phase transition; growth of single crystals, thin films, and crystalline nanostructures of topological materials; macroscopic quantum phenomena; surface and interface; nanofabrications

Special Issue Information

Dear Colleagues,

The discovery of topological insulators with time-reversal symmetry has reignited interest in symmetry and topology of band structures in solid-state physics and chemistry. Interestingly, it has been theoretically demonstrated that different classes of symmetry in materials can protect relevant topological phases of matter. For example, topological superconducting phases that can harbor Majorana fermions can be protected by particle-hole symmetry.

Crystalline systems can adopt a huge variety of symmetries, including reflection (mirror) and rotation operations in point group symmetry, and symmorphic/nonsymmorphic operations in space group symmetry. Therefore, crystals have enormous potential for the existence of novel topological phases.

Topological crystalline insulators (TCIs) that exhibit these rich topological phases of matter have been attracting much interest in material research and their realization in real materials is interesting and challenging. Hence, it is worth summarizing current progress in the study of topological crystalline insulators and discussing what can be the milestones and prospects of these materials. By organizing this Special Issue, we aim to contribute to the topological community and those who will start the study in this field.

If you, as an investigator in this field, approve of our intention, we are happy to invite you to contribute to this Special Issue. Under “keywords” you can find various types of work related to the study of TCIs that would qualify as topics. Please note that this list is not inclusive.

Dr. Satoshi Sasaki
Guest Editor

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Keywords

  • Growth of bulk crystals, thin films, and crystalline nanostructures
  • Material classifications with respect to symmetry-protected topological phases of matter in different dimensions
  • Electronic band structures, electronic properties, transport properties
  • Surface and interface
  • Superconductivities
  • Dirac fermions and/or Majorana fermions
  • Crystal defects and/or impurity effects

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Published Papers (5 papers)

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Research

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1553 KiB  
Article
Topology and Holonomy in Discrete-time Quantum Walks
by Graciana Puentes
Crystals 2017, 7(5), 122; https://doi.org/10.3390/cryst7050122 - 28 Apr 2017
Cited by 5 | Viewed by 5206
Abstract
We present a research article which formulates the milestones for the understanding and characterization of holonomy and topology of a discrete-time quantum walk architecture, consisting of a unitary step given by a sequence of two non-commuting rotations in parameter space. Unlike other similar [...] Read more.
We present a research article which formulates the milestones for the understanding and characterization of holonomy and topology of a discrete-time quantum walk architecture, consisting of a unitary step given by a sequence of two non-commuting rotations in parameter space. Unlike other similar systems recently studied in detail in the literature, this system does not present continous 1D topological boundaries, it only presents a discrete number of Dirac points where the quasi-energy gap closes. At these discrete points, the topological winding number is not defined. Therefore, such discrete points represent topological boundaries of dimension zero, and they endow the system with a non-trivial topology. We illustrate the non-trivial character of the system by calculating the Zak phase. We discuss the prospects of this system, we propose a suitable experimental scheme to implement these ideas, and we present preliminary experimental data. Full article
(This article belongs to the Special Issue Topological Crystalline Insulators: Current Progress and Prospects)
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985 KiB  
Article
Unexpected Au Alloying in Tailoring In-Doped SnTe Nanostructures with Gold Nanoparticles
by Samuel Atherton, Benjamin Steele and Satoshi Sasaki
Crystals 2017, 7(3), 78; https://doi.org/10.3390/cryst7030078 - 6 Mar 2017
Cited by 4 | Viewed by 4463
Abstract
Materials with strong spin-orbit interaction and superconductivity are candidates for topological superconductors that may host Majorana fermions (MFs) at the edges/surfaces/vortex cores. Bulk-superconducting carrier-doped topological crystalline insulator, indium-doped tin telluride (In-SnTe) is one of the promising materials. Robust superconductivity of In-SnTe nanostructures has [...] Read more.
Materials with strong spin-orbit interaction and superconductivity are candidates for topological superconductors that may host Majorana fermions (MFs) at the edges/surfaces/vortex cores. Bulk-superconducting carrier-doped topological crystalline insulator, indium-doped tin telluride (In-SnTe) is one of the promising materials. Robust superconductivity of In-SnTe nanostructures has been demonstrated recently. Intriguingly, not only 3-dimensional (3D) nanostructures but also ultra-thin quasi-2D and quasi-1D systems can be grown by the vapor transport method. In particular, nanostructures with a controlled dimension will give us a chance to understand the dimensionality and the quantum confinement effects on the superconductivity of the In-SnTe and may help us work on braiding MFs in various dimensional systems for future topological quantum computation technology. With this in mind, we employed gold nanoparticles (GNPs) with well-identified sizes to tailor In-SnTe nanostructures grown by vapor transport. However, we could not see clear evidence that the presence of the GNPs is necessary or sufficient to control the size of the nanostructures. Nevertheless, it should be noted that a weak correlation between the diameter of GNPs and the dimensions of the smallest nanostructures has been found so far. To our surprise, the ones grown under the vapor–liquid–solid mechanism, with the use of the GNPs, contained gold that is widely and inhomogeneously distributed over the whole body. Full article
(This article belongs to the Special Issue Topological Crystalline Insulators: Current Progress and Prospects)
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3813 KiB  
Article
Anisotropic Magnetic Responses of Topological Crystalline Superconductors
by Yuansen Xiong, Ai Yamakage, Shingo Kobayashi, Masatoshi Sato and Yukio Tanaka
Crystals 2017, 7(2), 58; https://doi.org/10.3390/cryst7020058 - 17 Feb 2017
Cited by 20 | Viewed by 5131
Abstract
Majorana Kramers pairs emerged on surfaces of time-reversal-invariant topological crystalline superconductors show the Ising anisotropy to an applied magnetic field. We clarify that crystalline symmetry uniquely determines the direction of the Majorana Ising spin for given irreduciblerepresentationsofpairpotential,derivingconstraintstotopologicalinvariants. In addition, necessary conditions for nontrivial [...] Read more.
Majorana Kramers pairs emerged on surfaces of time-reversal-invariant topological crystalline superconductors show the Ising anisotropy to an applied magnetic field. We clarify that crystalline symmetry uniquely determines the direction of the Majorana Ising spin for given irreduciblerepresentationsofpairpotential,derivingconstraintstotopologicalinvariants. In addition, necessary conditions for nontrivial topological invariants protected by the n-fold rotational symmetry are shown. Full article
(This article belongs to the Special Issue Topological Crystalline Insulators: Current Progress and Prospects)
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3306 KiB  
Article
Indium Substitution Effect on the Topological Crystalline Insulator Family (Pb1−xSnx)1−yInyTe: Topological and Superconducting Properties
by Ruidan Zhong, John Schneeloch, Qiang Li, Wei Ku, John Tranquada and Genda Gu
Crystals 2017, 7(2), 55; https://doi.org/10.3390/cryst7020055 - 16 Feb 2017
Cited by 21 | Viewed by 8092
Abstract
Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx)1−yIn [...] Read more.
Topological crystalline insulators (TCIs) have been of great interest in the area of condensed matter physics. We investigated the effect of indium substitution on the crystal structure and transport properties in the TCI system (Pb1−xSnx)1−yInyTe. For samples with a tin concentration x 50 % , the low-temperature resisitivities show a dramatic variation as a function of indium concentration: with up to ∼2% indium doping, the samples show weak-metallic behavior similar to their parent compounds; with ∼6% indium doping, samples have true bulk-insulating resistivity and present evidence for nontrivial topological surface states; with higher indium doping levels, superconductivity was observed, with a transition temperature, T c , positively correlated to the indium concentration and reaching as high as 4.7 K. We address this issue from the view of bulk electronic structure modified by the indium-induced impurity level that pins the Fermi level. The current work summarizes the indium substitution effect on (Pb,Sn)Te, and discusses the topological and superconducting aspects, which can be provide guidance for future studies on this and related systems. Full article
(This article belongs to the Special Issue Topological Crystalline Insulators: Current Progress and Prospects)
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Review

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2347 KiB  
Review
Dirac Landau Level Spectroscopy in Pb1−xSnxSe and Pb1−xSnxTe across the Topological Phase Transition: A Review
by Thanyanan Phuphachong, Badih A. Assaf, Valentine V. Volobuev, Günther Bauer, Gunther Springholz, Louis-Anne De Vaulchier and Yves Guldner
Crystals 2017, 7(1), 29; https://doi.org/10.3390/cryst7010029 - 20 Jan 2017
Cited by 19 | Viewed by 8525
Abstract
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSn [...] Read more.
Topological crystalline insulators (TCIs) are topological materials that have Dirac surface states occurring at crystalline symmetric points in the Brillouin zone. This topological state has been experimentally shown to occur in the lead–tin salts Pb1−xSnxSe and Pb1−xSnxTe. More recent works also took interest in studying the topological phase transition from trivial to non-trivial topology that occurs in such materials as a function of increasing Sn content. A peculiar property of these materials is the fact that their bulk bands disperse following a massive Dirac dispersion that is linear at low energies above the energy gap. This makes Pb1−xSnxSe and Pb1−xSnxTe ideal platforms to simultaneously study 3D and 2D Dirac physics. In this review, we will go over infrared magneto-optical studies of the Landau level dispersion of Pb1−xSnxSe and Pb1−xSnxTe for both the bulk and surface bands and summarize work that has been done on this matter. We will review recent work on probing the topological phase transition in TCI. We will finally present our views on prospects and open questions that have yet to be addressed in magneto-optical spectroscopy studies on Pb1-xSnxSe and Pb1−xSnxTe. Full article
(This article belongs to the Special Issue Topological Crystalline Insulators: Current Progress and Prospects)
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