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Topological insulators are insulating in the bulk but feature conducting states on their surfaces. Standard methods for probing their topological properties largely involve probing the surface, even though topological invariants are defined…

Topological classification of quantum solids often (if not always) groups all trivial atomic or normal insulators (NIs) into the same featureless family. As we argue here, this is not necessarily the case always. In particular, when the…

Mesoscale and Nanoscale Physics · Physics 2023-07-26 Sanjib Kumar Das , Sourav Manna , Bitan Roy

Examples of non-hermitian quantum systems admitting topological insulator phase are presented in one, two and three space dimensions. All of these non-hermitian Hamiltonians have entirely real bulk eigenvalues and unitarity is maintained…

Quantum Physics · Physics 2012-03-19 Pijush K. Ghosh

We present an approach for the calculation of the $\mathbb{Z}_2$ topological invariant in non-crystalline two-dimensional quantum spin Hall insulators. While topological invariants were originally mathematically introduced for crystalline…

Mesoscale and Nanoscale Physics · Physics 2023-02-28 Roberta Favata , Antimo Marrazzo

An exhaustive classification scheme of topological insulators and superconductors is presented. The key property of topological insulators (superconductors) is the appearance of gapless degrees of freedom at the interface/boundary between a…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 Andreas P. Schnyder , Shinsei Ryu , Akira Furusaki , Andreas W. W. Ludwig

Topological insulators are new states of quantum matter which can not be adiabatically connected to conventional insulators and semiconductors. They are characterized by a full insulating gap in the bulk and gapless edge or surface states…

Mesoscale and Nanoscale Physics · Physics 2011-11-09 Xiao-Liang Qi , Shou-Cheng Zhang

We show that compositions of time-reversal and spatial symmetries, also known as the magnetic-space-group symmetries, protect topological invariants as well as surface states that are distinct from those of all preceding topological states.…

Mesoscale and Nanoscale Physics · Physics 2022-07-13 Bingrui Peng , Yi Jiang , Zhong Fang , Hongming Weng , Chen Fang

We investigate an extension of ideas of Atiyah-Patodi-Singer (APS) to a noncommutative geometry setting framed in terms of Kasparov modules. We use a mapping cone construction to relate odd index pairings to even index pairings with APS…

K-Theory and Homology · Mathematics 2008-02-04 A. L. Carey , J. Phillips , A. Rennie

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near-field of an atom-chip, which effectively mimics the effects…

In this work, a complete homotopic interpretation on the periodic table of topological insulators and superconductors has been derived by establishing the loop sequence of the corresponding classifying spaces. In our approach, each…

Mathematical Physics · Physics 2013-11-13 Chunbo Zhao

In this paper topological $K$-group calculations for fiber bundles with structure group $SO(3)$ over tori are carried out to explain why topological insulators have special conducting points on their surface but are bulk insulators. It is…

Strongly Correlated Electrons · Physics 2026-03-02 Koushik Ray , Siddhartha Sen

Chiral surface states in topological insulators are robust against interactions, non-magnetic disorder and localization, yet topology does not yield protection in transport. This work presents a theory of interacting topological insulators…

Mesoscale and Nanoscale Physics · Physics 2015-03-19 Dimitrie Culcer

Non-commutative analysis tools have successfully been applied to the integer quantum Hall effect, in particular for a proof of the stability of the Hall conductance in an Anderson localization regime and of the bulk-boundary correspondence.…

Mathematical Physics · Physics 2018-05-29 Giuseppe De Nittis , Hermann Schulz-Baldes

In this work we consider whether nonsymmorphic symmetries such as a glide plane can protect the existence of topological crystalline insulators and superconductors in three dimensions. In analogy to time-reversal symmetric insulators, we…

Strongly Correlated Electrons · Physics 2015-11-11 Daniel Varjas , Fernando de Juan , Yuan-Ming Lu

A definition of topological phases of density matrices is presented. The topological invariants in case of both noninteracting and interacting systems are extended to nonzero temperatures. Influence of electron interactions on topological…

Strongly Correlated Electrons · Physics 2015-09-03 Damian Zdulski , Krzysztof Byczuk

We define and study the index map for families of $G$-transversally elliptic operators and introduce the multiplicity for a given irreducible representation as a virtual bundle over the base of the fibration. We then prove the usual…

K-Theory and Homology · Mathematics 2019-04-24 Alexandre Baldare

Topological insulators are a new class of materials which have gapped spectra in the bulk, but are accompanied by topologically protected gapless excitations at the surface (edge) of the system. These phenomena have a close relationship…

Mesoscale and Nanoscale Physics · Physics 2015-11-30 Taro Kimura

We describe the index pairing between an odd K-theory class and an odd unbounded Kasparov module by a pair of quasi-projections, supported on a submodule obtained from a finite spectral truncation. We achieve this by pairing the K-theory…

K-Theory and Homology · Mathematics 2026-04-01 Yuezhao Li , Bram Mesland

Electronic topological insulators are one of the breakthroughs of the 21st century condensed matter physics. So far, the search for a light counterpart of an electronic topological insulator has remained elusive. This is due to the…

Mesoscale and Nanoscale Physics · Physics 2016-02-05 Mario G. Silveirinha

The possibility of realizing topological insulators by spontaneous formation of electronic superstructure is theoretically investigated in a minimal two-orbital model including both the spin-orbit coupling and electron correlations on a…

Strongly Correlated Electrons · Physics 2016-06-21 Yusuke Sugita , Yukitoshi Motome