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We proposed a formula for the $Z_2$ invariant for topological insulators, which remains valid without translational invariance. Our formula is a local expression, in the sense that the contributions mainly come from quantities near a point.…

Mesoscale and Nanoscale Physics · Physics 2019-11-07 Zhi Li , Roger S. K. Mong

We formulate the lattice version of the three-dimensional SU(2) Landau level problem with time reversal invariance. By taking a Landau-type gauge, the system is reduced into the one-dimensional SU(2) Harper equation characterized by a…

Strongly Correlated Electrons · Physics 2015-06-04 Yi Li

The relation between bulk topological invariants and experimentally observable physical quantities is a fundamental property of topological insulators and superconductors. In the case of chiral symmetric systems in odd spatial dimensions…

Mesoscale and Nanoscale Physics · Physics 2013-02-20 Ken Shiozaki , Satoshi Fujimoto

We present two modules that expand functionalities of the all-electron full-potential density functional theory package WIEN2k for computation of the Chern and $Z_2$ topological invariants. Characterization of topological properties relies…

Computational Physics · Physics 2023-08-28 Andres F. Gomez-Bastidas , Oleg Rubel

The role of disorder in the field of three-dimensional time reversal invariant topological insulators has become an active field of research recently. However, the computation of Z2 invariants for large, disordered systems still poses a…

Mesoscale and Nanoscale Physics · Physics 2014-04-16 Björn Sbierski , Piet W. Brouwer

We show that there exist two dimensional (2D) time reversal invariant fractionalized insulators with the property that both their boundary with the vacuum and their boundary with a topological insulator can be fully gapped without breaking…

Strongly Correlated Electrons · Physics 2014-04-21 Chenjie Wang , Michael Levin

We introduce a new expression for the Z2 topological invariant of band insulators using non- Abelian Berry's connection. Our expression can identify the topological nature of a general band insulator without any of the gauge fixing problems…

Materials Science · Physics 2015-03-17 Rui Yu , Xiao Liang Qi , Andrei Bernevig , Zhong Fang , Xi Dai

We study translationally-invariant insulators with inversion symmetry that fall outside the established classification of topological insulators. These insulators are not required to have gapless boundary modes in the energy spectrum.…

Mesoscale and Nanoscale Physics · Physics 2013-05-29 Taylor L. Hughes , Emil Prodan , B. Andrei Bernevig

This paper is a survey of the $\mathbb{Z}_2$-valued invariant of topological insulators used in condensed matter physics. The $\mathbb{Z}$-valued topological invariant, which was originally called the TKNN invariant in physics, has now been…

Mathematical Physics · Physics 2016-12-28 Ralph M. Kaufmann , Dan Li , Birgit Wehefritz-Kaufmann

We revisit the question of whether a two-dimensional topological insulator may arise in a commensurate N\'eel antiferromagnet, where staggered magnetization breaks both the elementary translation and time reversal, but retains their product…

Strongly Correlated Electrons · Physics 2016-04-07 Frédéric Bègue , Pierre Pujol , Revaz Ramazashvili

We show that the Z$_2$ invariant, which classifies the topological properties of time reversal invariant insulators, has deep relationship with the global anomaly. Although the second Chern number is the basic topological invariant…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 T. Fukui , T. Fujiwara , Y. Hatsugai

We show that the bulk winding number characterizing one-dimensional topological insulators with chiral symmetry can be detected from the displacement of a single particle, observed via losses. Losses represent the effect of repeated weak…

Mesoscale and Nanoscale Physics · Physics 2017-05-17 Tibor Rakovszky , Janos K. Asboth , Andrea Alberti

We investigate the possibility of constructing exponentially localized composite Wannier bases, or equivalently smooth periodic Bloch frames, for 3-dimensional time-reversal symmetric topological insulators, both of bosonic and of fermionic…

Mathematical Physics · Physics 2017-11-16 Horia D. Cornean , Domenico Monaco

We define topological invariants in terms of the ground states wave functions on a torus. This approach leads to precisely defined formulas for the Hall conductance in four dimensions and the topological magneto-electric $\theta$ term in…

Strongly Correlated Electrons · Physics 2014-01-28 Zhong Wang , Shou-Cheng Zhang

Topological insulators are a broad class of unconventional materials that are insulating in the interior but conduct along the edges. This edge transport is topologically protected and dissipationless. Until recently, all existing…

We introduce the topologically twisted index for four-dimensional $\mathcal N=1$ gauge theories quantized on ${\rm AdS}_2 \times S^1$. We compute the index by applying supersymmetric localization to partition functions of vector and chiral…

High Energy Physics - Theory · Physics 2023-07-24 Daniele Iannotti , Antonio Pittelli

We propose a definition of a ${\mathbb Z}_2$ topological invariant for magnon spin Hall systems which are the bosonic analog of two-dimensional topological insulators in class AII. The existence of "Kramers pairs" in these systems is…

Mesoscale and Nanoscale Physics · Physics 2020-10-07 Hiroki Kondo , Yutaka Akagi , Hosho Katsura

Topological Insulators (TIs) are unique materials where insulating bulk hosts linearly dispersing surface states protected by the Time-Reversal Symmetry (TRS). These states lead to dissipationless current flow, which makes this class of…

Materials Science · Physics 2022-05-19 Ankita Phutela , Preeti Bhumla , Manjari Jain , Saswata Bhattacharya

This paper reviews several analytic tools for the field of topological insulators, developed with the aid of non-commutative calculus and geometry. The set of tools includes bulk topological invariants defined directly in the thermodynamic…

Statistical Mechanics · Physics 2010-06-22 Emil Prodan

We propose a new method to numerically compute the $\mathbb{Z}_2$ indices for disordered topological insulators in Kitaev's periodic table. All of the $\mathbb{Z}_2$ indices are known to be derived from the index formulae which are…

Mesoscale and Nanoscale Physics · Physics 2017-12-13 Yutaka Akagi , Hosho Katsura , Tohru Koma