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Periodic Hamiltonians on a three-dimensional (3-D) lattice with a spectral gap not only on the bulk but also on two edges at the common Fermi level are considered. By using K-theory applied for the quarter-plane Toeplitz extension, two…

Mathematical Physics · Physics 2018-10-18 Shin Hayashi

Two-dimensional (2D) massless Dirac electrons appear on a surface of three-dimensional topological insulators. The conductivity of such a 2D Dirac electron system is studied for strong topological insulators in the case of the Fermi level…

Mesoscale and Nanoscale Physics · Physics 2016-09-21 Yositake Takane

We reveal a proximity effect between a topological band (Chern) insulator described by a Haldane model and spin-polarized Dirac particles of a graphene layer. Coupling weakly the two systems through a tunneling term in the bulk, the…

Mesoscale and Nanoscale Physics · Physics 2019-08-21 Peng Cheng , Philipp W. Klein , Kirill Plekhanov , Klaus Sengstock , Monika Aidelsburger , Christof Weitenberg , Karyn Le Hur

Commonly, a two-dimensional topological insulator is characterized by non-zero Chern numbers associated with its band structure. In our work, we present the experimental demonstration of an anomalous topological insulator, for which the…

The spectrum of massless Dirac electrons on the side surface of a three-dimensional weak topological insulator is significantly affected by whether the number of unit atomic layers constituting the sample is even or odd; it has a…

Mesoscale and Nanoscale Physics · Physics 2015-06-23 Yositake Takane

Topological insulators have gapless states at their boundaries while trivial insulators generically do not. We consider loops in the spaces of Hamiltonians of topologically trivial Bloch insulators, and show that there exist loops for which…

Statistical Mechanics · Physics 2011-04-12 Rahul Roy

We present a theory unifying the topological responses and anomalies of various gapless fermion systems exhibiting Fermi surfaces, including those with Berry phases, and nodal structures, which applies beyond non-interacting limit. As our…

Strongly Correlated Electrons · Physics 2025-03-07 Taylor L. Hughes , Yuxuan Wang

We study topological indices of Fermionic time-reversal invariant topological insulators in two dimensions, in the regime of strong Anderson localization. We devise a method to interpolate between certain Fredholm operators arising in the…

Mathematical Physics · Physics 2022-11-30 Alex Bols , Jeffrey Schenker , Jacob Shapiro

Quantum oscillations can be used to determine properties of the Fermi surface of metals by varying the magnitude and orientation of an external magnetic field. Topological insulator surface states are an unusual mix of normal and Dirac…

Mesoscale and Nanoscale Physics · Physics 2013-02-11 Anthony R. Wright , Ross H. McKenzie

We numerically investigate the surface states of a strong topological insulator in the presence of strong electron-electron interactions. We choose a spherical topological insulator geometry to make the surface amenable to a finite size…

Strongly Correlated Electrons · Physics 2015-07-08 T. Neupert , S. Rachel , R. Thomale , M. Greiter

We study second-order topological insulators and semimetals characterized by chiral symmetry. We investigate topological phase transitions of a model for construction of the two-dimensional second-order topological insulators protected only…

Mesoscale and Nanoscale Physics · Physics 2019-12-06 Ryo Okugawa , Shin Hayashi , Takeshi Nakanishi

We present the theory and experimental demonstration of a topological classification of finite tight binding Hamiltonians with chiral symmetry. Using the graph-theoretic notion of complete matchings, we show that many chiral tight binding…

Mesoscale and Nanoscale Physics · Physics 2024-05-28 Maxine M. McCarthy , D. M. Whittaker

Topological insulators are noninteracting, gapped fermionic systems which have gapless boundary excitations. They are characterized by topological invariants, which can be written in many different ways, including in terms of Green's…

Mesoscale and Nanoscale Physics · Physics 2011-09-29 Andrew M. Essin , Victor Gurarie

We introduce new three-dimensional topological phases of two-band models using the Pontryagin-Thom construction. In symmetry class A these are the infinitely many Hopf-Chern topological insulators, which are hybrids of layered Chern…

Mesoscale and Nanoscale Physics · Physics 2016-07-27 Ricardo Kennedy

We investigate the entanglement spectra of topological insulators which manifest edge states on a lattice with spatial boundaries. In the physical energy spectrum, a subset of the edge states that intersect the Fermi level translates to…

Mesoscale and Nanoscale Physics · Physics 2015-05-30 A. Alexandradinata , Taylor L. Hughes , B. Andrei Bernevig

We introduce topological phases of matter defined by skyrmions in the ground state spin -- or pseudospin -- expectation value textures in the Brillouin zone, the chiral and helical topological skyrmion phases of matter. These phases are…

Superconductivity · Physics 2023-03-10 Ashley M. Cook

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

Modeling the spin-triplet superconductor Sr2RuO4 through a three-orbital tight-binding model we investigate topological properties and edge states assuming chiral p-wave pairing. In concordance with experiments the three Fermi surfaces…

Superconductivity · Physics 2013-10-16 Yoshiki Imai , Katsunori Wakabayashi , Manfred Sigrist

Chern insulators are band insulators which exhibit a gap in the bulk and gapless excitations in the edge. Detection of Chern insulators is a serious challenge in cold atoms since the Hall transport measurements are technically unrealistic…

Mesoscale and Nanoscale Physics · Physics 2013-09-30 Xiong-Jun Liu , K. T. Law , T. K. Ng , Patrick A. Lee

We consider the edge and bulk conductances for 2D quantum Hall systems in which the Fermi energy falls in a band where bulk states are localized. We show that the resulting quantities are equal, when appropriately defined. An appropriate…

Mathematical Physics · Physics 2007-05-23 A. Elgart , G. M. Graf , J. H. Schenker