Emergence of magnetic topological states in topological insulators doped with magnetic impurities

ABSTRACTWe present results of theoretical studies of transition metal dopants in GaAs, based on microscopic tight-binding model and ab-initio calculations. We focus in particular on how the vicinity of surface affects the properties of the hole-acceptor state, its magnetic anisotropy and its magnetic coupling to the magnetic dopant. In agreement with STM experiments, Mn substitutional dopants on the (110) GaAs surface give rise to a deep acceptor state, whose wavefunction is localized around the Mn center. We discuss a refinement of the theory that introduces explicitly the d-levels for the TM dopant. The explicit inclusion of d-levels is particularly important for addressing recent STM experiments on substitutional Fe in GaAs. In the second part of the paper we discuss an analogous investigation of single dopants in Bi2Se3 three-dimensional topological insulators, focusing in particular on how substitutional impurities positioned on the surface affect the electronic structure in the gap. We present explicit results for BiSe antisite defects and compare with STM experiments.

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Contribution of 1D topological states to the extraordinary thermoelectric properties of Bi 2 Te 3

Proceedings of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rspa.2020.0088 ◽

2020 ◽

Vol 476 (2239) ◽

pp. 20200088

Author(s):

P. Chudzinski

Keyword(s):

Thermoelectric Properties ◽

Topological Insulators ◽

Three Dimensional ◽

Luttinger Liquid ◽

Dislocation Network ◽

Finite Frequency ◽

Structured Materials ◽

One Dimensional ◽

Topological States ◽

Analytical Formulae

Topological insulators are frequently also one of the best-known thermoelectric materials. It has been recently discovered that in three-dimensional (3D) topological insulators each skew dislocation can host a pair of one-dimensional (1D) topological states—a helical Tomonaga–Luttinger liquid (TLL). We derive exact analytical formulae for thermoelectric Seebeck coefficient in TLL and investigate up to what extent one can ascribe the outstanding thermoelectric properties of Bi 2 Te 3 to these 1D topological states. To this end we take a model of a dense dislocation network and find an analytic formula for an overlap between 1D (the TLL) and 3D electronic states. Our study is applicable to a weakly n -doped Bi 2 Te 3 but also to a broader class of nano-structured materials with artificially created 1D systems. Furthermore, our results can be used at finite frequency settings, e.g. to capture transport activated by photo-excitations.

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Topological states between inversion symmetric atomic insulators

SciPost Physics ◽

10.21468/scipostphys.10.6.137 ◽

2021 ◽

Vol 10 (6) ◽

Author(s):

Ana Silva ◽

Jasper van Wezel

Keyword(s):

Topological Insulators ◽

Group Representation ◽

Topological Invariant ◽

Topological Invariants ◽

Atomic Lattice ◽

Space Group ◽

Topological Materials ◽

Boundary Correspondence ◽

Symmetric Band ◽

Topological States

One of the hallmarks of topological insulators is the correspondence between the value of its bulk topological invariant and the number of topologically protected edge modes observed in a finite-sized sample. This bulk-boundary correspondence has been well-tested for strong topological invariants, and forms the basis for all proposed technological applications of topology. Here, we report that a group of weak topological invariants, which depend only on the symmetries of the atomic lattice, also induces a particular type of bulk-boundary correspondence. It predicts the presence or absence of states localised at the interface between two inversion-symmetric band insulators with trivial values for their strong invariants, based on the space group representation of the bands on either side of the junction. We show that this corresponds with symmetry-based classifications of topological materials. The interface modes are protected by the combination of band topology and symmetry of the interface, and may be used for topological transport and signal manipulation in heterojunction-based devices.

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Ordering of Magnetic Impurities and Tunable Electronic Properties of Topological Insulators

Physical Review Letters ◽

10.1103/physrevlett.106.136802 ◽

2011 ◽

Vol 106 (13) ◽

Cited By ~ 151

Author(s):

D. A. Abanin ◽

D. A. Pesin

Keyword(s):

Electronic Properties ◽

Topological Insulators ◽

Magnetic Impurities

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Non-Hermitian topological light steering

Science ◽

10.1126/science.aay1064 ◽

2019 ◽

Vol 365 (6458) ◽

pp. 1163-1166 ◽

Cited By ~ 53

Author(s):

Han Zhao ◽

Xingdu Qiao ◽

Tianwei Wu ◽

Bikashkali Midya ◽

Stefano Longhi ◽

...

Keyword(s):

Topological Insulator ◽

Topological Insulators ◽

Dynamic Control ◽

High Density ◽

Light Transport ◽

Practical Applications ◽

Data Capacity ◽

Topological States ◽

Topological State ◽

Robust Transmission

Photonic topological insulators provide a route for disorder-immune light transport, which holds promise for practical applications. Flexible reconfiguration of topological light pathways can enable high-density photonics routing, thus sustaining the growing demand for data capacity. By strategically interfacing non-Hermitian and topological physics, we demonstrate arbitrary, robust light steering in reconfigurable non-Hermitian junctions, in which chiral topological states can propagate at an interface of the gain and loss domains. Our non-Hermitian–controlled topological state can enable the dynamic control of robust transmission links of light inside the bulk, fully using the entire footprint of a photonic topological insulator.

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Dissipation-induced topological insulators: A no-go theorem and a recipe

SciPost Physics ◽

10.21468/scipostphys.7.5.067 ◽

2019 ◽

Vol 7 (5) ◽

Cited By ~ 8

Author(s):

Moshe Goldstein

Keyword(s):

Topological Insulators ◽

Hamiltonian Dynamics ◽

Cold Atom ◽

Atomic Gases ◽

Finite Range ◽

Many Body ◽

Topological States ◽

Range Dynamics ◽

Nonequilibrium Conditions ◽

General Answer

Nonequilibrium conditions are traditionally seen as detrimental to the appearance of quantum-coherent many-body phenomena, and much effort is often devoted to their elimination. Recently this approach has changed: It has been realized that driven-dissipative dynamics could be used as a resource. By proper engineering of the reservoirs and their couplings to a system, one may drive the system towards desired quantum-correlated steady states, even in the absence of internal Hamiltonian dynamics. An intriguing category of equilibrium many-particle phases are those which are distinguished by topology rather than by symmetry. A natural question thus arises: which of these topological states can be achieved as the result of dissipative Lindblad-type (Markovian) evolution? Beside its fundamental importance, it may offer novel routes to the realization of topologically-nontrivial states in quantum simulators, especially ultracold atomic gases. Here I give a general answer for Gaussian states and quadratic Lindblad evolution, mostly concentrating on the example of 2D Chern insulator states. I prove a no-go theorem stating that a finite-range Lindbladian cannot induce finite-rate exponential decay towards a unique topological pure state above 1D. I construct a recipe for creating such state by exponentially-local dynamics, or a mixed state arbitrarily close to the desired pure one via finite-range dynamics. I also address the cold-atom realization, classification, and detection of these states. Extensions to other types of topological insulators and superconductors are also discussed.

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