Conductance of gated junctions as a probe of **topological** interface
states

**topological**

**insulators**(TIs) and non-topological materials depend on the charge redistribution, strain, and atomic displacement at the interface. Expand abstract.

**topological**

**insulators**(TIs) and non-

**topological**materials depend on the charge redistribution, strain, and atomic displacement at the interface. Knowledge of these properties is essential for applications of

**topological**compounds, but direct access to them in the interface geometry is difficult. We show that conductance of a gated double junction at the surface of a

**topological**

**insulator**exhibits oscillations and a quasi-linear decay as a function of gate voltage in different regimes. These give the values for the quasiparticle velocities along and normal to the junction in the interface region, and determine the symmetry of the

**topological**interface states. The results are insensitive to the boundary conditions at the junction.

6/10 relevant

arXiv

First Principles Modeling of **Topological** **Insulators**: Structural
Optimization and Exchange Correlation Functionals

**Topological**

**insulators**(TIs) are materials that are insulating in the bulk but have zero band gap surface states with linear dispersion and are protected by time reversal symmetry. These unique characteristics could pave the way for many promising applications that include spintronic devices and quantum computations. It is important to understand and theoretically describe TIs as accurately as possible in order to predict properties. Quantum mechanical approaches, specifically first principles density functional theory (DFT) based methods, have been used extensively to model electronic properties of TIs. Here, we provide a comprehensive assessment of a variety of DFT formalisms and how these capture the electronic structure of TIs. We concentrate on Bi$_2$Se$_3$ and Bi$_2$Te$_3$ as examples of prototypical TI materials. We find that the generalized gradient (GGA) and kinetic density functional (metaGGA) produce displacements increasing the thickness of the TI slab, whereas we see an opposite behavior in DFT computations using LDA. Accounting for van der Waals (vdW) interactions overcomes the apparent over-relaxations and retraces the atomic positions towards the bulk. Based on an intensive computational study, we show that GGA with vdW treatment is the most appropriate method for structural optimization. Electronic structures derived from GGA or metaGGA employing experimental lattice parameters are also acceptable. In this regard, we express a slight preference for metaGGA in terms of accuracy, but an overall preference for GGA due to compensatory improvements in computability in capturing TI behavior.

10/10 relevant

arXiv

**Topological** Properties of \tau-Type Organic Conductors with a
Checkerboard Lattice

**topological**

**insulators**, which could exhibit finite spin Hall effect. Expand abstract.

**topological**phases are difficult to be realized in organic molecular crystals, we demonstrate here that they can emerge in the \tau-type organic layered conductors, \tau-(EDO-S,S-DMEDT-TTF)_2X_{1+y} and \tau-(P-S,S-DMEDT-TTF)_2X_{1+y} (X=AuBr_2, I_3, IBr_2), where EDO-S,S-DMEDT-TTF and P-S,S-DMEDT-TTF denote the planar donor molecules ethylenedioxy-S,S-dimethyl(ethylenedithio)tetrathiafulvalene and pyrazino-S,S-dimethyl(ethylenedithio)tetrathiafulvalene, respectively. The conducting layers of these conductors have a highly symmetric checkerboard structure, which can be regarded as a modified Mielke lattice. Because their electronic structure inherits that of the Mielke lattice, their conduction and valence bands exhibits the quadratic band touching. The contact point splits into a pair of Dirac cones under uniaxial strain which breaks C_4-symmetry. In \tau-type conductors, we can expect rather large spin-orbit coupling (SOC) as organic conductors. We show that the SOC in this case opens a topologically nontrivial gap at the band contact point, and the helical edge states exist in the gap. The actual \tau-type conductors could be regarded as heavily-doped

**topological**insulators, which could exhibit finite spin Hall effect.

4/10 relevant

arXiv

Transport in two-dimensional **topological** materials: recent developments
in experiment and theory

**insulators**are finding applications in magnetic devices, while Hall transport in doped samples and the general issue of

**topological**protection remain controversial. Expand abstract.

**Topological**

**insulators**are finding applications in magnetic devices, while Hall transport in doped samples and the general issue of

**topological**protection remain controversial. In transition metal dichalcogenides valley-dependent electrical and optical phenomena continue to stimulate state-of-the-art experiments. In Weyl semimetals the properties of Fermi arcs are being actively investigated. A new field, expected to grow in the near future, focuses on the non-linear electrical and optical responses of

**topological**materials, where fundamental questions are once more being asked about the intertwining roles of the Berry curvature and disorder scattering. In

**topological**superconductors the quest for chiral superconductivity, Majorana fermions and

**topological**quantum computing is continuing apace.

4/10 relevant

arXiv

The classification of surface states of **topological** **insulators** and
superconductors with magnetic point group symmetry

**topological**

**insulators**and superconductors protected by crystallographic magnetic point group symmetry in three spatial dimensions. Recently, Cornfeld and Chapman [Phys. Rev. B {\bf 99}, 075105 (2019)] pointed out that the

**topological**classification of mass terms of the Dirac Hamiltonian with point group symmetry is recast as the extension problem of the Clifford algebra, and we use their results extensively. Comparing two-types of Dirac Hamiltonians with and without the mass-hedgehog potential, we establish the irreducible character formula to read off which Hamiltonian in the whole $K$-group belongs to fourth-order

**topological**phases, which are atomic

**insulators**localized at the center of the point group.

10/10 relevant

arXiv

Disorder effects in InAs/GaSb **topological** **insulator** candidates

5/10 relevant

arXiv

Edelstein and inverse Edelstein effects caused by the pristine surface
states of **topological** **insulators**

**topological**

**insulators**is investigated by means of a semiclassical approach. Expand abstract.

**topological**

**insulators**is investigated by means of a semiclassical approach. The combined effect of random impurity scattering and the spin-momentum locking of the gapless Dirac cone yields a current-induced surface spin accumulation independent from chemical potential and temperature. Through combing the semiclassical approach with the Bloch equation, the inverse Edelstein effect that converts the spin pumping spin current into a charge current is well explained. Consistency of these results with various experiments will be elaborated in detail.

10/10 relevant

arXiv

Joule meets van der Waals: Mechanical dissipation via image potential
states on a **topological** **insulator** surface

**topological**

**insulator**surface. Expand abstract.

**topological**

**insulator**surfaces of Bi2Te3, where common Joule dissipation was observed to be suppressed due to topologically protected surface states. Thus, a novel type of dissipation mechanism is observed by pendulum AFM, which is related to single electron tunneling resonances into image potential states that are slightly above the Bi2Te3 surface. The application of a magnetic field leads to the break down of the

**topological**protection of the surface states and restores the expected Joule dissipation process. Nanomechanical energy dissipation experienced by the cantilever of pendulum AFM provides a novel source of information on the dissipative nature of the quantum-tunneling phenomena on the

**topological**

**insulator**surface.

8/10 relevant

arXiv

First-principles prediction of a new family of layered **topological**
**insulators**

**topological**

**insulators**(TIs), two strong

**topological**metals (TMs) and nearly twenty trivial

**insulators**at their equilibrium structures. The TIs are in the (1;111)

**topological**class, with energy gaps ranging from 0.04 to 0.2 eV. The strong TMs and the trivial

**insulators**belong to the (1;111) and (0;000)

**topological**classes, respectively. Small compressive strains easily turn some of the trivial

**insulators**into strong TIs. This study enriches not only the family of

**topological**materials but also the family of van der Waals layered materials, providing promising candidates for the future spintronic devices.

10/10 relevant

arXiv

Dirac surface states in intrinsic magnetic **topological** **insulators**
EuSn2As2 and MnBi2nTe3n+1

**topological**

**insulators**(TIs), the interplay between magnetic order and nontrivial topology can induce fascinating

**topologic**al quantum phenomena, such as the quantum anomalous Hall effect, chiral Majorana fermions and axion electrodynamics. Expand abstract.

**topological**

**insulators**(TIs), the interplay between magnetic order and nontrivial topology can induce fascinating

**topological**quantum phenomena, such as the quantum anomalous Hall effect, chiral Majorana fermions and axion electrodynamics. Recently, a great deal of attention has been focused on the intrinsic magnetic TIs, where disorder effects can be eliminated to a large extent, which is expected to facilitate the emergence of

**topological**quantum phenomena. In despite of intensive efforts, experimental evidence of the

**topological**surface states (SSs) remains elusive. Here, by combining first-principles calculations and angle-resolved photoemission spectroscopy (ARPES) experiments, we have revealed that EuSn2As2 is an antiferromagnetic TI with observation of Dirac SSs consistent with our prediction. We also observe nearly gapless Dirac SSs in antiferromagnetic TIs MnBi2nTe3n+1 (n = 1 and 2), which were absent in previous ARPES results. These results provide clear evidence for nontrivial topology of these intrinsic magnetic TIs. Furthermore, we find that the

**topological**SSs show no observable changes across the magnetic transition within the experimental resolution, indicating that the magnetic order has quite small effect on the

**topological**SSs, which can be attributed to weak hybridization between the localized magnetic moments, from either 4f or 3d orbitals, and the

**topological**electronic states. This provides insights for further research that the correlations between magnetism and

**topological**states need to be strengthened to induce larger gaps in the

**topological**SSs, which will facilitate the realization of

**topological**quantum phenomena at higher temperatures.

10/10 relevant

arXiv