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We investigated the precise crystal structures and electronic states in a quasi-two-dimensional molecular conductor ${\alpha}$-(BETS)$_2$I$_3$ at ambient pressure. The electronic resistivity of this molecular solid shows metal-to-insulator…

We report semiconductor to metal-like crossover in temperature dependence of resistivity ($\rho$) due to the switching of charge transport from bulk to surface channel in three-dimensional topological insulator…

Materials Science · Physics 2017-07-10 Prithwish Dutta , Arnab Pariari , Prabhat Mandal

The extent to which disorder influences the properties of topological semimetals remains an open question and is relevant to both the understanding of topological states and the use of topological materials in practical applications. Here,…

State-of-the-art topological devices require the use topological surface states to drive electronic transport. In this study, we examine a tunable topological system, $Ge(Bi_{x}Sb_{1-x})_{2}Te_{4}$, for a range of 'x' values from 0 to 1,…

The surface states of a topological insulator are described by an emergent relativistic massless Dirac equation in 2+1 dimensions. In contrast to graphene, there is an odd number of Dirac points, and the electron spin is directly coupled to…

Mesoscale and Nanoscale Physics · Physics 2013-05-29 Qin Liu , Chao-Xing Liu , Cenke Xu , Xiao-Liang Qi , Shou-Cheng Zhang

We calculate the local density of states of two prototypical topological insulators (Bi$_2$Se$_3$ and Bi$_2$Te$_2$Se) as a function of distance from the surface within density functional theory. We find that, in the absence of disorder or…

Mesoscale and Nanoscale Physics · Physics 2015-10-08 Benjamin M. Fregoso , Sinisa Coh

We study superconductivity in a three-dimensional zero-density Dirac semimetal in proximity to a ferroelectric quantum critical point. We find that the interplay of criticality, inversion-symmetry breaking, and Dirac dispersion gives rise…

Superconductivity · Physics 2022-11-30 Vladyslav Kozii , Avraham Klein , Rafael M. Fernandes , Jonathan Ruhman

The electrons found in Dirac materials are notorious for being difficult to manipulate due to the Klein phenomenon and absence of backscattering. Here we investigate how spatial modulations of the Fermi velocity in two-dimensional Dirac…

Mesoscale and Nanoscale Physics · Physics 2017-07-10 C. A. Downing , M. E. Portnoi

We report a unified theory based on linear response, for analyzing the longitudinal optical conductivity (LOC) of materials with tilted Dirac cones. Depending on the tilt parameter $t$, the Dirac electrons have four phases: untilted,…

Mesoscale and Nanoscale Physics · Physics 2023-11-27 Jian-Tong Hou , Chang-Xu Yan , Chao-Yang Tan , Zhi-Qiang Li , Peng Wang , Hong Guo , Hao-Ran Chang

In the present work, we investigated the electronic and elastic properties in equilibrium and under strain of the type-II Dirac semimetal NiTe$_2$ using density functional theory (DFT). Our results demonstrate the tunability of Dirac nodes'…

Topological semimetals, such as Dirac, Weyl, or line-node semimetals, are gapless states of matter characterized by their nodal band structures and surface states. In this work, we consider layered (topologically trivial) insulating systems…

Mesoscale and Nanoscale Physics · Physics 2022-05-12 Saavanth Velury , Taylor L. Hughes

We have designed three-dimensional models of topological insulator thin films, showing a tunability of the odd number of Dirac cones on opposite surfaces driven by the atomic-scale geometry at the boundaries. This enables creation of a…

Mesoscale and Nanoscale Physics · Physics 2013-01-03 David Soriano , Frank Ortmann , Stephan Roche

The non-trivial topology of the three-dimensional (3D) topological insulator (TI) dictates the appearance of gapless Dirac surface states. Intriguingly, when a 3D TI is made into a nanowire, a gap opens at the Dirac point due to the quantum…

Mesoscale and Nanoscale Physics · Physics 2021-05-05 Felix Münning , Oliver Breunig , Henry F. Legg , Stefan Roitsch , Dingxun Fan , Matthias Rößler , Achim Rosch , Yoichi Ando

We study the conductance fluctuation in topological semimetals. Through statistic distribution of energy levels of topological semimetals, we determine the dominant parameters of universal conductance fluctuation (UCF), i.e., the number of…

Disordered Systems and Neural Networks · Physics 2017-10-25 Yayun Hu , Haiwen Liu , Hua Jiang , X. C. Xie

We analyze the scaling behavior at and near a quantum critical point separating a semimetallic from a superfluid phase. To this end we compute the renormalization group flow for a model of attractively interacting electrons with a linear…

Strongly Correlated Electrons · Physics 2011-11-08 Benjamin Obert , So Takei , Walter Metzner

Electrons on a square lattice with half a flux quantum per plaquette are considered. An effective description for the current loops is given by a two-dimensional Dirac theory with random mass. It is shown that the conductivity and the…

Condensed Matter · Physics 2009-10-28 K. Ziegler

The intrinsically superconducting Dirac semimetal 2M-WS$_{2}$ is a promising candidate to realize proximity-induced topological superconductivity in its protected surface states. A precise characterization of the bulk superconducting state…

Topological insulators (TIs) are said to be stable against non-magnetic impurity scattering due to suppressed backscattering in the Dirac surface states. We solve a lattice model of a three-dimensional TI in the presence of strong potential…

Mesoscale and Nanoscale Physics · Physics 2015-05-30 Annica M. Black-Schaffer , Alexander V. Balatsky

We adapt a finite difference method of solution of the two-dimensional massless Dirac equation, developed in the context of lattice gauge theory, to the calculation of electrical conduction in a graphene sheet or on the surface of a…

Mesoscale and Nanoscale Physics · Physics 2009-01-02 J. Tworzydlo , C. W. Groth , C. W. J. Beenakker

We propose helical topological superconductivity away from the Fermi surface in three-dimensional time-reversal-symmetric odd-parity multiband superconductors. In these systems, pairing between electrons originating from different bands is…

Mesoscale and Nanoscale Physics · Physics 2024-07-01 Masoud Bahari , Song-Bo Zhang , Chang-An Li , Sang-Jun Choi , Philipp Rüßmann , Carsten Timm , Björn Trauzettel