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Either in bulk form, or when exfoliated into atomically thin crystals, layered transition metal dichalcogenides are continuously leading to the discovery of new phenomena. The latest example is provided by 1T'-WTe$_2$, a semimetal recently…

Mesoscale and Nanoscale Physics · Physics 2017-08-23 Lin Wang , Ignacio Gutiérrez-Lezama , Céline Barreteau , Nicolas Ubrig , Enrico Giannini , A. F. Morpurgo

We selectively fabricated monolayers of octahedral (1H) and distorted trigonal (1T') WTe2 on graphene/SiC(0001) by controlling the substrate temperature during epitaxy. Angle-resolved photoemission spectroscopy, combined with…

Mesoscale and Nanoscale Physics · Physics 2025-01-30 Ryuichi Ando , Katsuaki Sugawara , Tappei Kawakami , Takashi Takahashi , Takafumi Sato

We report thermoelectric (TE) properties of topological surface Dirac states (TSDS) in three-dimensional topological insulators (3D-TIs) purely isolated from the bulk by employing single crystal Bi$_{2-x}$Sb$_x$Te$_{3-y}$Se$_y$ films…

Twisted bilayers of two-dimensional (2D) materials are proving a fertile ground for investigating strongly correlated electron phases. This is because the moir\'e pattern introduced by the relative twist between layers introduces…

Materials Science · Physics 2021-10-13 Hao Tang , Stephen Carr , Efthimios Kaxiras

By using first-principles calculations, we propose that ZrSiO can be looked as a three-dimensional (3D) oxide weak topological insulator (TI) and its single layer is a long-sought-after 2D oxide TI with a band gap up to 30 meV. Calculated…

Materials Science · Physics 2015-12-02 Qiunan Xu , Zhida Song , Simin Nie , Hongming Weng , Zhong Fang , Xi Dai

Single-layer transition metal dichalcogenide (TMD) WSe2 has recently attracted a lot of attention because it is a 2D semiconductor with a direct band-gap. Due to low doping levels it is intrinsic and shows ambipolar transport. This opens up…

Mesoscale and Nanoscale Physics · Physics 2014-07-18 Adrien Allain , Andras Kis

The major breakthroughs in the understanding of topological materials over the past decade were all triggered by the discovery of the Z$_2$ topological insulator (TI). In three dimensions (3D), the TI is classified as either "strong" or…

Monolayer (ML) transition-metal dichalcogenides exist in different phases, such as the hexagonal (2H) and distorted octahedral or monoclinic (1T') phases. The different structures show vastly different properties. For example, the 2H MoTe2…

Materials Science · Physics 2017-04-26 Jinglei Chen , Guanyong Wang , Yanan Tang , Jinpeng Xu , Xianqi Dai , Jinfeng Jia , Wingkin Ho , Maohai Xie

By using angle-resolved photoemission spectroscopy combined with first-principles calculations, we reveal that the topmost unit cell of ZrSnTe crystal hosts two-dimensional (2D) electronic bands of topological insulator (TI) state, though…

The most interesting experimental results obtained in studies of 2D and 3D topological insulators (TIs) based on HgTe quantum wells and films are reviewed. In the case of 2D TIs, these include the observation of nonlocal ballistic and…

Mesoscale and Nanoscale Physics · Physics 2020-12-29 Z. D. Kvon , D. A. Kozlov , E. B. Olshanetsky , G. M. Gusev , N. N. Mikhailov , S. A. Dvoretsky

Freestanding single-bilayer Bi(111) is a two-dimensional topological insulator with edge states propagating along its perimeter. Given the interlayer coupling experimentally, the topological nature of Bi(111) thin films and the impact of…

Materials Science · Physics 2018-12-10 Lang Peng , Jing-Jing Xian , Peizhe Tang , Angel Rubio , Shou-Cheng Zhang , Wenhao Zhang , Ying-Shuang Fu

Three-dimensional (3-D) topological insulators (TI) are characterized by the presence of metallic surface states and a bulk band gap. Recently theoretical and experimental studies have shown an induced gap in the surface state bands of TI…

Mesoscale and Nanoscale Physics · Physics 2012-12-21 Jiwon Chang , Leonard F. Register , Sanjay K. Banerjee

A WSe2 monolayer of 1T' phase is a large band gap quantum spin Hall insulator, supporting dissipationless charge and spin transports through the topologically protected edge states. In this work, we explore the nanoribbon forms of 1T' phase…

Mesoscale and Nanoscale Physics · Physics 2023-02-28 Hong Tang , Jason M. Breslin , Li Yin , Adrienn Ruzsinszky

Employing ab initio electronic calculations, we propose a new type of two-dimensional (2D) topological insulator (TI), monolayer (ML) low buckled (LB) mercury telluride (HgTe) and mercury selenide (HgSe), with tunable band gaps. Monolayer…

Mesoscale and Nanoscale Physics · Physics 2015-10-19 Jin Li , Chaoyu He , Lijun Meng , Huaping Xiao , Chao Tang , Xiaolin Wei , Jinwoong Kim , Nicholas Kioussis , G. Malcolm Stocks , Jianxin Zhong

The paradigm of classifying three-dimensional (3D) topological insulators into strong and weak ones (STI and WTI) opens the door for the discovery of various topological phases of matter protected by different symmetries and defined in…

A quantum spin Hall insulator hosts topological states at the one-dimensional edge, along which backscattering by nonmagnetic impurities is strictly prohibited and dissipationless current flows. Its 3D analogue, a weak topological insulator…

Most metallic transition metal dichalcogenides undergo charge density wave (CDW) instabilities with similar or identical ordering vectors in bulk and in single layer, albeit with different critical temperatures. Metallic 1T-TiTe$_2$ is a…

A topological insulator possesses a bulk energy gap splitting the lowest empty band from the highest occupied electronic band. The electronic states at the surface (or edge in two dimensions), on the other hand, of a topological insulator…

Materials Science · Physics 2020-05-28 Md. Asif Afzal , S. H. Naqib

Dimensional evolution between one- ($1D$) and two-dimensional ($2D$) topological phases is investigated systematically. The crossover from a $2D$ topological insulator to its $1D$ limit shows oscillating behavior between a $1D$ ordinary…

Mesoscale and Nanoscale Physics · Physics 2015-06-19 Huaiming Guo , Lin Yang , Shun-Qing Shen

A van der Waals material, MoTe2 with a monoclinic 1T' crystal structure is a candidate for three-dimensional (3D) second-order topological insulators (SOTIs) hosting gapless hinge states and insulating surface states. However, due to the…