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We investigated the relative stability of the amorphous vs crystalline nanoparticles of size ranging between 0.8 and 1.8 nm. We found that, at variance from bulk systems, at low T small nanoparticles are amorphous and they undergo to an…

Mesoscale and Nanoscale Physics · Physics 2015-05-27 Sergio Orlandini , Simone Meloni , Luciano Colombo

Intrinsically broken symmetries in the bulk of topological insulators (TIs) are manifested in their surface states. In spite of particle-hole asymmetry in TIs, it has often been assumed that their surface states are characterized by a…

Mesoscale and Nanoscale Physics · Physics 2024-09-02 Mahmoud M. Asmar , Gaurav Gupta , Wang-Kong Tse

We study transport and optical properties of the surface states which lie in the bulk energy gap of a thin-film topological insulator. When the film thickness is comparable with the surface state decay length into the bulk, the tunneling…

Mesoscale and Nanoscale Physics · Physics 2010-03-04 Hai-Zhou Lu , Wen-Yu Shan , Wang Yao , Qian Niu , Shun-Qing Shen

Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), an experimental and theoretical study of changes in the electronic structure (dispersion dependencies) and corresponding modification of the energy…

We investigate a topological switch between second-order topological insulators (SOTIs) and topological crystalline insulators (TCIs). Both the SOTI and the TCI are protected by the mirror and inversion symmetries, for which we define the…

Mesoscale and Nanoscale Physics · Physics 2018-09-19 Motohiko Ezawa

Topological semimetals are systems in which the conduction and the valence bands cross each other and this crossing is protected by topological constraints. These materials provide an intriguing test of fundamental theory and their…

Strongly Correlated Electrons · Physics 2017-05-25 Marcin Matusiak , J. R. Cooper , Dariusz Kaczorowski

Topological insulators are bulk semiconductors that manifest in-gap massless Dirac surface states due to the topological bulk-boundary correspondence principle [1-3]. These surface states have been a subject of tremendous ongoing interest,…

We describe a three-dimensional crystalline topological insulator (TI) phase of matter that exhibits spontaneous polarization. This polarization results from the presence of (approximately) flat bands on the surface of such TIs. These flat…

Materials Science · Physics 2021-06-16 J. Nissinen , Tero T. Heikkila , G. E. Volovik

Sources of quantum light, in particular correlated photon pairs that are indistinguishable in all degrees of freedom, are the fundamental resource that enables continuous-variable quantum computation and paradigms such as Gaussian boson…

The non-trivialness of a topological insulator (TI) is characterized either by a bulk topological invariant or by the existence of a protected metallic surface state. Yet, in realistic samples of finite size this non-trivialness does not…

Mesoscale and Nanoscale Physics · Physics 2013-01-08 Ken-Ichiro Imura , Mayuko Okamoto , Yukinori Yoshimura , Yositake Takane , Tomi Ohtsuki

A general partial-wave multiple scattering theory for scattering from cylindrically symmetric potentials on a topological insulator (TI) surface is developed. As an application, the cross sections for a single scatterer and two scatterers…

Mesoscale and Nanoscale Physics · Physics 2011-12-09 Zhen-Guo Fu , Ping Zhang , Zhigang Wang , Shu-Shen Li

Bi$_{2}$Te$_{3}$ and Bi$_{2}$Se$_{3}$ are well known 3D-topological insulators. Films made of these materials exhibit metal-like surface states with a Dirac dispersion and possess high mobility. The high mobility metal-like surface states…

Mesoscale and Nanoscale Physics · Physics 2015-06-22 Parijat Sengupta , Tillmann Kubis , Yaohua Tan , Gerhard Klimeck

Topological invariants are a significant ingredient in the study of topological phases of matter that intertwines the supposedly contradicting concepts of bulk and boundary. The nature of the invariants differ depending on the dimension of…

Mesoscale and Nanoscale Physics · Physics 2023-11-28 Srijata Lahiri , Saurabh Basu

We introduce a combined Restrained MD/Parallel Tempering approach to study the difference in free energy as a function of a set of collective variables between two states in presence of unknown slow degrees of freedom. We applied this…

Statistical Mechanics · Physics 2015-03-19 Simone Meloni , Sergio Orlandini , Giovanni Ciccotti

Topological insulators are transformative quantum solids with immune-to-disorder metallic surface states having Dirac band structure. Ubiquitous charged bulk defects, however, pull the Fermi energy into the bulk bands, denying access to…

We consider surface states in semiconductors with inverted-band structures, such as $\alpha$-Sn and HgTe. The main interest is the interplay of the effect of a strain of an arbitrary sign and that of the sample finite size. We consider, in…

Mesoscale and Nanoscale Physics · Physics 2024-09-24 Alexander Khaetskii , Vitaly Golovach , Arnold Kiefer

The quantum superposition principle is a cornerstone of physics and at the heart of many quantum technologies. Yet, it is still often regarded counterintuitive because we do not observe its key features on the macroscopic scales of our…

We theoretically study the electronic structure and spin properties of one-dimensional nanostructures of the prototypical bulk topological insulator Bi$_2$Se$_3$. Realistic models of experimentally observed Bi$_2$Se$_3$ nanowires and…

Mesoscale and Nanoscale Physics · Physics 2018-04-13 Naunidh Virk , Gabriel Autès , Oleg V. Yazyev

In the recently discovered class of materials known as topological insulators, the presence of strong spin-orbit coupling causes certain topological invariants in the bulk to differ from their values in vacuum. The sudden change of…

The interplay between magnetism and non-trivial topology in magnetic topological insulators (MTI) is expected to give rise to a variety of exotic topological quantum phenomena, such as the quantum anomalous Hall (QAH) effect and the…