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We use ultrafast laser pulses to experimentally demonstrate that the second-order optical response of bulk single crystals of the topological insulator Bi$_2$Se$_3$ is sensitive to its surface electrons. By performing surface doping…

Materials Science · Physics 2011-02-02 D. Hsieh , J. W. McIver , D. H. Torchinsky , D. R. Gardner , Y. S. Lee , N. Gedik

We show that non-trivial two-dimensional topological insulators protected by an odd time-reversal symmetry have absolutely continuous edge spectrum. The proof employs a time-reversal symmetric version of the Wold decomposition that singles…

Mathematical Physics · Physics 2024-10-08 Alex Bols , Christopher Cedzich

The discovery that the band structure of electronic insulators may be topologically non-trivial has unveiled distinct phases of electronic matter with novel properties. Recently, mechanical lattices have been found to have similarly rich…

Mesoscale and Nanoscale Physics · Physics 2018-10-10 Noah P. Mitchell , Lisa M. Nash , Daniel Hexner , Ari Turner , William T. M. Irvine

Motivated by the recent rapid development of the field of quantum gases in optical lattices, we present a comprehensive study of the spectrum of ultracold atoms in a one-dimensional optical lattice subjected to a periodic lattice…

Quantum Gases · Physics 2011-10-11 Jia-Wei Huo , Fu-Chun Zhang , Weiqiang Chen , M. Troyer , U. Schollwöck

We systematically investigate the topological properties of spin polarized Rydberg-dressed fermionic atoms loaded in a bilayer optical lattice. Through tuning the Rydberg coupling strength and the inter-layer tunneling amplitude, we…

Superconductivity · Physics 2022-07-20 Ching-Yu Huang , Jiapei Zhuang , Po-Yao Chang , Daw-Wei Wang

Conventional topological insulators and superconductors have topologically protected nodal points on their boundaries, and the recent interests in nodal-line semimetals only concerned bulk band structures. Here, we present a novel…

Mesoscale and Nanoscale Physics · Physics 2018-05-21 L. B. Shao , Y. X. Zhao

We present a direct measurement of the density profile of a two-dimensional Mott Insulator formed by ultracold atoms in an optical lattice. High resolution absorption imaging is used to probe the "wedding-cake" structure of a trapped gas as…

Quantum Gases · Physics 2009-08-21 Nathan Gemelke , Xibo Zhang , Chen-Lung Hung , Cheng Chin

We present mathematical details of the construction of a topological invariant for periodically driven two-dimensional lattice systems with time-reversal symmetry and quasienergy gaps, which was proposed recently by some of us. The…

Mesoscale and Nanoscale Physics · Physics 2015-05-25 David Carpentier , Pierre Delplace , Michel Fruchart , Krzysztof Gawędzki , Clément Tauber

We define a class of insulators with gapless surface states protected from localization due to the statistical properties of a disordered ensemble, namely due to the ensemble's invariance under a certain symmetry. We show that these…

Mesoscale and Nanoscale Physics · Physics 2014-04-23 I. C. Fulga , B. van Heck , J. M. Edge , A. R. Akhmerov

A powerful result of topological band theory is that nontrivial phases manifest obstructions to constructing localized Wannier functions. In Chern insulators, it is impossible to construct Wannier functions that respect translational…

Mesoscale and Nanoscale Physics · Physics 2022-08-11 Todd Van Mechelen , Robert-Jan Slager , Sathwik Bharadwaj , Zubin Jacob

Electrons hopping on the sites of a three-dimensional pyrochlore lattice are shown to form topologically non-trivial insulating phases when the spin-orbit (SO) coupling and lattice distortions are present. Of 16 possible topological classes…

Mesoscale and Nanoscale Physics · Physics 2015-05-13 H. -M. Guo , M. Franz

In the quest for topological insulators with large band gaps, heterostructures with Rashba spin-orbit interactions come into play. Transition metal oxides with heavy ions are especially interesting in this respect. We discuss the design…

Mesoscale and Nanoscale Physics · Physics 2020-11-17 Pieter M. Gunnink , Rosa Luca Bouwmeester , Alexander Brinkman

The realization of topological states of matter in ultracold atomic gases is currently the subject of intense experimental activity. Using a synthetic dimension, encoded in a non-spatial degree of freedom, can greatly simplify the…

Quantum Gases · Physics 2023-12-14 Aurélien Fabre , Sylvain Nascimbene

A topology optimization method is presented for the design of periodic microstructured materials with prescribed homogenized nonlinear constitutive properties over finite strain ranges. The mechanical model assumes linear elastic isotropic…

Computational Engineering, Finance, and Science · Computer Science 2020-05-20 Reza Behrou , Maroun Abi Ghanem , Brianna C. Macnider , Vimarsh Verma , Ryan Alvey , Jinho Hong , Ashley F. Emery , Hyunsun Alicia Kim , Nicholas Boechler

Topological insulators (TIs) are an emerging class of materials that host highly robust in-gap surface/interface states while maintaining an insulating bulk. While most notable scientific advancements in this field have been focused on TIs…

We adapt the topological quantum chemistry formalism to layer groups, and apply it to study the band topology of 8,872 entries from the computational two-dimensional (2D) materials databases C2DB and MC2D. In our analysis, we find 4,073…

Mesoscale and Nanoscale Physics · Physics 2024-11-15 Urko Petralanda , Yi Jiang , B. Andrei Bernevig , Nicolas Regnault , Luis Elcoro

It is shown theoretically that a one-dimensional crystal with time reversal symmetry is characterized by a Z_{2} topological invariant that predicts the existence or otherwise of edge states. This is confirmed experimentally through the…

Mesoscale and Nanoscale Physics · Physics 2016-03-09 Timothy J. Atherton , Celia A. M. Butler , Melita C. Taylor , Ian R. Hooper , Alastair P. Hibbins , J. Roy Sambles , Harsh Mathur

The recent discoveries about topological insulators have been promoting theoretical and experimental research. In this dissertation, the basic concepts of topological insulators and the Quantum Hall Effect are reviewed focusing the…

Mesoscale and Nanoscale Physics · Physics 2022-05-04 Manuel B. Santos

We studied electronic band structure and topological property of a topological insulator thin film under a moir\'e superlattice potential to search for two-dimensional (2D) $\mathbb Z_2$ non-trivial isolated mini-bands. To model this…

Mesoscale and Nanoscale Physics · Physics 2024-09-10 Kaijie Yang , Zian Xu , Yanjie Feng , Frank Schindler , Yuanfeng Xu , Zhen Bi , B. Andrei Bernevig , Peizhe Tang , Chao-Xing Liu

We study the topological band theory of time reversal invariant topological insulators and interpret the topological $\mathbb{Z}_2$ invariant as an obstruction in terms of Stiefel--Whitney classes. The band structure of a topological…

Mathematical Physics · Physics 2016-04-12 Ralph M. Kaufmann , Dan Li , Birgit Wehefritz-Kaufmann