Topological Insulators

A topological insulator is a material that behaves as an insulator in its interior or bulk while permitting the movement of charges (metallic) on its surface. In the bulk of a topological insulator the electronic band structure resembles an ordinary band insulator, with the Fermi level falling between the conduction and valence bands. On the surface of a topological insulator there are special states that fall within the bulk energy gap and allow surface metallic conduction. Carriers in these surface states have their spin locked at a right-angle to their momentum (spin-momentum locking or topological order). At a given energy the only other available electronic states have opposite spin, so the "U"-turn scattering is strongly suppressed and conduction on the surface is highly metallic. These states are characterized by an index (known as Z2 topological invariants) similar to the genus in topology, and are an example of topologically ordered states.

Some relevant publications: 

• Deep learning for disordered topological insulators through their entanglement spectrum, AJ Uría-Álvarez, D Molpeceres-Mingo, JJ Palacios, Physical Review B 105, 155128 (2022).

• Franckeite as an exfoliable naturally occurring topological insulator, WS Paz, MG Menezes, NN Batista, G Sanchez-Santolino, M Velicky, ... Nano Letters 21, 7781-7788 (2021).

• Laser-Beam-Patterned Topological Insulating States on Thin Semiconducting MoS2, H Mine, A Kobayashi, T Nakamura, T Inoue, S Pakdel, D Marian, ... Physical Review Letters 123 (14), 146803 (2019).

• Topologically protected quantum transport in locally exfoliated bismuth at room temperature,C Sabater, D Gosálbez-Martínez, J Fernández-Rossier, JG Rodrigo, ... Physical Review Letters 110, 176802 (2013).