M. Z. Hasan

Colloquium : Topological Insulators

Topological insulators are electronic materials that have a bulk band gap like an ordinary insulator but have protected conducting states on their edge or surface. These states are possible due to the combination of spin-orbit interactions and time-reversal symmetry. The two-dimensional (2D) topological insulator is a quantum spin Hall insulator, which is a close cousin of the integer quantum Hall state. A three-dimensional (3D) topological insulator supports novel spin-polarized 2D Dirac fermions on its surface. In this Colloquium the theoretical foundation for topological insulators and superconductors is reviewed and recent experiments are described in which the signatures of topological insulators have been observed. Transport experiments on

Observation of a large-gap topological-insulator class with a single Dirac cone on the surface

\mathrm{Hg}\mathrm{Te}∕\mathrm{Cd}\mathrm{Te}

A topological Dirac insulator in a quantum spin Hall phase

quantum wells are described that demonstrate the existence of the edge states predicted for the quantum spin Hall insulator. Experiments on

A tunable topological insulator in the spin helical Dirac transport regime

{\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x}

Discovery of a Weyl Fermion semimetal and topological Fermi arcs

,

Observation of Unconventional Quantum Spin Textures in Topological Insulators

{\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}

Topological Surface States Protected from Backscattering by Chiral Spin Texture

,

p -type Bi 2 Se 3 for topological insulator and low-temperature thermoelectric applications

{\mathrm{Bi}}_{2}{\mathrm{Te}}_{3}

Development of ferromagnetism in the doped topological insulator Bi 2 − x Mn x Te 3

, and

Observation of a topological crystalline insulator phase and topological phase transition in Pb 1− x Sn x Te

{\mathrm{Sb}}_{2}{\mathrm{Te}}_{3}