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[38] [39] The surface states of a 3D topological insulator is a new type of two-dimensional electron gas (2DEG) where the electron's spin is locked to its linear momentum. [31] Fully bulk-insulating or intrinsic 3D topological insulator states exist in Bi-based materials as demonstrated in surface transport measurements. [40]
It indicates the mathematical group for the topological invariant of the topological insulators and topological superconductors, given a dimension and discrete symmetry class. [1] The ten possible discrete symmetry families are classified according to three main symmetries: particle-hole symmetry, time-reversal symmetry and chiral symmetry.
Two-dimensional topological insulators (also known as the quantum spin Hall insulators) with one-dimensional helical edge states were predicted in 2006 by Bernevig, Hughes and Zhang to occur in quantum wells (very thin layers) of mercury telluride sandwiched between cadmium telluride, [7] and were observed in 2007.
Topological plexcitons make use of the properties of TIs to achieve similar control over the direction of current flow. [3] Plexcitons were found to emerge from an organic molecular layer (excitons) and a metallic film (plasmons). Dirac cones appeared in the plexcitons' two-dimensional band-structure. An external magnetic field created a gap ...
[2] But in the case where the spacing between the hydrogen atoms is gradually increased, at some point the chain must become an insulator. Expressed using the Hubbard model, the Hamiltonian is made up of two terms. The first term describes the kinetic energy of the system, parameterized by the hopping integral, .
Typical examples include graphene, topological insulators, bismuth antimony thin films and some other novel nanomaterials, [1] [4] [5] in which the electronic energy and momentum have a linear dispersion relation such that the electronic band structure near the Fermi level takes the shape of an upper conical surface for the electrons and a ...
Schematic picture of energy levels and examples of different states. Discrete spectrum states [nb 1] (green), resonant states (blue dotted line) [1] and bound states in the continuum (red). Partially reproduced from [2] and [3] A bound state in the continuum (BIC) is an eigenstate of some particular quantum system with the following properties:
In certain materials the topological invariant can be changed when certain bulk energy bands invert due to strong spin-orbital coupling. At the interface between an insulator with non-trivial topology, a so-called topological insulator, and one with a trivial topology, the interface must become metallic.