Charge and spin topological insulators |
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Authors: | Yu V Kopaev A A Gorbatsevich V I Belyavskii |
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Institution: | 1.Lebedev Physical Institute,Russian Academy of Sciences,Moscow,Russia |
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Abstract: | The topologically nontrivial states of matter—charge and spin topological insulators, which exhibit, respectively, properties
of the integer quantum Hall effect and the quantum spin Hall effect—are discussed. The topological characteristics (invariant
with respect to weak adiabatic changes in the Hamiltonian parameters) which lead to such states are considered. The model
of a 2D hexagonal lattice having symmetries broken with respect to time reversal and spatial inversion which was proposed
by Haldane and marked the beginning of unprecedented activity in the study of topologically nontrivial states is discussed.
This model relates the microscopic nature of the symmetry breaking with respect to the time reversal to the occurrence of
spontaneous orbital currents which circulate within a unit cell. Such currents become zero upon summation over the unit cell,
but they may form spreading current states at the surface which are similar to the edge current states under the quantum Hall
effect. The first model of spontaneous currents (exciton insulator model) is considered, and the possibility of implementing
new topologically nontrivial states in this model is discussed. |
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Keywords: | |
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