Thursday, July 18, 2013

1307.4441 (Andrew Das Arulsamy)

Time-reversal operation and transport phenomena in topological

Andrew Das Arulsamy
We explore the time reversal operation properly to show that a static electric current produces `external' magnetic field such that it violates the time reversal symmetry (TRS). Therefore, any forms of electric current measurements (with or without applied magnetic field) within a gapped or gapless quantum system necessarily violate TRS. We then use the ionization energy theory to unequivocally show that the metallic surface states of a topological insulator consist of some `special' energy level crossings (in momentum space), and precisely at each of these crossing points, the energy levels are degenerate, not due to Kramers degeneracy because there is a finite energy gap due to different wavefunctions. This special energy gap is nonzero (xi \neq 0) even when the band (E_g = 0) and Mott-Hubbard (U_H = 0) gaps are zero. We use xi \neq 0 to derive the electron-ion scattering strength required to explain the transport properties of topological insulators for different chemical compositions. We critically comment on our theory and its predictions with respect to recent experimental data.
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