Séminaire de groupe
|Manipulation of spin in semiconductors: The spin orbit interaction and Berry phases|
|Laboratorio de Física Estadística,Centro de Física, IVIC, Caracas|
|vendredi 11 mai 2007 , 10h25|
|Salle de séminaire du groupe de Physique Statistique|
The lack of inversion symmetry, natural or induced, in semiconductors results in the existence of the coupling between the spin degree of freedom and the electron trajectory. The resulting interaction is both due to a relativistic effect and to the specific band structure of the material which can increase the strength of such coupling by a large factor. We review how this interaction arises and the interesting effects that result in relation to spin relaxation and the mechanical coupling to the lattice due to the angular momentum associated with spin. The talk will then focus on the properties of spin currents by describing their symmetry properties as well as spin-Hall effects, and the possibility of generating such currents by way of strain-induced spin orbit interaction. We find that the spin current mechanism involves the existence of Berry phases in the strain parameter space. The case of protected spin transport (robust to disorder) is a subtle phenomenon that depends on more elaborate topological protection mechanisms similar to those involved in the integer quantum Hall effect.