68th Annual Meeting of the Austrian Physical Society
Sprache des Tagungstitel:
Charge carriers in semiconductors can have a ?valley? degree of freedom, ?. Limited to discrete
values (like spin), it can be manipulated by applying mechanical strain. This opens the prospect of
valleytronics applications: In addition to the charges, the pseudospin corresponding to a valley?s
population is employed for transporting further information. Most promising is to invoke both,
? and the conventional spin ?. We extend the linear response theory for partially spin-polarized
electron layers to four-fold degenerate spin-valley systems. There, external electric, magnetic,
and mechanical perturbations can independently influence the charge-, spin-, and valley-density, respectively.
Using the Random Phase Approximation (RPA), we derive all partial and cross-correlation re-
sponse functions. Their imaginary parts reflect the possible excitations of the system and show a
rich structure, depending on momentum transfer ?q and energy transfer ??. In particular, we find a
region, where the system is totally non-responsive to applied magnetic fields and mechanical pertur-
bations, similar to the magnetic antiresonance predicted in  for partially spin polarized systems.
 D. Kreil, R. Hobbiger, J.T. Drachta, H.M. Böhm, Physical Review B 92, 205426 (2015)