Far-infrared photo-response of 2D electrons in a single InAs/AlGaSb quantum well in the region of EDSR

Motivated by predictions of strong electric dipole spin resonance (EDSR) and possible spin manipulation by electric fields$^{1}$ we have studied the far-infrared (FIR) photo-response of a two-dimensional electron gas (2DEG) in an asymmetric 15\,nm InAs quantum well (Al$_{0.35}$Ga$_{0.65}$Sb barriers). Changes in $R_{xx}$ induced by a FIR laser beam ($E_{FIR}$ = 3.15\,meV) in Hall-bar geometry were measured vs. magnetic field magnitude ($<$10\,T) and tilt angle $\theta$ of the sample normal with a double lock-in technique. We have observed a sharp minimum (20\,mT wide) in a non-resonant background photo-response for $\theta \approx$ 38$^{\circ}$. This line splits into two sharp minima with increasing angle $\theta$ and vanishes for $\theta < 38^{\circ}$. The dip occurs close to the field (odd filling factor $\nu$ = 7) at which we expect EDSR in this highly non-parabolic system. Possible explanations for the splittings will be discussed.\\ $^{1}$E. I. Rashba, Al. L Efros, Appl. Phys. Lett. {\bf{83}}, 5295 (2003).\\ Work supported by DARPA ONR\# N00014-00-1-0951.