Low-band-gap materials

Spin-orbit interaction scales inversely with the band-gap of the semiconductor. This makes narrow-gap materials like InAs, GaSb and InSb interesting for applications like helical modes in quantum spin-Hall devices or Majorana Fermions in semiconductor nanowires.

We have extended our optical pump-probe method to the infrared range to investigate spin dynamics and spin orbit interaction in such materials [1].


[1] T. Henn, L. Czornomaz and G. Salis, “Characterization of spin-orbit fields in InGaAs quantum wells,” Appl. Phys. Lett. 109, 152104 (2016).

Spatial maps of spin polarization

(a) Spin precession measured at room temperature in an In0.53Ga0.47As quantum well in a magnetic field of 1 T, taken at different overlap positions between excitation and detection spots. (b) The excited spin polarization has a Gaussian shape that is given by the laser intensity profile. (c) Spin diffusion along different spatial directions are probed by displacing the probe beam position with respect to the pump beam, leading to spin-orbit induced changes of the spin precession frequency.