Terahertz quantum Hall effect for spin-split heavy-hole gases in strained Ge quantum wells

Abstract

Spin-split heavy-hole gases in strained germanium quantum wells were characterized by polarisation-resolved terahertz time-domain spectroscopy. Effective masses, carrier densities, g-factors, transport lifetimes, mobilities and Rashba spin-splitting energies were evaluated, giving quantitative insights into the influence of strain. The Rashba coefficient was found to lower for samples with higher biaxial compressive strain, while heavy-hole mobilities were enhanced to over $1.5\times {10}^{6}$ cm ^2 V ^−1 s ^−1 at 3 K. This high mobility enabled the observation of the optical quantum Hall effect at terahertz frequencies for spin-split two-dimensional heavy-holes, evidenced as plateaux in the transverse magnetoconductivity at even and odd filling factors.

Keywords

• terahertz
• quantum Hall effect
• germanium
• spin–orbit
• strain
• quantum well