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 cm2 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.
Highlights
The spin–orbit interaction (SOI) gives rise to fascinating physical phenomena, and offers potential application in spintronic devices as it can lift spin degeneracy even at zero external magnetic field [1]
In Ge quantum wells with Si1-xGex buffer layers the degeneracy of the heavy hole (HH) and light hole (LH) valence bands is lifted by strain, giving an energy difference EHH,LH = ∣EHH - ELH∣ at zero wavevector [9, 10], and making HHs lighter
As opposed to the k-linear Rashba SOI experienced by conduction band electrons and LHs, for HHs the Rashba SOI
Summary
M Failla, J Keller, G Scalari, C Maissen, J Faist, C Reichl, W Wegscheider, O J Newell, D R Leadley, M Myronov and J Lloyd-Hughes.
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