Master's Defense: Tobias Thornsen Røhling
Gate-Controlled Localization Effects in epitaxially grown InAs Quantum Well
The study of 2-dimensional electron gasses (2DEG) formed in semiconductor quantum wells is a prominent area of research within quantum materials. Among these, epitaxially grown InAs quantum wells stand out due to their exceptionally high carrier mobility, making them highly sought after in the quantum materials community. This thesis investigates the evolution of localization effects in charge carriers within InAs quantum wells, with precise tuning of the 2DEG carrier density via gate voltage. Localization effects were probed by measuring conductance changes as a function of an out-of-plane magnetic field and analysed using the Hikami-Larkin-Nagaoka (HLN) formalism, which models magnetoconductance in 2DEGs with strong spin-orbit coupling. The results demonstrate a gate-controlled transition from weak anti-localization (WAL) to weak localization (WL), with subsequent analysis revealing distinct dependencies of the spin-orbit length and mean free path in these two regimes. Additionally, the temperature dependence of these phenomena was systematically studied, providing further insights into the interplay between quantum interference, spin-orbit coupling, and scattering mechanisms in high-mobility 2DEGs.