First-principles analysis of charge transport and spin relaxation in germanium

Germanium is an emerging candidate material for quantum technologies due to its high carrier mobility and strong spin-orbit coupling (SOC). Existing studies of charge transport and spin relaxation in Ge have focused on phenomenological models and qualitative understanding. Leveraging advances in first-principles methods, more quantitative studies of the interactions of carriers and spin with phonons are now possible. In this talk, we present a first-principles study of phonon-limited charge transport and T₁ spin relaxation times in bulk Ge. Our calculations employ an accurate band structure obtained from hybrid functionals and electron-phonon interactions that include SOC via fully-relativistic pseudopotentials. We solve the Boltzmann transport equation to study transport and our recently developed spin-phonon Bethe-Salpeter equation for spin dynamics [1], in both cases using the PERTURBO code [2]. Our computed mobilities and T₁ spin relaxation times are in excellent agreement with experiments in the 100 – 300 K temperature range for both electron and hole carriers. By analyzing the contributions from different phonon modes and electronic valleys, we demonstrate that charge transport and spin relaxation are governed by distinct microscopic mechanisms. The effect of external strain on the mobility and spin relaxation times will also be discussed. Our work sheds light on microscopic electron and spin dynamics in Ge, aiding the development of future Ge-based quantum technologies.