Emergent linear Rashba spin-orbit coupling offers fast manipulation of hole-spin qubits in germanium

Abstract

The electric dipole spin resonance (EDSR) combining strong spin-orbit coupling (SOC) and electric-dipole transitions facilitates fast spin control in a scalable way, which is the critical aspect of the rapid progress made recently in germanium (Ge) hole-spin qubits. However, a puzzle is raised because centrosymmetric Ge lacks the Dresselhaus SOC, a key element in the initial proposal of the hole-based EDSR. Here, we demonstrate that the recently uncovered finite $k$-linear Rashba SOC of 2D holes offers fast hole-spin control via EDSR with Rabi frequencies in excellent agreement with experimental results over a wide range of driving fields. We also suggest that the Rabi frequency can reach 500 MHz under a higher gate electric field or multiple GHz in a replacement by [110]-oriented quantum wells. These findings bring a deeper understanding for hole-spin qubit manipulation and offer design principles to boost the gate speed.