Enhanced spin-orbit coupling in suspended two-dimensional electron gases.

It is already known that spins in the solid state are sensitive to the thermal vibrations in the host lattice that could cause decoherence and low fidelity in any qubit system that is envisaged in a semiconductor device. The work presented here investigates whether a high mobility semiconductor device can be suspended so that the thermal bath is removed, and whether this has any influence on the spin properties of the two-dimensional electron gas. The material of choice is an InGaAs/InAlAs semiconductor heterostructure which has a high Lande spin g-factor. A novel magnetic field modulation technique was used to create ultra-sensitive measurements of the transport properties of a suspended two-dimensional electron gas at low temperatures. In this work it is observed that in the suspended, thermally isolated device the ground state of the electron gas is spin-split due to an enhancement in the spin-orbit effect. The spin-orbit effect lifts the spin degeneracy at zero magnetic field and the strength of this effect is estimated in a suspended InGaAs/InAlAs device. The results of this work show that thermally isolated, spin-orbit coupling enhanced devices can be realised, which is of particular relevance to quantum computing hardware where thermal isolation from the environment is necessary for long coherence times. Additionally, the enhancement in the spin-orbit effect is relevant to electron dipole spin resonance, which facilitates qubit control without the need for on-chip micromagnets or coplanar striplines.