Fig. 2: Spin relaxation time and valley splitting.
From: Industrial 300 mm wafer processed spin qubits in natural silicon/silicon-germanium
a Measured real time SET current for a spin-up electron (blue) compared to a spin-down electron (orange). b Numerical derivation of the SET current tracking the 1 → 2 electron transition of the qubit dot for external magnetic fields up to 2.5 T. The barrier gate B is used as plunger gate because of the lower lever arm on the dot potential. The change in slope of the tracked transition occurs at the external field, which is equal to the two-electron singlet-triplet splitting. In the regime of strong confinement, this singlet-triplet splitting is almost equal to the valley splitting. Linear fits to the range from 0 T to 0.4 T and 1.3 T to 2.5 T result in a crossing at (0.73 ± 0.08) T which is equal to a valley splitting of (85 ± 9) μeV. c Elzerman pulse sequence for varying waiting times of the loading pulse at an external magnetic field of 0.66 T. The exponential decay corresponds to a spin-relaxation time T1 = (1.09 ± 0.20) s. d Spin relaxation rate 1/T1 over external magnetic field. The black curve shows a fit combining Johnson noise and spin-phonon interaction diverging at the value corresponding to the valley splitting energy. The fit diverges at an external field of (0.76 ± 0.01) T resulting in a valley splitting of (88 ± 1) μeV.
