Spin-Blockade Spectroscopy of Si/SiGe Quantum Dots

We introduce a technique for measuring the singlet-triplet energy splitting in undoped, accumulation-mode Si/SiGe quantum dots [1]. We find that the measured splitting varies smoothly as a function of confinement gate biases and are also consistent to those obtained using photon-assisted tunneling (PAT) spectroscopy at the (2,0)-(1,1) charge transition. Because our technique operates in the limits of both large and small singlet-triplet energy splittings, we are able to show that the splitting can be limited by the lateral orbital excitation energy rather than solely by the valley splitting in the silicon well.
[1] Jones, A. M., et al. arXiv:1809.08320 (2018).