We implement a technique for measuring the singlet-triplet energy splitting responsible for spin-to-charge conversion in semiconductor quantum dots. This method, which requires fast, single-shot charge measurement, reliably extracts an energy in the limits of both large and small splittings. We perform this technique on an undoped, accumulation-mode Si/SiGe triple-quantum dot and find that the measured splitting varies smoothly as a function of confinement gate biases. Not only does this demonstration prove the value of having an insitu excited-state measurement technique as part of a standard tune-up procedure, it also suggests that in typical Si/SiGe quantum dot devices, spin-blockade can be limited by lateral orbital excitation energy rather than valley splitting.
@article{arxiv.1809.08320,
title = {Spin-Blockade Spectroscopy of Si/SiGe Quantum Dots},
author = {A. M. Jones and E. J. Pritchett and E. H. Chen and T. E. Keating and R. W. Andrews and J. Z. Blumoff and L. A. De Lorenzo and K. Eng and S. D. Ha and A. A. Kiselev and S. M. Meenehan and S. T. Merkel and J. A. Wright and L. F. Edge and R. S. Ross and M. T. Rakher and M. G. Borselli and A. Hunter},
journal= {arXiv preprint arXiv:1809.08320},
year = {2019}
}