Coherent electrical control of single high spin nucleus
December 5, 2018 @ 3:00 pm
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For over 7 decades, nuclear magnetic resonance (NMR) has been the prime mechanism to access nuclear spins in matter, enabling wonderful techniques such as MRI scanners. However, soon after its discovery, key researchers in the field started investigating more subtle effects observed in NMR spectra originating from the nuclear quadrupole interaction present in nuclei with spins larger than 1/2. This lead Bloembergen to predict in 1961 that time-varying electric fields should cause nuclear electric resonance (NER) by modulating the nuclear quadrupole interaction strength. The underlying mechanism got known as the ‘linear quadrupole Stark effect’: an external electric field changes the polarization of the covalent bonds connecting the atom of interest to the rest of the lattice or molecule, and this results in a changing electric field gradient (and therefore nuclear quadrupole interaction strength) at the nucleus. This effect was subsequently observed and studied spectroscopically in bulk samples. In this talk I will show how we found this effect in our single 123-Sb donor device, and demonstrate, for the fist time, coherent, purely electrical control of a single high spin nucleus. I will share our current theoretical understanding of the microscopic mechanism at play in our device, based on analytical approximations from the sixties and density functional theory calculations. Interestingly, this find was not anticipated, but a true discovery enabled by a broken high frequency control line. These results therefore serve as a reminder to always expect the unexpected, and to never give up on trying to understand interesting odd data.