Freezing the core: nuclear spintronics at ultra-low temperatures

Research Project, 2021 – 2024

It is well known that the magnetic moment, or the spin of an electron follows the laws of quantummechanics, and it is perhaps the most often studied fundamental two-level system. In solid state materials, where electrons are free to flow, the spin state can couple to the charge current, which in turn can be measured in sensitive experiments at low temperatures.In the same materials, nuclear spins are around thousand times smaller than electron spins and they interact weakly with their environment. While this property is advantageous for long-term quantum information storage, it represents a major technological challenge for their measurement and manipulation. In particular, the effects of the electron spin ordering can be observed at temperatures in the range of one kelvin in nanoscale semiconductors, the same experiment requires less than a millikelvin for nuclear spins. This ultra-cold, microkelvin temperature range in nanoelectronics only became accessible this year by adiabatic demagnetization cooling.Building on this initial demonstration, the goal of this project is to provide the first unambiguous proof of nuclear spin ordering. We will investigate the combined behavior of the electrons and nuclei, which will lead to novel topological states and, via the magnetic-field dependent supercurrent, a coherent long-range coupling between nuclear spin ensembles.