Dynamic self-polarization of the nuclear spins in a GaAs quantum well.

Nuclear spins in a GaAs quantum well achieve self-polarization at ultralow temperatures, reaching as low as 200 nanokelvins, with an Overhauser field of 3.1 tesla.

• Why it matters: Understanding and controlling nuclear spin polarization is crucial for quantum information and spintronics, yet achieving self-polarization at such low temperatures has remained challenging.
• What they did: The study used optical spin pumping and adiabatic demagnetization in a GaAs quantum well, measuring nuclear spin temperatures down to 6.4 microkelvins and observing self-polarization below 500 millikelvins.
• The result: This work demonstrates the realization of dynamic nuclear self-polarization at millikelvin temperatures, enabling new avenues for quantum control and low-temperature spin physics.