Superconducting memory and trapped magnetic flux in ternary lanthanum polyhydrides

Abstract: Superconducting memory is a promising technology for data storage because of its speed, high energy efficiency, non-volatility, and compatibility with quantum computing devices. However, the need for cryogenic temperatures makes superconducting memory an extremely expensive and specialized device. Ternary lanthanum polyhydrides, due to their high critical temperatures of 240-250 K, represent a convenient platform for studying effects associated with superconductivity in disordered granular systems. In this work, we investigate a trapped magnetic flux and memory effects in recently discovered lanthanum-neodymium (La,Nd)H${10}$ and lanthanum-scandium (La,Sc)H${12}$ superhydrides at a pressure of 175-196 GPa. We use a steady magnetic field of a few Tesla (T) and strong pulsed fields up to 68 T to create the trapped flux state in the compressed superhydrides. We find a clockwise hysteresis of magnetoresistance in cerium CeH${9-10}$ and lanthanum-cerium (La,Ce)H${10+x}$ polyhydrides, a characteristic feature of granular superconductors. A study of the current-voltage characteristics and voltage-temperature curves of the samples with frozen magnetic flux indicates a significant memory effect in La-Sc polyhydrides already at 225-230 K.