A New Memory Effect in Bulk Crystals of 1T-TaS₂

Strongly correlated systems famously show intriguing (and unexpected) phenomena. The layered 1T-TaS₂ is no exception, showing different charge density wave configurations, metal insulator transitions (MITs), a fascinating superconducting phase, and low-temperature meta-stable hidden phases upon light or current pulses. And now – also a non-volatile memory effect. The memory forms following cooling of the sample to a chosen temperature in the metal-insulator coexisting phase of the Mott MIT (≈180 K) then ramping back up to the metallic state. It manifests as a resistance decrease in the following R versus T measurement that is largest at the ramp-reversal temperature. The memory disappears after cooling to lower temperatures and the original R versus T is recovered. Memory properties are shown to coincide with those of the ramp reversal memory (RRM) previously reported in correlated oxides, including non-volatility and the ability to write more than one memory. However, there are notable differences and a different origin. These findings indicate that RRM extends beyond oxides, highlighting its universality in correlated materials having the necessary ingredients: phase transition with spatial phase coexistence and a mechanism that locally modifies the transition properties. These findings open new opportunities for exploring memory phenomena in correlated materials.