Electrical pulses switch four-layer graphene between magnetic and nonmagnetic states

The samples were made from two slightly misaligned graphene bilayers. Sweeping the gate voltage moved boundaries between regions with the two stacking patterns, producing repeatable switching between a Bernal-dominant state and a mixed rhombohedral-Bernal state. The researchers suggest that the Hall signal may arise at those domain boundaries, but the mechanism has not been settled.

Because the switch physically shifts the layers instead of merely changing the number of charge carriers, the new arrangement can hold without continuous electrical input. Cornell's summary of the work says the team could move back and forth between the configurations consistently.

A low-temperature magnetic effect

The paper reports structural switching that persisted up to room temperature in one device, but the magnetic measurements were much colder. The anomalous Hall effect was characterized at cryogenic temperatures, with reported Curie temperatures ranging from about 2 to 8 kelvins in the measured regions. That distinction matters: the experiment demonstrates electrical control over stacking and low-temperature magnetism, not a practical room-temperature magnetic memory chip.

The result points to a way of controlling quantum phases by rewriting a material's structure with voltage. The researchers say the approach could eventually help create reconfigurable two-dimensional materials or nonvolatile memory, but those applications remain prospective.