Study finds how electron crystals melt in phases

Researchers studied how electrons interact on an artificial grid, called a moire lattice, formed by placing two distinct atomically thin materials on top of each other. Because they are on a grid rather than a smooth surface, the electrons can't choose arbitrary locations away from each other, but must fill a point on the grid; the grid constrains how they are arranged.

"When the grid is partially filled, we get to see the impact of their repulsion and how strongly the electrons are interacting with each other," Kim said. "As a result of their interaction, we see that they occupy a regular interval of sites on the lattice, not random intervals."

The particular moire lattice the researchers considered for their study was developed by Cornell experimentalists Kin Fai Mak, professor of physics (A&S) and associate professor of physics in Cornell Engineering, and Jie Shan, professor of physics (A&S) and applied and engineering physics (Engineering).

"Cornell experimentalists are at the frontier of artificial moire material research," Kim said, "doing these amazing experiments with an astonishing degree of control, offering opportunities for theoretical ideas to manifest in physical systems."

Shan and Mak had experimentally detected particular rigid structures that the electrons formed in partially filled grids. Kim and Matty studied how one of these structures would transition to another. They found that when conditions were changed, that very regular, rigid array becomes more fluid.

The researchers identified an intermediate phase between solid and liquid in electrons that has some regularity but not as much as a solid, and not as much freedom as a liquid. They found that the electrons in this state arrange themselves into tiny strips that can move around and orient themselves in structures.

"Electronic liquid crystals had been discussed theoretically, but we're providing a visual image of how they can form microscopically: four or five electrons forming a piece that can be arranged," said Kim. "What we've accomplished is a microscopic understanding of what was only known in principle to be possible." (ANI)