Electrons in twisted graphene form novel 1/3 fractional quantum Hall state

A research team discovered a quantum state in which electrons move in a completely new way under a twisted graphene structure. The unique electronic state is expected to contribute to the development of more efficient and faster electronic devices. It may also be applicable to technologies such as quantum memory, which can process complex computations.

Quantum physics is a crucial theory that attempts to understand and explain how atoms and particles interact and move in nature. Such an understanding serves as the basis for designing new technologies that control or utilize nature at the microscopic level. The research conducted holds significance in discovering the quantum state, which is difficult to implement with conventional semiconductor technologies, and in greatly expanding future possibilities for quantum technologies.

Graphene is a material as thin as a piece of paper and is made of carbon atoms. This study utilized a unique structure comprising two slightly twisted layers of graphene, observing a new quantum state. When compared to two transparent films, each film has regular patterns, and when they are rotated slightly, the patterns overlap to reveal new patterns.

The research team revealed that these new patterns create completely different rules for governing the movement of electrons, preventing electrons from crossing from one layer to another while creating strong interactions (Coulomb interactions) between the layers. The paper is published in the journal Nature Communications.

In particular, the research team discovered a new electronic state called “1/3 fractional quantum Hall state.” This state is unique because electrons move as if in three parts, which is completely different from their conventional movement. This state arises from strong interactions between electrons as they push and pull each other between the layers. It was theoretically proven using a Monte Carlo simulation, which demonstrated its physical implications.

Professor Gilyoung Cho at KAIST said, “Our discovery of a fractional quantum Hall state in new materials could contribute significantly to the development of quantum computer technologies.”

Professor Youngwook Kim at DGIST added, “This study is the outcome of close collaboration with NIMS in Japan and the Max Planck Society for the Advancement of Science in Germany. More notably, we used the Max Planck Society’s high-magnetic-field experimental equipment to obtain key data, and our international collaboration opened up new possibilities. We will continue our research to implement similar conditions in an environment where there is no magnetic field.”

This study was led by Youngwook Kim at DGIST and Ph.D. student Seyoung Jin at POSTECH.