Even Denominator Fractional Quantum Hall States in Graphene

Published January 29, 2019

$Penetration field capacitance (CP) plotted vs magnetic field (B) and electron density (n0) showing both new and well studied fractional quantum Hall states, which appear as orange and red lines.$

Penetration field capacitance (CP) plotted vs magnetic field (B) and electron density (n0) showing both new and well studied fractional quantum Hall states, which appear as orange and red lines.

Scientists revealed previously unobserved and unexpected FQH states in monolayer graphene that raise new questions regarding the interaction between electrons in these states.

What did scientists discover?

Fractional quantum Hall (FQH) states are topological, insulating states in which the electron-electron interaction results in a quasiparticle that behaves as if it only has a fraction of the charge normally carried by a free electron. In a single layer of graphene, scientists observed a new and unexpected class of FQH states that occur within a narrow range of magnetic fields around 28 teslas.

Why is this important?

FQH states are one of the most striking effects of electron interactions. Some exhibit properties that could be exploited for quantum computation. This discovery showcases the potential for engineering new properties by tuning, or manipulating, graphene using electric and magnetic fields.

Who did the research?

A. A. Zibrov¹, E.M. Spanton¹, H. Zhou¹, C. Kometter¹, T. Taniguchi², K. Watanabe², A.F. Young¹

¹University of California, Santa Barbara; ²National Institute for Materials Science

Why did they need the MagLab?

In many samples, the new FQH states only occur for a narrow range of high magnetic fields, up to 30 tesla. Additionally, temperatures below 1 kelvin are required to observe the most fragile of these quantum mechanical states.