Nanowerk April 10, 2024
A variety of two-dimensional systems have shown evidence for Wigner crystals (WCs), electrons crystallized into a closely packed lattice. However, a spontaneously formed classical or quantum WC has never been directly visualized. An international team of researchers (USA – Princeton University, UC Berkeley, Lawrence Berkeley National Laboratory, Japan) imaged a magnetic-field-induced electron WC in Bernal-stacked bilayer graphene and examined its structural properties as a function of electron density, magnetic field, and temperature. At high fields and the lowest temperature, they observed a triangular lattice electron WC in the lowest Landau level. The WC possessed the expected lattice constant and was robust between filling except near fillings where it competed with fractional quantum Hall states. Increasing the density or temperature resulted in the melting of the WC into a liquid phase but had a modulated structure. At low magnetic fields, the WC unexpectedly transitioned into an anisotropic stripe phase. Analysis of individual lattice sites showed signatures that might be related to the quantum zero-point motion of electrons in the WC lattice… read more. TECHNICAL ARTICLE
Emergent triangular lattice at partial filling of a N = 0 Landau level in BLG… Credit: Nature volume 628, pages287–292, 10 April 2024