Evidence of Zero-Field Wigner Solids in Ultrathin Films of Cadmium Arsenide

The quantum Wigner crystal is a many-body state where Coulombic repulsion quenches the kinetic energy of electrons, causing them to crystallize into a lattice. Experimental realization of a quantum Wigner crystal at zero magnetic field has been a long-sought goal. Here, we report on the experimental evidence of a Wigner solid in ultra-thin films of cadmium arsenide (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msub><a:mrow><a:mi>Cd</a:mi></a:mrow><a:mn>3</a:mn></a:msub><a:msub><a:mrow><a:mi>As</a:mi></a:mrow><a:mn>2</a:mn></a:msub></a:mrow></a:math>) at zero magnetic field. We show that a finite bias depins the domains and produces an unusually sharp-threshold current-voltage behavior. Hysteresis and voltage fluctuations point to domain motion across the pinning potential and disappear at finite temperature as thermal fluctuations overcome the potential. The application of a small magnetic field destroys the Wigner solid, pointing to an unconventional origin. We use Landau-level spectroscopy to show that the formation of the Wigner solid is closely connected to a topological transition as the film thickness is reduced. Published by the American Physical Society 2024