Anisotropic disordered Wigner solid in a two-dimensional electron system

In a two-dimensional electron system, when Coulomb energy dominates over the kinetic energy, electrons should freeze into an ordered array known as Wigner solid. Its realization is challenging as it requires simultaneous low-density and high-quality. Here, we report transport measurements in a clean (low-disorder) two-dimensional electron system with anisotropic effective mass and Fermi sea. The data reveal that at extremely low electron densities, when the r_s parameter, the ratio of the Coulomb to the Fermi energy, exceeds 38, the current-voltage characteristics become strongly nonlinear at small DC biases [1]. Several features of the nonlinear characteristics, including the voltage thresholds, are consistent with the formation of a Wigner solid pinned by the ubiquitous disorder potential. Notably, our data show the transference of effective mass anisotropy of the Fermi liquid to the pinned Wigner solid: we observe anisotropic resistance, activation gap, and de-pinning voltage in the Wigner solid phase. These observations point to an elusive state of matter, namely anisotropic Wigner solid.

[1]. Md. S. Hossain, M. K. Ma, K. A. Villegas-Rosales, Y. J. Chung, L. N. Pfeiffer, K. W. West, K. W. Baldwin, and M. Shayegan, Phys. Rev. Lett. 129, 036601 (2022).