Quantisation of Hopping Magnetoresistance Prefactor in Strongly Correlated Two-Dimensional Electron Systems

We report an universal behaviour of hopping transport in strongly interacting mesoscopic two-dimensional electron systems (2DES). In a certain window of background disorder, the resistivity at low perpendicular magnetic fields follows the expected relation $\rho(B_\perp) = \rho_{\rm{B}}\exp(\alpha B_\perp^2)$\mathrm{.}Theprefactor$\rho_{\rm{B}}$ decreases exponentially with increasing electron density but saturates to a finite value at higher densities. Strikingly, this value is found to be universal when expressed in terms of absolute resistance and and shows quantisation at $R_{\rm{B}}\approx h/e^2$and$R_{\rm{B}}\approx 1/2$ $h\mathrm{/}{e}^2$. We suggest a strongly correlated electronic phase as a possible explanation.