Nonlinear Screening Theory of the Coulomb Glass

A nonlinear screening theory is formulated to study the problem of gap formation and its relation to glassy freezing in classical Coulomb glasses. We find that a pseudogap (”plasma dip”) in a single-particle density of states begins to open already at temperatures comparable to the Coulomb energy. This phenomenon is shown to reflect the emergence of short-range correlations in a liquid (plasma) phase, a process which occurs even in the absence of disorder. Glassy ordering emerges when disorder is present, but this occurs only at temperatures roughly an order of magnitude lower. Our result demonstrate that the formation of the plasma dip at high temperatures is a process distinct from the formation of the Efros-Shklovskii pseudogap, which in our model emerges only within the glassy phase.

Figure 1

Our analytical predictions for the single-particle density of states (solid lines) are found to be in excellent quantitative agreement with simulation results (dashed lines), with no adjustable parameters. Shown are results for the three-dimensional case studied in Ref. 7, corresponding to $W=1/(2\sqrt{3})$, and temperatures $T=0.4$, 0.2, 0.1, and 0.05 (top panel), and the two-dimensional model of Ref. 8, corresponding to $W=0$, $T=0.1$, and $K=0.2$. All lines correspond to the plasma phase, while $T=0.05$ is very close to the glass transition temperature.

Figure 2

Three-dimensional Coulomb glass phase diagram. The full horizontal line indicates the RSB instability and the dotted line shows where the RS entropy turns negative. The screening length in the inset is plotted for the same disorder and the range of temperatures (fluid phase) as in Fig. 1.