The Coulomb gap and low energy statistics for Coulomb glasses
We study the statistics of local energy minima in the configuration space of two-dimensional lattice Coulomb glasses with site disorder and the behavior of the Coulomb gap depending on the strength of random site energies. At intermediate disorder, i.e., when the typical strength of the disorder is of the same order as the nearest-neighbor Coulomb energy, the high energy tail of the distribution of the local minima is exponential. We furthermore analyze the structure of the local minima and show that most sites of the system have the same occupation numbers in all of these states. The density of states (DOS) shows a transition from the crystalline state at zero disorder (with a hard gap) to an intermediate, probably glassy state with a Coulomb gap. We analyze this Coulomb gap in some detail and show that the DOS deviates slightly from the traditional linear behavior in 2D. For finite systems these intermediate Coulomb gap states disappear for large disorder strengths and only a random localized state in which all electrons are in the minima of the random potential exists. Dedication: This paper is dedicated to Thomas Nattermann, our dearest friend, brilliant colleague, and outstanding teacher.
Suppressed density of states in self-generated Coulomb glasses
We investigate the structure of metastable states in self-generated Coulomb glasses. In dramatic contrast to disordered electron glasses, we find that these states lack marginal stability. Such absence of marginal stability is reflected by the suppression of the single-particle density of states into an exponentially soft gap of the form g ( ϵ ) ∼ e − V / ξ ∣ ϵ ∣ . To analytically explain this behavior, we extend the stability criterion of Efros and Shklovskii to incorporate local charge correlations, in qualitative agreement with our numerical findings. Our work suggests the existence of a new class of self-generated glasses dominated by strong geometric frustration.
Coulomb gap in a disordered semiconductor
Conditions of the Coulomb gap to appear in the energy spectrum of a disordered semiconductor are studied avoiding assumptions too model-like. In particular the form of the electron-electron interaction potential is not specified, up to the assumption that it is screened in some way. Low temperature screening, absorption of low-frequency electromagnetic waves, and some thermodynamic properties are considered for a system containing a “soft” density of states gap. 
 
 
 
Bedingungen fur das Auftreten einer Coulomblucke im Energiespektrum eines fehlgeordneten Halbleiters werden untersucht, wobei zu modellahnliche Annahmen vermieden werden. Ins besondere wird die Form der Elektron-Elektron-Wechselwirkung nicht festgelegt, bis auf die Annahme, das sie in irgendeiner Weise abgeschirmt ist. Tieftemperaturabschirmung, Absorption von niederfrequenten elektromagnetischen Wellen und einige thermodynamische Eigenschaften werden fur ein System mit „weicher” Zustandsdichtelucke betrachtet.