Absence of localization and large dc conductance in random superlattices with correlated disorder

Abstract

We study how the influence of structural correlations in disordered systems manifests itself in experimentally measurable magnitudes, focusing on dc conductance of semiconductor superlattices with general potential profiles. We show that the existence of bands of extended states in these structures gives rise to very noticeable peaks in the finite temperature dc conductance as the chemical potential is moved through the bands or as the temperature is increased from zero. On the basis of these results we discuss how dc conductance measurements can provide information on the location and width of the bands of extended states. Our predictions can be used to demonstrate experimentally that structural correlations inhibit the localization effects of disorder.

Miniband landscape of disordered dimer superlattices

“…This means that the good transport properties of DSLs are quite independent of the particular realization of the system. This conclusion agrees with our previous claim that the DSL presents high values of the conductance, no matter how the particular arrangement of the DQWs is in each realization ofthe system [19,20]. On the contrary, in the opposite case, when localization effects are strong, the fluctuations are very significant.…”

“…We have investigated numerically the universal quantum fluctuations of the conductance a in a random dimer semiconductor superlattice (DSL) [19]. In this model of disordered superlattice (SL), we consider that the width of the quantum wells takes at random only two values, a and a'.…”

Nature of the eigenstates in the miniband of random dimer-barrier superlattices

“…1 reveals a remarkable feature: the curve of the conductance exhibits a high number of oscillations which are very close together in the regime of high conductance and low concentration and behaves rather smoothly in the band tails of the low conductance. Indeed in agreement with previous reports [28][29][30][31][32][33][34][35][36], in the absence of ensemble averages, the conductance presents several narrow peaks related to the number of the wells in the RDBSL displaying a transmittance close to l. It is apparent that even within the average procedure these peaks are reduced, they are robust enough to survive. This feature indicates the existence of different types of eigenstates: those having a high conductance close to the resonant energy and those with low conductance.…”

“…Such results have been predicted by DominguezAdame, in the last decade, [28][29][30][31][32][33][34][35][36] introducing the correlated structural disorder by means of the so-called random dimer quantum wells superlattices (RDQWSL). In such a case, the resonant tunnelling [27] appears as the principal physical mechanism, breaking down the destructive interference introduced by disorder.…”

Bias driven coherent carrier dynamics in a two-dimensional aperiodic potential

“…[10,11,12,13,14,17,15,16,18] Thus, a short-range correlated disorder was found to stabilize the extended states at special resonance energies. In the thermodynamic limit, such extended states form a set of null measure in the density of states, [10,11,12,13,14] implying the absence of mobility edges in these systems. In contrast, systems with long-range correlations of disorder support a set of delocalized states within a finite bandwidth, [15,16] giving rise to mobility edges.…”