Anomalous electric‐field effect and glassy behaviour in granular aluminium: electron glass?

Abstract

Abstract. We present a study of non-equilibrium phenomena observed in the electrical conductance of insulating granular aluminium thin films. An anomalous field effect and its slow relaxation are studied in some detail. The phenomenology is very similar to the one already observed in indium oxide. The origin of the phenomena is discussed. In granular systems, the present experiments can naturally be interpreted along two different lines. One relies on a slow polarisation in the dielectric surrounding the metallic islands. The other one relies on a purely electronic mechanism: the formation of an electron Coulomb glass in the granular metal. More selective experiments and/or quantitative predictions about the Coulomb glass properties are still needed to definitely distinguish between the two scenarii.

Slow relaxation of magnetoresistance in AlGaAs–GaAs quantum well structures quenched in a magnetic field

“…Thus we have discussed two different mechanisms of slow relaxations (of magnetoresistance) in response to time-dependent external magnetic field, both related to the polaron effect. The first one is to some extent similar to the effect of the gate voltage [8,9,10,11,12,13]. It is induced by magnetic-field-driven shift of the chemical potential.…”

“…It worth noting that the slow relaxations in response to variations of the gate voltage are usually not observed in doped crystalline semiconductors -the experiments [8,9,10,11,12,13] were performed using samples with significant amount of disorder. We believe that there two reasons for that: (i) the TLSinduced polaron effects are much weaker that a direct influence of the gate voltage on the DOS; (ii) relatively large sweep rates of the gate voltage probably lead to pronounced nonequilibrium behaviors.…”