Using the CTRW approximation the simplest possible nontrivial model of ac hopping conductivity in disordered solids, is constructed. The model predicts universality of the frequency-dependent conductivity, independent of temperature, chemical composition, and conductivity mechanism, in reasonably good agreement with experiments. It is shown that all qualitative features of experimental ac hoppi...

Conductivity and thermopower measurements of artificial three dimensional bismuth crystals are presented. Due to the size dependent band gap of bismuth, electron transport in the bismuth crystals is a combination of both metallic and hopping conduction. The conductivity and thermopower due to the hopping pathways alone can be extracted through a comparison of the properties of the artificial bi...

Large positive (P) magnetoresistance (MR) has been observed in parallel magnetic fields in a single 2D layer in a delta-doped GaAs/AlGaAs heterostructure with a variable-range-hopping (VRH) mechanism of conductivity. Effect of large PMR is accompanied in strong magnetic fields by a substantial change in the character of the temperature dependence of the conductivity. This implies that spins pla...

Silver vanadate glasses show electrical conductivity higher than 10 S cm, caused by the electron hopping from V to V together with an ionic conduction due to Ag. Lithium vanadate glasses show electrical conductivity of the order of 10 S cm which is primarily due to an electron hopping from V to V. Fraction of the Ag or Li conduction and that of electron hopping from V to V can be estimated by m...

For a system of localised electron states the DC conductivity vanishes at zero temperature, but localised electrons can conduct at finite temperature. Mott gave a theory for the low-temperature conductivity in terms of a variable-range hopping model, which is hard to analyse. Here we give precise asymptotic results for a modified variable-range hopping model, proposed by S. Alexander [Phys. Rev...

The protonic conductivity in the hydrogen bonded chains is investigated theoretically in the framework of the two-stage transport model. The strong interactions with optical phonon stretching mode are considered. We obtain the transition from the insulator to the metal-type state from the temperature dependencies of the hopping conductivity and analyze the influence of the specific Grotthuss me...

The management of proton conductivity in the protic ionic liquid imidazolium bis(trifluoromethylsulfonyl)imide ([Im][TFSI]) is investigated via the use of quasi-elastic neutron scattering (QENS) and pulsed-field gradient NMR. The introduction of excess neutral imidazole to [Im][TFSI] leads to enhanced conductivity. We find that proton dynamics in [Im][TFSI] with excess imidazole are characteriz...

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