S. S. Safonov

Enhanced Shot Noise in Resonant Tunneling via Interacting Localized States

In a variety of mesoscopic systems shot noise is seen to be suppressed in comparison with its Poisson value. In this work we observe a considerable enhancement of shot noise in the case of resonant tunneling via localized states. We present a model of correlated transport through two localized states which provides both a qualitative and a quantitative description of this effect.

Thermodynamic Density of States of Two-Dimensional GaAs Systems near the Apparent Metal-Insulator Transition

We perform combined resistivity and compressibility studies of two-dimensional hole and electron systems which show the apparent metal-insulator transition - a crossover in the sign of dR/dT with changing density. No thermodynamic anomalies have been detected in the crossover region. Instead, despite a ten-fold difference in r_s, the compressibility of both electrons and holes is well described by the theory of nonlinear screening of the random potential. We show that the resistivity exhibits a scaling behavior near the percolation threshold found from analysis of the compressibility. Notably, the percolation transition occurs at a much lower density than the crossover.

Interactions in 2D electron and hole systems in the intermediate and ballistic regimes

In different 2D semiconductor systems we study the interaction correction to the Drude conductivity in the intermediate and ballistic regimes, where the parameter kBTτ/ changes from 0.1 to 10 (τ is momentum relaxation time). The temperature dependence of the resistance and magnetoresistance in parallel and perpendicular magnetic fields is analysed in terms of the recent theories of electron–electron interactions in systems with different degree of disorder and different character of the fluctuation potential. Generally, good agreement is found between the experiments and the theories.

Suppressed shot noise in 1D and 2D electron transport via localised states

Abstract We have studied shot noise, S I = F 2 eI , in the hopping regime of conduction in small-gate 1D and 2D GaAs transistor structures. It is shown that the Fano factor F in 2D hopping is significantly smaller than that in 1D, which we explain by the difference in the structure of the hopping paths. The Fano factor increases with decreasing sample length, but in all cases does not exceed 0.8. We attribute this behaviour to the presence of the electron–electron interaction.

Shot Noise in Mesoscopic Transport Through Localised States

We show that shot noise can be used for studies of hopping and resonant tunnelling between localised electron states. In hopping via several states, shot noise is seen to be suppressed compared with its classical Poisson value

Thermodynamic and transport properties of 2D GaAs systems near the apparent Metal‐Insulator Transition

S_I=2eI

Interaction effects in high‐mobility two‐dimensional systems

(

Shot noise as a probe of electron dynamics in hopping and resonant tunnelling

I

'Metallic' behaviour of 2D electron and hole systems near the 'metal'-to-'insulator' transition

is the average current) and the suppression depends on the distribution of the barriers between the localised states. In resonant tunnelling through a single impurity an enhancement of shot noise is observed. It has been established, both theoretically and experimentally, that a considerable increase of noise occurs due to Coulomb interaction between two resonant tunnelling channels.

Fermi-liquid behaviour near the crossover from ‘metal’ to ‘insulator’ of 2D electron and hole systems

We have performed combined studies of the charge compressibility and resistance of high‐mobility 2D electron and hole systems in the region where dρ/dT changes its sign with decreasing carrier concentration — the apparent Metal‐Insulator Transition. Despite the large difference in rs, inverse compressibility in both electron and hole systems can be quantitatively explained by a nonlinear screening of disorder by the carriers. In addition, we have shown that the resistance exhibits a scaling characteristic of the percolation transition. The resistance percolation threshold, which agrees with the percolation point obtained from the analysis of the compressibility, is found to be at a lower concentration than the MIT.