arXiv subjects

V. M. Pudalov

Publications and source records attributed to V. M. Pudalov.

99 records · Page 6Linked to original sources

arXiv1997

Effect of Tilted Magnetic Field on the Anomalous H=0 Conducting Phase in High-Mobility Si MOSFETs

The suppression by a magnetic field of the anomalous H=0 conducting phase in high-mobility silicon MOSFETs is independent of the angle between the field and the plane of the 2D electron system. In the presence of a parallel field large enough to fully quench the anomalous conducting phase, the behavior is similar to that of disordered GaAs/AlGaAs heterostructures: the system is insulating in zero (perpendicular) field and exhibits reentrant insulator-quantum Hall effect-insulator transitions as a function of perpendicular field. The results demonstrate that the suppression of the low-T phase is related only to the electrons' spin.

cond-mat.str-el↗

arXiv1997

Unconventional Metallic State in Two Dimensional System With Broken Inversion Symmetry

We present a model that explains two phenomena, recently observed in high-mobility Si-MOS structures: (i) the strong enhancement of metallic conduction at low temperatures, T<2 K, and (ii) the occurrence of the metal-insulator transition in 2D electron system. Both effects are prescribed to the Coulomb and spin-orbit interaction; the latter is anomalously enhanced by the broken inversion symmetry of the confining potential well.

cond-mat.str-el↗

arXiv1997

On the Origin of the Metal-Insulator Transition in 2D

Two phenomena have been recently observed in high-mobility Si MOS structures: (1) strong enhancement of the metallic conduction at low temperatures, T < 2K, and (2) the scaling behavior of the temperature and electric field dependences of the resistivity. These results evidence for the true metal-insulator transition in 2d, in apparent disagreement with the one-parameter scaling theory. Here we present a model that explains both effects in the framework of the spin-orbit interaction and provides a quantitative agreement with the experimental data.

cond-mat.str-el↗

arXiv1997

Instability of the Two-Dimensional Metallic Phase to Parallel Magnetic Field

We report on magnetotransport studies of the unusual two-dimensional metallic phase in high mobility Si-MOS structures. We have observed that the magnetic field applied in the 2D plane suppresses the metallic state, causing the resistivity to increase dramatically by more than 30 times. Over the total existence range of the metallic state, we have found three distinct types of the magnetoresistance, related to the corresponding quantum corrections to the conductivity. Our data suggest that the unusual metallic state is a consequence of both spin- and Coulomb-interaction effects.

cond-mat.str-el↗

arXiv1995

Global phase diagram for the quantum Hall effect: An experimental picture

We study the behavior of the extended states of a two-dimensional electron system in silicon in a magnetic field, B. Our results show that the extended states, corresponding to the centers of different Landau levels, merge with the lowest extended state as B --> 0. Using our data, we construct an experimental-based ``disorder vs filling factor'' phase diagram for the integer quantum Hall effect (QHE). Generalizing this diagram to the case of the fractional QHE, we show that it is consistent with the recently observed direct transitions between insulator and FQHE at 2/5, 2/7, and 2/9.

cond-mat↗

arXiv1995

DESTRUCTION OF THE QUANTUM HALL EFFECT WITH INCREASING DISORDER

We report experimental studies of disorder-induced transitions between quantum-Hall, metallic, and insulating states in a very dilute two-dimensional electron system in silicon at a magnetic field corresponding to Landau level filling factor $ν=1$. At low disorder, the lowest extended state at $ν=1$ is below the Fermi energy so that the system is in the quantum Hall state. Our data show that with increasing disorder (but at constant electron density and magnetic field), the extended state DOES NOT DISAPPEAR BUT FLOATS UP IN ENERGY SO THAT THE SYSTEM BECOMES INSULATING. As the extended state crosses the Fermi energy, the conductivity $σ_{xx}\sim e^2/2h$ has temperature dependence characteristic of a metallic system.

cond-mat↗

arXiv1994

"Scaling of an anomalous metal/insulator transition in a 2D system in silicon at zero magnetic field"

We have studied the temperature dependence of resistivity, $ρ$, for a two-dimensional electron system in silicon at low electron densities, $n_s\sim10^{11}$ cm$^{-2}$, near the metal/insulator transition. The resistivity was empirically found to scale with a single parameter, $T_0$, which approaches zero at some critical electron density, $n_c$, and increases as a power $T_0\propto|n_s-n_c|^β$ with $β=1.6\pm0.1$ both in metallic ($n_s>n_c$) and insulating ($n_s<n_c$) regions. This dependence was found to be sample-independent. We have also studied the diagonal resistivity at Landau level filling factor $ν=3/2$ where the system is known to be in a metallic state at high magnetic field and in an insulating state at low magnetic field. The temperature dependencies of resistivity at $B=0$ and at $ν=3/2$ were found to be identical. These behaviors suggest a true metal/insulator transition in the two dimensional electron system in silicon at $B=0$, in contrast with the well-known scaling theory.

cond-mat↗

arXiv1994

Temperature Induced Transitions between Insulator, Metal, and Quantum Hall States

We report the observation of TEMPERATURE-INDUCED transitions between insulator, metal, and quantum-Hall behaviors for transport coefficients in the very dilute high mobility two-dimensional electron system in silicon. We consider the $ν=1$ quantum Hall effect at the border of it's existence, at very low electron density. Our data show that as the temperature decreases, the extended states at $ν=1$ (above the Fermi level at higher temperature so that the system behaves as an insulator) sink below the Fermi energy, so that the quantum Hall effect occurs. As the extended states cross the Fermi level, the conductivity has a temperature dependence characteristic of a metallic system.

cond-mat↗

arXiv1994

Possible Metal/Insulator Transition at B=0 in Two Dimensions

We have studied the zero magnetic field resistivity of unique high- mobility two-dimensional electron system in silicon. At very low electron density (but higher than some sample-dependent critical value, $n_{cr}\sim 10^{11}$ cm$^{-2}$), CONVENTIONAL WEAK LOCALIZATION IS OVERPOWERED BY A SHARP DROP OF RESISTIVITY BY AN ORDER OF MAGNITUDE with decreasing temperature below 1--2 K. No further evidence for electron localization is seen down to at least 20 mK. For $n_s<N_{cr}$, the sample is insulating. The resistivity is empirically found to SCALE WITH TEMPERATURE BOTH BELOW AND ABOVE $n_{cr}$ WITH A SINGLE PARAMETER which approaches zero at $n_s=n_{cr}$ suggesting a metal/ insulator phase transition.

cond-mat↗