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Inequivalence of the low-density insulating state and quantum Hall insulating states in a strongly correlated two-dimensional electron system

M. Yu. Melnikov, D. G. Smirnov, A. A. Shashkin, S. -H. Huang, C. W. Liu, S. V. Kravchenko

Abstract

We find that the behaviors of the voltage-current characteristics as one enters the low-density insulating state and integer quantum Hall insulating states in the ultra-clean two-dimensional electron system in SiGe/Si/SiGe quantum wells are qualitatively different. The double-threshold voltage-current curves, representative of the electron solid formation at low densities, are not observed in the quantum Hall regime, which does not confirm the existence of a quasi-particle quantum Hall Wigner solid and indicates that quasi-particles near integer filling do not form an independent subsystem.

Inequivalence of the low-density insulating state and quantum Hall insulating states in a strongly correlated two-dimensional electron system

Abstract

We find that the behaviors of the voltage-current characteristics as one enters the low-density insulating state and integer quantum Hall insulating states in the ultra-clean two-dimensional electron system in SiGe/Si/SiGe quantum wells are qualitatively different. The double-threshold voltage-current curves, representative of the electron solid formation at low densities, are not observed in the quantum Hall regime, which does not confirm the existence of a quasi-particle quantum Hall Wigner solid and indicates that quasi-particles near integer filling do not form an independent subsystem.

Paper Structure

This paper contains 3 figures.

Figures (3)

  • Figure 1: (a) Magnetoresistivity as a function of electron density at $B=4$ T and $T=30$ mK. The minima of the oscillations are indicated. (b) Voltage-current characteristics at different electron densities in the low-density insulating state at $B=4$ T and $T=30$ mK. The electron densities are indicated in units of $10^{11}$ cm$^{-2}$. Also shown are the dynamic threshold $V_{\text{d}}$ obtained by the extrapolation (dotted line) of the linear part of the $V$-$I$ curves to zero current and the static threshold $V_{\text{s}}$. The dashed lines are fits to the data, see text.
  • Figure 2: (a) The longitudinal voltage as a function of source-drain current at different electron densities in a magnetic field of $B=7$ T and at a temperature of $T=30$ mK for $\nu\leq 1$. The electron densities are indicated in units of $10^{11}$ cm$^{-2}$, along with the filling factors in brackets. (b) Voltage-current characteristics recalculated from the data shown in (a). The inset shows the data on an expanded scale.
  • Figure 3: (a) The longitudinal voltage as a function of source-drain current at different electron densities in a magnetic field of $B=3.5$ T and at a temperature of $T=30$ mK for $\nu\leq 2$. The electron densities are indicated in units of $10^{11}$ cm$^{-2}$, along with the filling factors in brackets. (b) Voltage-current characteristics recalculated from the data shown in (a). The inset shows the data on an expanded scale.