Shot Noise Suppression at Non-integer Conductance Plateaus in a Quantum Point Contact

TL;DR

This study investigates shot noise suppression at both integer and non-integer conductance plateaus in a quantum point contact, revealing electrostatic effects and electron interactions through conductance and noise measurements at low temperature.

Contribution

It demonstrates shot noise suppression at fractional conductance plateaus and highlights the limitations of single-electron models in explaining the 0.7 structure, emphasizing electron-electron interactions.

Findings

Shot noise is highly suppressed at conductance plateaus.

Conductance plateaus evolve to fractional values with increasing voltage.

The 0.7 structure and noise suppression suggest electron-electron interactions.

Abstract

We study non-equilibrium differential conductance and current fluctuations in a single quantum point contact. The two-terminal electrical transport properties -- differential conductance and shot noise -- are measured at 1.5 K as a function of the drain-source voltage and the Schottky split-gate voltage. In differential conductance measurements, conductance plateaus appear at integer multiples of $2e^2/h$ when the drain-source voltage is small, and the plateaus evolve to a fractional of $2e^2/h$ as the drain-source voltage increases. Our shot noise measurements correspondingly show that the shot noise signal is highly suppressed at both the integer and the non-integer conductance plateaus. This main feature can be understood by the induced electrostatic potential model within a single electron picture. In addition, we observe the 0.7 structure in the differential conductance and the suppressed shot noise around 0.7 ($2e^2/h$); however, the previous single-electron model cannot explain the 0.7 structure and the noise suppression, suggesting that this characteristic relates to the electron-electron interactions.