Valley blockade in a silicon double quantum dot

TL;DR

This paper investigates electrical transport in silicon double quantum dots, revealing valley state effects that cause bias asymmetries, and introduces a model based on valley state filling to explain these phenomena.

Contribution

It presents the first detailed measurement of valley-related transport asymmetries in silicon double quantum dots and develops a model explaining these effects through valley state filling.

Findings

Bias triangle asymmetry observed at positive and negative bias.

Evidence suggests valley states, not just spin states, influence tunneling.

A valley state filling model explains the observed transport features.

Abstract

Electrical transport in double quantum dots (DQDs) illuminates many interesting features of the dots' carrier states. Recent advances in silicon quantum information technologies have renewed interest in the valley states of electrons confined in silicon. Here we show measurements of DC transport through a mesa-etched silicon double quantum dot. Comparing bias triangles (i.e., regions of allowed current in DQDs) at positive and negative bias voltages we find a systematic asymmetry in the size of the bias triangles at the two bias polarities. Asymmetries of this nature are associated with blocking of tunneling events due to the occupation of a metastable state. Several features of our data lead us to conclude that the states involved are not simple spin states. Rather, we develop a model based on selective filling of valley states in the DQD that is consistent with all of the qualitative features of our data.