Pauli spin blockade and lifetime-enhanced transport in a Si/SiGe double quantum dot

TL;DR

This study investigates spin blockade and lifetime-enhanced transport in a Si/SiGe double quantum dot, demonstrating how long spin relaxation times enable transport through excited states, supported by comprehensive experimental data and detailed modeling.

Contribution

The paper provides the first detailed analysis of lifetime-enhanced transport in Si/SiGe quantum dots, combining experimental data with a comprehensive transport model including tunneling effects.

Findings

Identification of LET as a tail of current when bias exceeds singlet-triplet splitting

Consistent fitting of eight data sets with a unified parameter set

Quantitative estimates of tunneling rates and transport currents

Abstract

We analyze electron transport data through a Si/SiGe double quantum dot in terms of spin blockade and lifetime-enhanced transport (LET), which is transport through excited states that is enabled by long spin relaxation times. We present a series of low-bias voltage measurements showing the sudden appearance of a strong tail of current that we argue is an unambiguous signature of LET appearing when the bias voltage becomes greater than the singlet-triplet splitting for the (2,0) electron state. We present eight independent data sets, four in the forward bias (spin-blockade) regime and four in the reverse bias (lifetime-enhanced transport) regime, and show that all eight data sets can be fit to one consistent set of parameters. We also perform a detailed analysis of the reverse bias (LET) regime, using transport rate equations that include both singlet and triplet transport channels. The model also includes the energy dependent tunneling of electrons across the quantum barriers, and resonant and inelastic tunneling effects. In this way, we obtain excellent fits to the experimental data, and we obtain quantitative estimates for the tunneling rates and transport currents throughout the reverse bias regime. We provide a physical understanding of the different blockade regimes and present detailed predictions for the conditions under which LET may be observed.