Pauli Spin Blockade in a Highly Tunable Silicon Double Quantum Dot

TL;DR

This paper demonstrates Pauli spin blockade in a tunable silicon double quantum dot, showing clear spin-dependent transport phenomena and large singlet-triplet splitting, advancing silicon-based quantum computing prospects.

Contribution

The study reports the first clear observation of Pauli spin blockade in a highly tunable silicon double quantum dot with independent control of electron occupancy and tunnel coupling.

Findings

Pauli spin blockade observed at weak inter-dot coupling

Large intra-dot singlet-triplet splitting > 1 meV

Magnetic field dependence of leakage current explained by spin-flip cotunneling

Abstract

Double quantum dots are convenient solid-state platforms to encode quantum information. Two-electron spin states can be conveniently detected and manipulated using strong quantum selection rules based on the Pauli exclusion principle, leading to the well-know Pauli spin blockade of electron transport for triplet states. Coherent spin states would be optimally preserved in an environment free of nuclear spins, which is achievable in silicon by isotopic purification. Here we report on a deliberately engineered, gate-defined silicon metal-oxide-semiconductor double quantum dot system. The electron occupancy of each dot and the inter-dot tunnel coupling are independently tunable by electrostatic gates. At weak inter-dot coupling we clearly observe Pauli spin blockade and measure a large intra-dot singlet-triplet splitting $>$ 1 meV. The leakage current in spin blockade has a peculiar magnetic field dependence, unrelated to electron-nuclear effects and consistent with the effect of spin-flip cotunneling processes. The results obtained here provide excellent prospects for realizing singlet-triplet qubits in silicon.