13 research outputs found
Leakage-current lineshapes from inelastic cotunneling in the Pauli spin blockade regime
We find the leakage current through a double quantum dot in the Pauli spin
blockade regime accounting for inelastic (spin-flip) cotunneling processes.
Taking the energy-dependence of this spin-flip mechanism into account allows
for an accurate description of the current as a function of applied magnetic
fields, gate voltages, and an inter-dot tunnel coupling. In the presence of an
additional local dephasing process or nonuniform magnetic field, we obtain a
simple closed-form analytical expression for the leakage current giving the
full dependence on an applied magnetic field and energy detuning. This work is
important for understanding the nature of leakage, especially in systems where
other spin-flip mechanisms (due, e.g., to hyperfine coupling to nuclear spins
or spin-orbit coupling) are weak, including silicon and carbon-nanotube or
graphene quantum dots.Comment: 11 pages, 10 figures; v2: Typos corrected, colorbar added to fig. 7,
final version published in Phys. Rev.
Stationary and transient leakage current in the Pauli spin blockade
We study the effects of cotunneling and a non-uniform Zeeman splitting on the
stationary and transient leakage current through a double quantum dot in the
Pauli spin blockade regime. We find that the stationary current due to
cotunneling vanishes at low temperature and large applied magnetic field,
allowing for the dynamical preparation of a pure spin ground state, even at
large voltage bias. Additionally, we analyze current that flows between
blocking events, characterized, in general, by a fractional effective charge
. This charge can be used as a sensitive probe of spin relaxation
mechanisms and can be used to determine the visibility of Rabi oscillations.Comment: v1: 4 pages; v2: 4 pages+ additional supplementary material, version
to appear in PR
Pauli Spin Blockade in a Highly Tunable Silicon Double Quantum Dot
Double quantum dots are convenient solid-state platforms to encode quantum information. Two-electron spin states can be detected and manipulated using quantum selection rules based on the Pauli exclusion principle, leading to 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 realising singlet-triplet qubits