Electromagnetic control of valley splitting in ideal and disordered Si quantum dots

Abstract

In silicon spin qubits, the valley splitting must be tuned far away from the qubit Zeeman splitting to prevent fast qubit relaxation. In this work, we study in detail how the valley splitting depends on the electric and magnetic fields as well as the quantum dot geometry for both ideal and disordered Si/SiGe interfaces. We theoretically model a realistic electrostatically defined quantum dot and find the exact ground and excited states for the out-of-plane electron motion. This enables us to find the electron envelope function and its dependence on the electric and magnetic fields. For a quantum dot with an ideal interface, the slight cyclotron motion of electrons driven by an in-plane magnetic field slightly increases the valley splitting. Importantly, our modeling makes it possible to analyze the effect of arbitrary configurations of interface disorders. In agreement with previous studies, we show that interface steps can significantly reduce the valley splitting. Interestingly, depending on where the interface steps are located, the magnetic field can increase or further suppress the valley splitting. Moreover, the valley splitting can scale linearly or, in the presence of interface steps, non-linearly with the electric field.

13+3 pages, 14 figures

References in corpus (6)

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• Magnetic field dependence of valley splitting in realistic Si/SiGe quantum wells
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• Practical Strategies for Enhancing the Valley Splitting in Si/SiGe Quantum Wells
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• Variability of electron and hole spin qubits due to interface roughness and charge traps
• How valley-orbit states in silicon quantum dots probe quantum well interfaces
• Nonlinear response and crosstalk of electrically driven silicon spin qubits
• Coherent spin-valley oscillations in silicon
• Mapping of valley-splitting by conveyor-mode spin-coherent electron shuttling
• Switching between relaxation hotspots and coldspots in disordered spin qubits
• Interface and electromagnetic effects in the valley splitting of Si quantum dots
• Origin of giant valley splitting in silicon quantum wells induced by superlattice barriers
• Valley-Free Silicon Fins Caused by Shear Strain
• Atomistic compositional details and their importance for spin qubits in isotope-purified silicon-germanium quantum wells
• Valley splitting depending on the size and location of a silicon quantum dot
• Theory of Valley Splitting in Si/SiGe Spin-Qubits: Interplay of Strain, Resonances and Random Alloy Disorder
• Partial Landau-Zener transitions and applications to qubit shuttling
• Theory of Silicon Spin Qubit Relaxation in a Synthetic Spin-Orbit Field
• Modelling of planar germanium hole qubits in electric and magnetic fields
• Proposal for a cavity-induced measurement of the exchange coupling in quantum dots
• Micromagnet-free operation of electron spin qubits in Si/Si${}_{1-x}$Ge${}_x$ vertical double quantum dots
• Towards Utilizing Scanning Gate Microscopy as a High-Resolution Probe of Valley Splitting in Si/SiGe Heterostructures
• Omnidirectional shuttling to avoid valley excitations in Si/SiGe quantum wells
• Interplay of Pauli blockade with electron-photon coupling in quantum dots