Engineered valley-orbit splittings in quantum confined nanostructures in silicon

Abstract

An important challenge in silicon quantum electronics in the few electron regime is the potentially small energy gap between the ground and excited orbital states in 3D quantum confined nanostructures due to the multiple valley degeneracies of the conduction band present in silicon. Understanding the "valley-orbit" (VO) gap is essential for silicon qubits, as a large VO gap prevents leakage of the qubit states into a higher dimensional Hilbert space. The VO gap varies considerably depending on quantum confinement, and can be engineered by external electric fields. In this work we investigate VO splitting experimentally and theoretically in a range of confinement regimes. We report measurements of the VO splitting in silicon quantum dot and donor devices through excited state transport spectroscopy. These results are underpinned by large-scale atomistic tight-binding calculations involving over 1 million atoms to compute VO splittings as functions of electric fields, donor depths, and surface disorder. The results provide a comprehensive picture of the range of VO splittings that can be achieved through quantum engineering.

4 pages, 4 figures

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• Intervalley coupling for interface-bound electrons in silicon: An effective mass study
• Spin relaxation in a Si quantum dot due to spin-valley mixing
• Valley splitting of single-electron Si MOS quantum dots
• Detection of a large valley-orbit splitting in silicon with two-donor spectroscopy
• Spatial Metrology of Dopants in Silicon with Exact Lattice Site Precision
• Spin-lattice relaxation times of single donors and donor clusters in silicon
• Electric field reduced charging energies and two-electron bound excited states of single donors in silicon
• Electric-field tuning of the valley splitting in silicon corner dots
• Lifetime enhanced transport in silicon due to spin and valley blockade
• Bounds to electron spin qubit variability for scalable CMOS architectures
• Coherent electrical rotations of valley states in Si quantum dots using the phase of the valley-orbit coupling
• Spatially resolved resonant tunneling on single atoms in silicon
• Electronic properties of delta-doped phosphorus layers in silicon and germanium
• Coherent transfer of singlet-triplet qubit states in an architecture of triple quantum dots
• Resonant tunneling spectroscopy of valley eigenstates on a hybrid double quantum dot
• Valley and spin splittings in PbSe nanowires
• Fast spin-valley-based quantum gates in Si with micromagnets
• Phonon-induced frequency shift in semiconductor spin qubits
• Non-adiabatic quantum control of valley states in silicon