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Description
Strain engineering has long been central to semiconductor physics, traditionally used to modify band structures and improve device performance. Recently, it has emerged as an active quantum control parameter, directly coupling to electronic and spin states. In quantum architectures based on compressively strained germanium-on-silicon (cs GoS) technology, both intrinsic and externally applied strain fields are crucial for lifting valence band degeneracy, separating heavy- and light-hole states, and affecting spin–orbit coupling. These strain-induced effects enable rapid, fully electrical and therefore addressable manipulation of hole spin qubits. Recent advances in coherence and tunability of hole spin states have positioned cs GoS material as a very promising platform for scalable hole-based quantum information processing.
In this work, we investigate the interaction between surface acoustic waves (SAWs) and holes confined in gate-defined double quantum dots in cs GoS heterostructures. We combine valence-band theory with COMSOL Multiphysics simulations of acoustic propagation. We find that SAW-induced biaxial strain is the dominant mechanism modulating hole energy levels in this non-piezoelectric system, exceeding displacement-mediated electrostatic effects by more than an order of magnitude under realistic conditions. Exploiting sound-velocity contrast within the heterostructure, we identify hybrid Rayleigh–Sezawa modes whose strain fields are naturally localized at the Ge quantum well containing spin qubits, maximizing phonon–qubit coupling without a need of suspended structures or complex phononic crystals. Furthermore, we show that replacing the piezoelectric layer in the SAW delay line with an acoustically matched non-piezoelectric dielectric preserves high quality of acoustic transmission while minimizing charge noise, enabling purely mechanical strain coupling at the qubit site. For lateral double quantum dots placed at opposite strain phases, SAW excitation yields strong differential modulation of interdot detuning, enabling spin-manipulation gates at tens of gigahertz. This demonstrates SAWs as a route for strain control of hole spin qubits in centrosymmetric group-IV semiconductors within CMOS-compatible architectures.
| Keyword-1 | Strain-Engineering |
|---|---|
| Keyword-2 | Double Quantum Dots |
| Keyword-3 | surface Acoustic Waves |