Strongly Nonlinear Superconducting Silicon Resonators

Abstract

Superconducting boron-doped silicon is a promising material for integrated silicon quantum devices. In particular, its low electronic density and moderate disorder make it a suitable candidate for the fabrication of large inductances with low losses at microwave frequencies. We study experimentally the electrodynamics of superconducting silicon thin layers using coplanar waveguide resonators, focusing on the kinetic inductance, the internal losses, and the variation of these quantities with the resonator readout power. We report the observation in a doped semiconductor of microwave resonances with internal quality factors of a few thousand. As expected in the BCS framework, superconducting silicon presents a large sheet kinetic inductance in the 50–500-pH range, comparable to that of strongly disordered superconductors. The temperature dependence of the kinetic inductance is well described by the Mattis-Bardeen theory. However, we find an unexpectedly strong nonlinearity in the complex surface impedance that cannot be satisfactorily explained either by depairing or by quasiparticle heating.

Source-reported materials — not catalogue approval

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