Superconductor-semiconductor hybrid capacitance with a nonlinear charge-voltage profile

Electronic devices that work in the quantum regime often employ hybrid nanostructures to bring about a nonlinear behaviour. The nonlinearity that these can provide has proven to be useful, in particular, for applications in quantum computation. Here we present a hybrid device that acts as a capacitor with a nonlinear charge-voltage relation, similar to the multilayered device studied by Balasubramanian^[1], which can be employed in superconducting circuits.

The device consists of a nanowire placed between the metallic plates of a coplanar capacitor, with a co-parallel alignment. At low temperatures, due to the finite density of states on the nanowire, the charge distribution in the capacitor is uneven and energy-dependent, resulting in a charge-dependent effective capacitance between the metallic plates.

We study this system analytically and numerically, identify working regimes, and show that the nonlinearity of the capacitance can be significant enough to be utilized in circuit quantum electrodynamics. The resulting nonlinearity can be switched on, modulated, and switched off by an external potential, thus making this capacitive device highly versatile for uses in quantum computation.





[1] 2021 J. Phys.: Condens. Matter 33 28LT01