Local control of parity and charge in nanoscale superconducting lead islands

TL;DR

This study investigates how charge and parity states in nanoscale superconducting islands can be controlled and tuned, revealing a crossover between different ground states with potential applications in quantum computing.

Contribution

We experimentally demonstrate control over charge and parity states in superconducting islands using scanning tunneling spectroscopy and voltage pulses, showing tunable ground states.

Findings

Charge quantization observed in small islands

Crossover between even and odd parity states

Tunable superconducting ground states achieved

Abstract

Small superconducting islands can exhibit charge quantization, where Coulomb interactions compete with Cooper pairing. Using scanning tunneling spectroscopy, we probe this interplay by measuring the charging energy ($E_C$) and the pairing energy ($\Delta$) of individual nano-islands. Below a critical island size, where $E_C > \Delta$, we observe a crossover between even and odd parity ground states. By applying controlled voltage pulses, we continuously tune the island's electrostatic potential and map the full charge-parity landscape. These results demonstrate tunable superconducting ground states, offering a potential platform for qubit design and control.