Electrostatic-controlled parity switching in InAs-Al hybrid Coulomb island without Zeeman effect

The ground-state parity in superconductor-semiconductor hybrid systems indeed plays a pivotal role in both the pursuit of Majorana zero modes (MZMs) and the development of topological qubits. Here, we report the gate control of a ground-state parity switch in an InAs-Al hybrid nanowire Coulomb island without the Zeeman effect. The evolution in Coulomb-blockaded spectroscopy reveals a gate-driven crossing of a subgap state through zero energy, revealing characteristics of a spin-polarized Andreev bound state (ABS). Our findings indicate the presence of spin splitting without a Zeeman field and demonstrate the potential for parity manipulation via purely electrostatic control and modulation.