Quantum Phase Transitions in Clean Ising Superconductors

Superconductivity as a macroscopic quantum state has been intensively studied since its discovery in 1908. Its applications have been significantly broadened, from the high-field coil, and superconducting sensors to quantum information. Especially, the great demand for data processing capability in artificial intelligence has stimulated the vast development in superconductor-based quantum computing. Alongside the engineering application, the understanding of superconductivity has been extended. Exotic superconductivity has been proposed, such as spin-triplet pairing, pair density wave, quantum Griffiths state, and Fulde–Ferrell–Larkin–Ovchinnikov state, which will in turn stimulate the engineering application of superconductivity. This thesis focuses on the quantum phase transitions in two Ising superconductors, the ionic liquid-gated MoS2, and multilayer NbSe2. The Bose-metal-like states and quantum Griffiths states are studied in the ionic liquid-gated MoS2 under perpendicular fields. An unconventional Fulde–Ferrell–Larkin–Ovchinnikov state, induced by coupling of Ising SOC and orbital effect, is studied in multilayer NbSe2 under parallel magnetic fields