Zu-Jian Ying

Besides exploring novel transition patterns, acquiring a full understanding of the transition nature is an ultimate pursuit in studies of phase transitions. The fundamental models of light-matter interactions manifest single-qubit topological phase transitions (TPTs), which call for an analytical demonstration apart from numerical studies. We present a rigorous study of TPTs in the Jaynes-Cummings model generally with Stark nonlinear coupling.

The superradiant phase transition (SPT) has been widely studied in cavity quantum electrodynamics (CQED). However, this SPT is still subject to ongoing debates due to the no-go theorem induced by the so-called A2 term (AT). We propose a hybrid quantum system, consisting of a single-mode cavity simultaneously coupled to both a two-level system and yttrium-iron-garnet sphere supporting magnons with Kerr nonlinearity, to restore the SPT against the AT.

Abstract As the dimensions of a material shrink from an extended bulk solid to a nanoscale structure, size and quantum confinement effects become dominant, altering the properties of the material. Materials with nanoscale curved geometries, such as rolled-up nanomembranes and zigzag-shaped nanowires, have recently been found to exhibit a number of intriguing electronic and magnetic properties due to shape-driven modifications of charge motion or confinement effects.