Condensed Matter Physics Seminar
Event Details:
Place: Gant Building, Physics Wing, room GS117
Time: Wednesday, February 23rd, 2:00 PM
“Order parameter steering by light”
Dr. Zhiyuan Sun, Harvard University
An emerging subject in nonequilibrium physics is“order parameter steering”where experimentally controllable perturbations (such as light pulses) may drive the order parameters of symmetry broken phases to evolve. I will theoretically demonstrate this phenomenon in two categories: mean field steering and fluctuation steering. In the first category, we show that in excitonic insulators with s-wave electron-hole pairing, an applied light pulse can induce a p-wave component to the order parameter, and further drive it to rotate in the s+ip plane. In one dimension, each cycle of rotation pumps exactly two electrons across the sample while higher dimensional systems are similar, realizing a Thouless charge pump as a collective manybody effect. In the fluctuation steering category, we study the dynamics of a competing order system which is rapidly heated up by a pump and then cools down. In the cooling process, exponentially growing thermal fluctuations lead the system into the phase associated with the faster-relaxing order parameter, which is not necessarily the ground state. This theory offers a natural explanation for the widespread experimental observation that metastable states may be induced by laser induced collapse of a dominant order.
For more information, contact: Jack Potter / Physics at jack.potter@uconn.edu