The Joint Condensed Matter Seminar (JCMS) series is organised by KTH Royal Insitute of Technology, Nordita, and Stockholm University.
On Monday, August 31st, 2026 from 10:00 to 11:00 we will host a seminar by Mengjie Yang from National University of Singapore (NUS).
System Size and Structure Change the Physics: Unexpected Transitions in Non-Hermitian Systems
Non-Hermitian systems provide a unique platform where spectral and dynamical properties can be fundamentally different from their Hermitian counterparts. Traditionally, non-Hermitian transitions are controlled by parameters such as gain, loss, and coupling strength. However, the underlying structure and scale of a system can also act as powerful control parameters, leading to unexpected physical phenomena.
This talk explores how connectivity, geometry, system size, and interaction range can reshape non-Hermitian physics. We show that a purely geometric transition through percolation can induce parity-time symmetry breaking by modifying the connectivity of the system. We further demonstrate that changing the transverse structure can reverse non-Hermitian skin accumulation, while increasing the system size can drive a transition from a trivial to a nontrivial topological phase. Finally, we reveal that long-range couplings can fundamentally alter the scaling behavior governing non-Hermitian transitions.
These results establish system structure and scale as active ingredients in controlling nonequilibrium phases, extending the conventional view that phase transitions are determined only by local parameters or external driving.