Condensed Matter Seminar: Po-Yao Chang, National Tsing Hua University
Entanglement as a Probe of Non-Hermitian Systems and Non-Unitary CFTs
Event Details
- Location: 1080 Physics Research Building
- Faculty Host: Yuan-Ming Lu
Abstract
Entanglement entropy is a key diagnostic for (1+1)D conformal field theories (CFTs), with its scaling directly yielding the central charge. This approach fails for non-unitary CFTs, where central charge can be negative, rendering standard entanglement entropy unphysical. We resolve this by introducing a generalized entanglement entropy, which we validate by correctly extracting negative central charges from models like the PT-symmetric Su-Schrieffer-Heeger model, quantum-group-invariant XXZ model, and the Yang-Lee anyon chain. We then apply this non-Hermitian framework to uncover new physics. We demonstrate that a local non-Hermitian impurity in a critical chain induces an exceptional point that drastically alters the CFT, shifting the central charge from c=1 to c=−2. Furthermore, we discover a PT-symmetric gapless symmetry-protected topological phase that unconventionally hosts robust boundary modes.