Date: 14:30-15:30, Tuesday, 2026/1/13 (13th Jan)
Venue: Rm 401, No. 7 Bld, UCAS Zhongguancun Campus
Speaker: Yunjing Gao (Shanghai Jiao Tong University)
Abstract:
Quantum integrability emerging near a quantum critical point can be manifested by exotic excitations that encode elegant algebraic structures. A well-known example is the observation of E_8 particles in CoNb_2O_6 in 2010. However, a high-resolution THz measurement in 2020 exposes additional peaks beyond E_8 description. Motivated by these, we propose a ladder model consisting of two critical Ising chains with weak interchain coupling to describe the system. Continuum limit of this model was found to be organized by another integrable field theory (IFT) with D_8^{(1)} algebra. Dynamic structure factor is calculated both analytically and numerically, with good agreement obtained between the two approaches and with experimental results. Meanwhile, our analysis shows that not all particles predicted by the IFT are visible through local excitation. To resolve the discrepancy, we carry out systematic study of the Ising ladder model beyond the integrable point. Arising from the interchain coupling confinement, mesonic bound states are identified with different fermion parity and chain-exchanging symmetry. Such characterization explains the particle-selection features in the dynamical spectrum.
About the speaker:
Yunjing Gao is currently a PhD student at Shanghai Jiao Tong University majoring in exact solutions of quantum magnetism in one dimension.
