Topic: Exotic emergences in low-dimensional quantum Ising models.pdf

Speaker:Assoc. Prof. Jianda Wu

Coordinates: PCFT C1124, 16:00, Thursday, March 6

Abstract: When the transverse-field Ising chain (TFIC) at its quantum critical point is perturbed by a longitudinal field along Ising spin direction, it emerges as an integrable model containing eight particles with their scattering matrices and mass spectrum organized by the exceptional $E_8$ Lie algebra. If it weakly couples with the other quantum critical Ising chain but without the longitudinal field, then the weak inter-chain coupling can drive the system to emerge as another integrable model with eight particles, organized by the $D_8^{(1)}$ Lie algebra. Either way, realizing the quantum criticality of the TFIC is a key step to access the two exotic integrable systems. In my talk, I will explore the quantum criticality of the TFIC and its role in identifying materials hosting TFIC quantum criticality and exotic $E_8$ physics. My journey began with an inelastic neutron scattering experiment on ${\mathrm{CoNb}}_2{\mathrm{O}}_6$, sparking my exploration of $E_8$ physics. Despite a ten-year gap, recent THz spectroscopy on the same material reignited my interest, leading us to challenge the $E_8$ paradigm and propose the $D_8^{(1)}$ picture. I will discuss why the $D_8^{(1)}$ physics provides a comprehensive understanding for the experimental observations. Along the course, we also surprisingly found long-life-time dark particle, a special kind of many-body magnetic excitation, in the integrable system which accommodates the $D_8^{(1)}$  physics.