Title: A tale from the transverse-field Ising chain to quantum E8
integrable model
Speaker: Prof. Jianda Wu, Shanghai Jiao Tong University
Time: Jan. 5 (Wensday), 09:00
Venue: Rm M830, IOP-CAS

Abstract:
 Exotic thermodynamics and excitations can emerge in the vicinity of a quantum phase transition. In the talk, I will first detailedly discuss the very unique quantum criticality for the Grüneisen ratio in the transverse field Ising chain (TFIC) [1]. The unique quantum criticality of the Grüneisen ratio then serves as a smoking gun to identify the underlying TFIC universality observed in quasi-1D
antiferromagnetic materials BaCo2V2O8 with transverse field applied along [110] direction [2]. From systematic quantum critical analysis
for the effective model of the material [3], we confirm SrCo2V2O8 with field applied along [100] direction can also accommodate the TFIC
universality with much weaker magnetic field [4]. Furthermore, when the quantum critical point of the TFIC is perturbed by a longitudinal
magnetic field, it was predicted that its massive excitations are precisely described by the exceptional E8 Lie algebra. Here we show an
unambiguous experimental realization of the massive E8 phase in the material BaCo2V2O8, via nuclear magnetic resonance and inelastic
neutron scattering measurements, and detailed theoretical analysis [5, 6, 7]. The large separation between the masked 1D and 3D quantum
critical points of the system allows us to identify, for the first time, the full 8 single-particle E8 excitations as well as various
multi-E8-particle states in the spin excitation spectrum. Our results open new experimental and theoretical route for exploring the dynamics
of quantum integrable systems and physics beyond integrability, and thus bridge key physics in condensed matter and statistical field
theory.

[1] Phys. Rev B 97, 245127 (2018).
[2] Phys. Rev. Lett. 120, 207205 (2018).
[3] J. Phys. Condens. Matter. 32, 045602 (2020).
[4] Phys. Rev. Lett. 123, 067203 (2019).
[5] Phys. Rev. B 101, 220411(R) (2020).
[6] Phys. Rev. B 103, 235117 (2021).
[7] Phys. Rev. Lett. 127, 077201 (2021).


吴建达，李政道学者。长期致力于量子相变、量子临界热力学及动力学、贝特拟设及可积系统动力学等相关领域的研究工作。2004年及2007年于中国科学技术大学获得学士及硕士学位、2014年博士毕业于美国莱斯大学、2014-2017年在美国加州大学圣地亚哥分校从事博士后工作、2017-2018年担任德国马普复杂系统物理所客座研究员。2018年至今就职于上海交通大学李政道研究所及物理与天文学院。2020年入选上海市科委浦江人才计划。迄今共发表论文26篇，包括7篇Physical Review Letters以及Nature、Nature Physics、Nature Communications各一篇。先后在国际学术会议、国内外科研机构及学术单位给特邀学术报告近四十次。