Title: A tale from the transverse-field Ising chain to the quantum E8 integrable model

Speaker: Prof. Jianda Wu (吴建达)

Affiliation: Tsung-Dao Lee Institute at Shanghai Jiao Tong University（上海交通大学李政道研究所）

Time: 09:30-11:30, Tuesday, 20th June, 2023 (UTC+8, Beijing Time)

Venue: Room 1502, Yifu Architecture Building, Sipailou Campus of Southeast University, Nanjing

   （东南大学四牌楼校区逸夫建筑馆丘成桐中心1502室）

Inviter: Yunfeng Jiang（江云峰）

Abstract  

Exotic thermodynamics and excitations can emerge in the vicinity of a quantum phase transition. In the talk, I will first detailedly discuss the 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 SrCo2V2O8 [3], we confirm the material 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 first discuss non-trivial low temperature local spin dynamics of the exotic E8 model [5]. Then we show an unambiguous experimental realization of the E8 physics in the material BaCo2V2O8, via nuclear magnetic resonance and inelastic neutron scattering measurements, and detailed theoretical analysis [6 - 9]. 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, various multi-E8-particle states [7, 8] as well as the dispersion of E8 particles [9] in the spin excitation spectrum. Our results open new experimental and theoretical routes 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] J. Wu, L. Zhu & Q. Si, Phys. Rev. B 97, 245127 (2018).

[2] Z. Wang, T. Lorenz, D. I. Gorbunov, P. T. Cong, Y. Kohama, S. Niesen, O. Breunig, J. Engelmayer, A. Herman, J. Wu, K. Kindo, J. Wosnitza, S. Zherlitsyn & A. Loidl, Phys. Rev. Lett. 120, 207205 (2018).

[3] H. Zou, R. Yu & J. Wu, J. Phys.: Condens. Matter. 32, 045602 (2020).

[4] Y. Cui, H. Zou, N. Xi, Z. He, Y. X. Yang, L. Shu, G. H. Zhang, Z. Hu, T. Chen, R. Yu, J. Wu & W. Yu, Phys. Rev. Lett. 123, 067203 (2019).

[5] J. Wu, M. Kormos, Q. Si, Phys. Rev. Lett. 113, 247201 (2014).

[6] X. Wang, H. Zou, K. Hódsági, M. Kormos, G. Takács & J. Wu, Phys. Rev. B 103, 235117 (2021).

[7] Z. Zhang, K. Amelin, X. Wang, H. Zou, J. Yang, U. Nagel, T. Rõõm, T. Dey, A. A. Nugroho, T. Lorenz, J. Wu & Z. Wang, Phys. Rev. B 101, 220411(R) (2020).

[8] H. Zou, Y. Cui, X. Wang, Z. Zhang, J. Yang, G. Xu, A. Okutani, M. Hagiwara, M. Matsuda, G. Wang, G. Mussardo, K. Hódsági, M. Kormos, Z. Z. He, S. Kimura, R. Yu, W. Yu, J. Ma & J. Wu, Phys. Rev. Lett. 127, 077201 (2021).

[9] X. Wang, K. Puzniak, K. Schmalzl, C. Balz, M. Matsuda, A. Okutani, M. Hagiwara, J. Ma, J. Wu, & B. Lake, submitted (2023).

Speaker

Prof. Jianda Wu has long been committed to the research work in quantum phase transitions, quantum critical thermodynamics and dynamics, Bethe ansatz, and dynamics in quantum integrable systems. He obtained BS (2004) and MS (2007) degrees from University of Science and Technology of China, and got PhD (2014) from Rice University. From 2014-2017 he carried out postdoc research at University of California at San Diego, then (2017-2018) became a guest scientist at Max Planck Institute for the Physics of Complex Systems. Since 2018 he became a Tsung-Dao Lee Fellow at Tsung-Dao Lee Institute and a faculty member at School of Physics and Astronomy at Shanghai Jiao Tong University. Prof. Wu has published 29 papers with 10 papers appear on Nature, Nature Physics, Nature Communications, and Phys. Rev. Lett. So far, he has delivered more than 40 invited talks at international conferences/workshops, and universities and institutes around the world.

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。迄今已在包括PRL、Nature及Nature子刊等在内的高水平学术期刊上共发表论文29篇。先后在国际及国内重要学术会议、国内外科研机构及学术单位给邀请学术报告四十余次。