Title: String magnetic states: A way toward a unified understanding on 1D and 2D quantum magnetic systems

Speaker: Prof. Jianda Wu (吴建达)

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

Time: 09:30-11:30, Wednesday, 21st 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  

Based on the algebraic Bethe ansatz formalism, we study spin dynamics in the anti-ferromagnetic spin-1/2 XXZ chain with the Ising anisotropy via the form-factor formulae. Various excitations at different energy scales are identified crucial to the dynamic spin structure factors under the guidance of sum rules. At small magnetic polarization, gapless excitations of psinons and antipsinons corresponding to length-1 string (trivial string), dominate the low energy spin dynamics. In contrast, spin dynamics at intermediate and high energies is characterized by the length two- and three-string states. The dynamic spectra of the identified dominant excitations evolve with clear energy separations when tuning the magnetic field, conveying a simple and straightforward way to clearly identify the novel string excitations as well as its dispersions in proper condensed matter systems [1]. Our predictions have been experimentally confirmed on the quasi-one-dimensional material SrCo2V2O8 [2, 3] and BaCo2V2O8 [4]. The concrete progress on string magnetic states further motivates us to develop truncated string state space approach (TS³A) following a simple observation of fast decay of spectra weight in the spin dynamic structure factor with increasing string length [5]. The TS³A then successfully provides a string-state-based unified picture for the spin dynamics observed in different magnetic phase in the material of YbAlO3 whose effective model becomes non-integrable in the magnetic ordering phases [6]. The TS³A we constructed paves down a possible way toward a unified understanding on 1D and 2D quantum magnetic system [5].

[1] W. Yang, J. Wu, S. Xu, Z. Wang, and C. Wu, Phys. Rev. B 100, 184406 (2019).

[2] Z. Wang, J. Wu, W. Yang, A. K. Bera, D. Kamenskyi, S. Xu, A. T. M. N. Islam, B. Lake, C. Wu, and A. Loidl, Nature, 554, 219 (2018).

[3] A. K. Bera, J. Wu, W. Yang, Z. Wang, R. Bewley, M. Boehm, M. Bartkowiak, O. Prokhnenko, B. Klemke, A. T. M. N. Islam, J. M. Law, Bella Lake, Nature Phys. 16, 625 (2020).

[4] Z. Wang, M. Schmidt, A. Loidl, J. Wu, H. Zou, W. Yang, C. Dong, Y. Kohama, K. Kindo, D. I. Gorbunov, S. Niesen, O. Breunig, J. Engelmayer, T. Lorenz, Phys. Rev. Lett. 123, 067202 (2019).

[5] J. Yang and J. Wu, to submit (2023).

[6] J. Yang, T. Xie, S. E. Nikitin, J. Wu, and A. A. Podlesnyak, Accepted by Phys. Rev. B Letter (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。