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Terahertz Spectroscopy of Quantum Spin Dynamics in Low-Dimensional Quantum Magnets

Date: 2018-12-19
Time: 10:00
Venue: M253
Speaker: Dr. Zhe Wang

Helmholtz-Center Dresden-Rossendorf, Dresden, Germany 


Quantum states in low-dimensional spin systems are characterized by their characteristic spin dynamics. In this seminar, I will talk about our recent works on terahertz spectroscopy of quantum spin dynamics in low-dimensional quantum magnets, such as quantum spin dimer, quantum spin chain, and two-dimensional frustrated magnet. I will briefly introduce how spin excitations in a spin system could be probed and magnetic interactions be determined by terahertz spectroscopy [1]. The main focus of the seminar will be on dynamics of a spin-1/2 Heisenberg-Ising antiferromagnetic chain for longitudinal and transverse magnetic fields [2–5]. In addition to the well-known low-energy spin dynamics, I will show that high-energy excitations, such as confined spinons [2] and Bethe strings [3], are realized in the spin chain system for a longitudinal field. Moreover, in a transverse field, our study of spin dynamics allowed us to identify a quantum critical point of the transverse-field Ising-chain [4,5]. The experimental results are very well compared to theoretical calculations, as the spin chain model is exactly solvable [6,7]. In addition, spin dynamics in α-RuCl3, a candidate for realizing quantum spin liquid, will be discussed [8].


[1] ZW et al. Phys. Rev. B 89, 174406 (2014).
[2] ZW et al. Phys. Rev. B 91, 140404(R) (2015).
[3] ZW et al. Nature 554, 219–223 (2018).
[4] ZW et al. Phys. Rev. B 94, 125130 (2016).
[5] ZW et al. Phys. Rev. Lett. 120, 207205 (2018).
[6] Wang Yang et al. arXiv:1702.01854 (2017)
[7] Jianda Wu et al. Phys. Rev. B 97, 245127 (2018).
[8] ZW et al, Phys. Rev. Lett. 119, 227202 (2017).

Brief CV of Dr. Zhe Wang

Dr. Zhe Wang studied physics in Nanjing Universtity, and obtained his master (2010) and doctor degrees (2015) at the University of Augsburg, Germany. Since 2017, he has been a director’s postdoctoral fellow in the Helmholtz-Center Dresden-Rossendorf, Germany. His research focuses on linear and nonlinear terahertz spectroscopy of condensed matter, particularly on quantum magnetism, unconventional superconductivity, and multiferroics.