Dresden 2020 – wissenschaftliches Programm
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PRV III: Preisträgervortrag
Dienstag, 17. März 2020, 13:15–13:45, HSZ 01
Quantum spin dynamics of a spin-1/2 antiferromagnetic Heisenberg-Ising chain — •Zhe Wang — Institute of Physics II, University of Cologne, Cologne, Germany — Laureate of the Walter Schottky Prize 2020
One-dimensional (1D) spin chains are text-book examples for illustrating basic concepts, such as phase transitions and spin dynamics. Apart from magnon excitations with an integer quantum number, excitations with fractional quantum number (e.g. spinons with S = 1/2) and complex magnon bound states (i.e. Bethe strings) are usually introduced also in the context of spin-chain models. As being exactly solvable, the 1D models provide understanding of the basic concepts in an exact sense, thus it is also a subject of a constant stream of theoretical studies. However, an experimental study of the exotic magnetic excitations is far from straightforward. This is because a proper material realization of the 1D models is scarce, and the magnetic excitations need to be disentangled from other degrees of freedom and at the same time, detectable by available experimental techniques. Recently, these difficulties are overcome in our experimental studies of the spin-1/2 antiferromagnetic Heisenberg-Ising chain compounds SrCo2V2O8 and BaCo2V2O8. I will present our terahertz spectroscopic investigations of quantum spin dynamics in these compounds as a function of temperature and high magnetic fields. In particular, we have been able to identify the long sought-after many-body string excitations, the excitations of confined spinons, as well as magnons, which are characteristic for the different phases connected by magnetic field-induced quantum phase transitions in the 1D spin-1/2 Heisenberg-Ising antiferromagnet.