Dr. Zhe Wang at ISSP

On the occasion of the 16th International Conference on Megagauss Magnetic Field Generation and Related Topics (MG-XVI), from mid-September to mid-October 2018, I was invited by Prof. Yoshimitsu Kohama to visit the Institute for Solid State Physics, the University of Tokyo, to carry out collaborative projects on quantum magnetism.

Low-dimensional quantum spin systems provide enlightening understanding of many fundamental concepts, such as fractionalized spin excitation and field-induced quantum phase transition. Since a field-induced quantum phase transition usually corresponds to spin-gap closing at a critical field, it is a relatively straightforward way to measure the elementary spin excitations as a function of the applied magnetic field, in order to characterize the quantum phase transition. To do so, the typical methodology that I have adopted to utilize is terahertz optical spectroscopy. Low-energy spin dynamics in various low-dimensional spin systems has been probed crossing the field-induced phase transition.

Complementary to the electrodynamic approach, crucial information about a quantum phase transition can be provided by thermodynamic probes, such as magnetization and magnetocaloric-effect. With Kohama-san, we have studied quantum critical properties in the spin-chain material BaCo₂V₂O₈ using a technique for magnetocaloric-effect measurements in pulsed magnetic fields, which he has established at ISSP. These measurements provide appealing evidence for realization of the quantum phase transition of the paradigmatic spin model of transverse-field Ising-chain. Ongoing collaborations aim at studying how the quantum phase transition could be tuned by chemical doping, and also on another representative class of quantum magnets – quantum spin-dimer systems, which are hosts of magnonic Bose-Einstein condensate.

Yoshimitsu Kohama, Zhe Wang, Chao Dong (right to left）

I am very grateful for the opportunity to visit ISSP. It has been a very pleasant research stay. Besides the successful experiments, I have enjoyed extensive discussions with the local scientists and other visiting scholars. I hope to visit ISSP again in the future.

Zhe, Wang
Helmholtz Zentrum Dresden Rossendorf