Professor Erich Krautz-Preisträger 2015: Zhe Wang


Low-dimensional quantum magnets provide unique possibilities to study ground and excited states of quantum models, to explore new phases of quantum matter, and to investigate the interplay of quantum and thermal fluctuations. In his dissertation entitled "Terahertz and Infrared Spectroscopy on Low-Dimensional Quantum Magnets", Zhe Wang has studied quantum phase transitions and quantum spin dynamics, and its interplay with lattice and orbital degrees of freedom, in a variety of low-dimensional quantum spin systems in static and pulsed high magnetic fields up to 60 Tesla.

In Zhe Wang’s award-winning dissertation, the confinement of spinon excitations, as analogue of the concept of quark confinement, is realized and identified in a spin-1/2 Heisenberg-Ising antiferromagnetic chain, which can be described by a one-dimensional Schrödinger equation. By careful measurement of spin excitations in high magnetic fields, quantum phase transitions are revealed. In the spin-1/2 system, a quantum critical phase is induced by a magnetic field, which is characterized by string excitations and fractional spin excitations that emerge above the phase transition. In a spin-1 antiferromagnetic chain, where the Haldane phase is realized as the ground state, Ising- and XY-type antiferromagnetic phases are observed above their respective field-induced quantum phase transitions.