Topology refers to the overall property that remains unchanged despite continuous local modifications. A coffee cup is no different from a donut in the view of mathematicians because they have the same topological charge. Materials with various topological charges display diverse properties. Exploring phase transitions between different topological states brings prospects for novel materials and new physics.
Recently, a research team led by Prof. DU Jiangfeng, Prof. LIN Yiheng, and Prof. LUO Xiwang from the University of Science and Technology of China (USTC) of the Chinese Academy of Sciences (CAS) experimentally observed the phase transitions between triply degenerate points (TDPs) with different topological charges through highly controllable quantum simulations. The study was published in Physical Review Letters.
The researchers performed quantum simulations of topological phase transitions between TDPs in fermionic systems. Through a three-level trapped Be-+ ion driven by ratio frequency and microwave fields, a spin-1 quantum state was obtained. By tuning spin-tensor-momentum coupling strengths, they observed the topological phase transitions of the quantum states and illuminated the important roles played by the spin tensors.
During the construction of the multilevel trapped ion systems, the researchers developed various techniques to study high-spin physics. They prolonged coherence time by an order of magnitude via dynamical decoupling. Besides, they realized swift quantum control techniques on a four-level trapped ion system through analytical models. These efforts laid the foundation for the current study.
This study paves the way for future exploration of novel topological phenomena.
Phase transition characterized by the jump of spin vector and tensor. (Image by ZHANG Mengxiang et al.)
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