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In condensed matter physics, nuclear magnetic resonance (NMR) is a powerful local probe to reveal intrinsic static magnetism and low-energy fluctuations. In our research group, we developed NMR techniques to combine with high-pressure, ultra-low temperature, and high-field conditions, in order to search for new quantum states and novel quantum criticality arising from quantum phase transitions. In this talk, I will report our recent NMR studies on several low-dimensional and/or frustrated systems, which reveal novel ground states and quantum phase transitions. In a honeycomb lattice magnet α-RuCl3, we discovered a possible field-induced proximit Kitaev quantum spin liquid with gapless excitations [1] and a pressure-induced valence-bond-solid (VBS) state [2]. Our studies on Ba8CoNb6O24 demonstrate that it benchmarks behaviors for 2D triangular lattice antiferromagnet, also with a spin-liquid-like behavior and field-induced magnetic ordering [3]. We also clarified that pressure induces a stripe-type antiferromagnetism in a high-temperature superconductor FeSe which provide important ingredients for understanding the origin of superconductivity in this compound [4].
References
[1] J. Zheng et al., PRL 119, 227208 (2017);
[2] Y. Cui et al., PRB 96, 215047 (2017).
[3] Y. Cui et al., PRM 2, 044403 (2018)
[4] P.?S. Wang et al., PRL 117, 237001 (2016).
于伟强，中国人民大学物理系教授。2004年获得UCLA博士学位，后在马里兰大学、马克马斯特大学做博士后，2008年起任现职。2011年获国家基金委首届优青资助。结合极低温、高压和高磁场技术，搭建了特色的低温固体核磁共振系统，专注于铁基高温超导材料和量子磁性材料的物性研究，目前共发表60多篇学术论文。近几年以通讯作者在《物理评论快报》发表5篇学术论文。在铁基高温超导材料的超导对称性、向列序、自旋涨落和超导的关联，以及自旋阻挫材料的自旋液体态等方面做出前沿研究成果。