重费米子体系中演生量子态及其调控的研究进展

Research Progress on Emergent Quantum States and Manipulations in Heavy Fermion Systems

作为典型的强关联电子体系,重费米子材料表现出丰富的量子基态,如反铁磁序、铁磁序、非常规超导、非费米液体、自旋液体、轨道序和拓扑态等。相比其他强关联电子体系,重费米子体系的特征能量尺度低,可以通过压力、磁场或掺杂等参量对不同量子态进行连续调控,因而是研究量子相变、超导及其相互作用的理想体系。本文重点介绍国家重点研发计划项目"重费米子体系中的演生量子态及其调控"执行两年来,在重费米子电子相图、量子相变、超导、强关联拓扑态、微观电子态等前沿科学问题上的研究进展。着重介绍了重费米子超导体CeCu_2Si_2的超导序参量,在重费米子材料YbPtBi中发现的外尔费米子激发,低载流子浓度近藤晶体中的关联拓扑电子态,以及CeTIn_5体系中的局域-巡游转变和重费米子态的微观机理研究等。这些研究成果加深了我们对重费米子体系中丰富的演生量子态及其调控的理解,为项目后期研究的凝练和深化奠定了坚实的基础。

As prototypical strongly correlated electron systems,heavy fermion materials exhibit diverse quantum ground states,such as antiferromagnetism,ferromagnetism,unconventional superconductivity,non-Fermi-liquid,quantum spin liquid,orbital order and topological states.In contrast to other strongly correlated systems,heavy fermions have relatively small characteristic energy scales,and therefore are susceptible to continuous tuning by external parameters such as pressure,magnetic field and chemical doping.Heavy fermions thus serve as ideal systems for studying quantum phase transitions,superconductivity and their intricate relationship.In this article,we report our research progress for the National Key R&D Program"The emergent quantum states and their tuning in heavy fermion systems"over the past two years,including our results on electronic phase diagrams,quantum phase transitions,superconductivity,strongly correlated topological states and microscopic electronic states.We highlight our studies of the superconducting order parameter of the heavy fermion superconductor CeCu2Si2,the discovery of Weyl fermion excitations in YbPtBi,other studies of topology in the Kondo lattice systems ReX(Re=rare earth,X=Sb,Bi)with low carrier densities,and the local-itinerant transition together with its microscopic mechanism in the heavy fermion states of the CeTIn5 system.These fruitful results have deepened our understanding of emergent quantum states and their tuning in heavy fermions,and laid a solid foundation for future research in the following years.