低载流子浓度近藤半金属的合成探索及其量子相变的研究

近藤晶格体系可以实现从长程磁有序到非磁性费米液体的量子相变，其强烈的量子涨落常导致一些新奇量子态的出现。近藤晶格体系不仅仅包括了重费米子金属和近藤绝缘体，还包括研究较少的近藤半金属。在低载流子浓度下，没有足够多的导带电子去屏蔽局域磁矩，近藤相干的能量尺度会远小于单杂质的近藤温度，从而延迟了费米液体基态的形成，这也是经典的Nozières耗散问题。近藤半金属在一定的调控下，RKKY作用、近藤效应以及低载流子浓度三者间的竞争效应，使量子相变复杂而有趣。首先，本项目探索合成新型的低载流子浓度铈基近藤半金属高质量单晶，并对其物理性质展开详细的研究；其次，应用磁场、压力、掺杂等手段对其基态进行调控，建立起低载流子极限下的量子相变相图；最后结合非弹性中子散射技术研究量子临界点附近磁激发的动态磁化率虚部的标度行为，进一步研究该体系下量子相变的演化机理以及Nozières耗散问题对量子临界行为的影响。

The Kondo lattice system can realize the quantum phase transition from long-range magnetic order to non-magnetic Fermi liquid, and its strong quantum fluctuations often lead to the appearance of some novel quantum states. The Kondo lattice includes not only commonly known heavy fermion metal and Kondo insulator, but also Kondo semimetals that are less studied. In the low carrier density limit, there are insufficient conduction band electrons to shield the local magnetic moment, and the energy scale of the coherence Kondo screening will be much lower than that of the single-impurity Kondo screening, thereby delaying the formation of the Fermi liquid ground state, which is also a classic Nozières dissipation problem. Under certain regulation, Kondo semimetals have competitive effects among long-range magnetic order, Kondo effect, and low-carrier-density, which make the quantum phase transition complex and interesting. This project firstly focuses on exploring the synthesis of a new type of low-carrier-density Ce-based Kondo semimetal single crystal with high quality, and conducts detailed research on its physical properties. Secondly, apply magnetic field, pressure, doping and other means to tune its ground state, and establish the quantum phase transition phase diagram under the limit of low-carrier-density. Finally, the inelastic neutron scattering technique is used to study the scaling behavior of the imaginary part of the dynamic susceptibility near the quantum critical point, and further study the evolution mechanism of quantum phase transition in this system and the influence of Nozières dissipation problem on quantum critical behavior.