中心凝態物理演講:Quantum critical strange metal phase in paramagnetic heavy-fermion Kondo lattice, 1:30 PM, 11/17, 2020
Speaker: Prof. Chung-Hou Chung, National Chiao-Tung University
Time: 1:30PM, 11/17, 2020
Place: 019 Lecture room, Physics Department, NTHU.
Title: Quantum critical strange metal phase in paramagnetic heavy-fermion Kondo lattice
Abstract：
Over the recent decades, there has been growing experimental evidences in correlated electron systems of which thermodynamic and transport properties violate the Landau's Fermi liquid paradigm for metals. These non-Fermi liquid behaviors, ranging from unconventional superconductors, heavy-fermion metals and superconductors to magic-angle twisted bi-layered graphene, often exist near a magnetic quantum phase transition and exhibit so-called "strange metal (SM)" phenomena: with (quasi-)linear-in-temperature resistivity and singular logarithmic-in-temperature specific heat coefficient. In spite of the ubiquitous presence of SM features, the microscopic origin of them is largely un-explained, and it has become an outstanding open problem in correlated electron systems. Recently, an even more exotic quantum critical SM phase was observed in paramagnetic frustrated heavy-fermion materials near Kondo breakdown (KB) [1].
In this talk, I first take an overview of the SM phenomena. I further offer a microscopic mechanism to uncover the mystery of SM seen in Ref. [1]. This mechanism is based on competition between the Kondo correlation and the quasi-2d short-ranged antiferromagnetic resonating-valence-bond spin-liquid near the antiferromagnetic Kondo breakdown quantum critical point [2][3].We establish a controlled theoretical framework to this issue via a dynamical large-N fermionic multichannel approach to the two-dimensional Kondo-Heisenberg lattice model, where KB transition separates a heavy-Fermi liquid from fermionic spin-liquid state [4]. With Kondo fluctuations being fully considered, we find a distinct SM behavior with quasi-linear-in-temperature scattering rate associated with KB. When particle-hole symmetry is present, signatures of a critical spin-liquid SM phase as T à0 are revealed with w/T scaling extended to a wide range. We attribute these features to the interplay of critical bosonic charge (Kondo) fluctuations and gapless fermionic spinons. The implications of our results for the experiments are discussed.