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.

 

References:
[1] H. Zhao, J. Zhang, M. Lyu, S. Bachus, Y. Tokiwa, P. Gegenwart, S. Zhang, J. Cheng, Y.-f. Yang, G. Chen, Y. Isikawa, Q. Si, F. Steglich, and P. Sun, Nat. Phys. 15, 1261 (2019).
[2] Yung-Yeh Chang, Silke Paschen, Chung-Hou Chung, Phys. Rev. B 97, 035156 (2018).
[3] Y.Y. Chang et al., Phys. Rev. B 99, 094513 (2019).
[4] Jiangfan Wang, Yung-Yeh Chang, and Chung-Hou Chung, arXiv: 2005.03427.