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, magic-angle twisted bi-layered graphene, to Kondo quantum dots, often exist close to 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 in experiments across a wide range of materials, the microscopic origin of them is largely un-explained, and it has become an outstanding open problem in correlated electron systems. In this talk, I first take an overview of the SM phenomena. I further offer a microscopic mechanism to uncover this mystery seen in quasi-two-dimensional heavy- fermion metals [1] and superconductors [2]. This mechanism is based on coexistence and 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 [3][4]. The interplay of these two effects via critical spin and charge fluctuations provides an excellent account for the SM phenomena. The extension of this theory [5] to the newly discovered strange metal “phase” (ground state) in a class of paramagnetic frustrated Kondo lattice materials
[6] is discussed.
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[3] Yung-Yeh Chang, Silke Paschen, Chung-Hou Chung, Phys. Rev. B 97, 035156 (2018).
[4] Y.Y. Chang et al., Phys. Rev. B 99, 094513 (2019).
[5] Jiangfan Wang, Yung-Yeh Chang, and Chung-Hou Chung, arXiv: 2005.03427.
[6] H. Zhao et al., Nat. Phys. 15, 1261 (2019).