A mechanism for Planckian metal phase in overdoped cuprate superconductors

Yung-Yeh Chang^1,2,3*, Khoe Van Nguyen³, Chung-Hou Chung^2,3

¹Institute of physics, Academia Sinica, Taipei, Taiwan
²Physics Division, National Center for Theoretical Sciences, Taipei, Taiwan
³Department of Electrophysics, National Yang Ming Chiao Tung University, Hsinchu, Taiwan

* Presenter:Yung-Yeh Chang, email:cdshjtr@gmail.com

The mysterious metallic phase showing perfect T-linear resistivity and a universal scattering rate 1/τ=αk_BT/ħ with an universal prefactor α ~1 and logarithmic-in-temperature singular specific heat coefficient, so-called “Planckian metal phase” was observed in various overdoped high-T_c cuprate superconductors over a finite range in doping. The microscopic origin of these exotic behaviors remains elusive. Here, we offer a mechanism for this phenomenon based on quantum critical charge fluctuations within slave-boson approach to the two-dimensional t-J model. This model is further mapped onto an effective Kondo-Heisenberg-like Hamiltonian. Via perturbative renormalization group analysis of this effective model, a quantum critical Planckian metal phase is realized near a localized-delocalized transition where bosonic charge (effective Kondo) fluctuations coupled to conduction band and gapless fermionic spinons. The Planckian phase we realized here bears a striking similarity to the strange metal state found in heavy-fermion Kondo lattice systems where the strange metal behaviors are accompanied by the Fermi surface reconstruction over the same parameter region due to quantum critical Kondo (charge) fluctuations. The relevance of our results for overdoped cuprates is discussed.

The authors acknowledge the support from NSTC, NCTS od Taiwan.

Keywords: Cuprate superconductors, Planckian metal, Heavy-fermion Kondo lattice