Unified intermediate coupling description of pseudogap and strange metal phases of cuprates
Hsien-Chung Kao, Dingping Li, B. Rosenstein
Abstract
A one band Hubbard model with intermediate coupling is shown to describe the two most important unusual features of a normal state: linear resistivity strange metal and the pseudogap. Both the spectroscopic and transport properties of the cuprates are considered on the same footing by employing a relatively simple post-Gaussian approximation valid for the intermediate couplings $U/t=1.5--4$ in relevant temperatures $T>100\phantom{\rule{3.33333pt}{0ex}}\mathrm{K}.$ In the doping range $\phantom{\rule{4pt}{0ex}}p=0.1--0.3$, the value of $U$ is smaller than that in the parent material. For a smaller doping, especially in the Mott insulator phase, the coupling is large compared to the effective tight binding scale and a different method is required. This scenario provides an alternative to the paradigm that the coupling should be strong, say $U/t>6$, in order to describe the strange metal. We argue that, to obtain phenomenologically acceptable underdoped normal state characteristics like ${T}^{*}$, pseudogap values, and spectral weight distribution, a large value of $U$ is detrimental. Surprisingly the resistivity in the above temperature range is linear, $\ensuremath{\rho}={\ensuremath{\rho}}_{0}+\ensuremath{\alpha}\frac{{m}^{*}}{{e}^{2}n\ensuremath{\hbar}}T$, with the ``Planckian'' coefficient $\ensuremath{\alpha}$ of order 1.