Unified intermediate coupling description of pseudogap and strange metal phases of cuprates

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 K. In the doping range 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, p = P0 + alpha m* e2nh over line T, with the "Planckian" coefficient alpha of order 1.