Normal State Pseudogap and (π,0) Feature in the Underdoped High-TcCuprates: A Microscopic Theory

We show that the pseudogap phenomenon observed in the underdoped cuprates, including such details as the increase of pseudogap with decreasing doping $\delta$, its $T$ independence, its closing at temperature $T_{\mathrm{gap}}^{*}$ which grows with decreasing $\delta$, the gradual destruction of the Fermi surface with decreasing $T$ starting from $T_{\mathrm{gap}}^{*}$, the anomalous form of electron spectral functions as functions of energy, and the form of wave-vector dependence of the “spectrum” around $(0,\pi )$, can be naturally understood within a concept of proximity of the underdoped regime to a 2D electronic topological transition.