Pseudogap state of underdoped cuprate HTSC as a display of the Jahn-Teller pseudoeffect

Abstract

For underdoped cuprate HTSC within the framework of the two component model of charge carries (holes and Zhang-Rice polarons) it is considered two near degenerate states of hole molecular orbitals in copper-oxygen plane. These are the state of hole molecular orbitals around one-site Zhang-Rice polarons, and another state is two-site hole molecular orbitals around the two-site oxygen cluster of two nearest Jahn-Teller copper ions with antiferromagnetic ordering spins and with common oxygen ion. Taking into account that the vibronic mixing of these near-degenerate electronic states leads to the Jahn-Teller dynamic effect, in this paper the supposition that the pseudogap state is a consequence of the Jahn-Teller pseudoeffect is discussed. It is shown that existence of two-site Jahn-Teller polaron is consistent with a recent observation of broken time-reversal symmetry in the pseudogap state.