https://doi.org/10.1007/s100510070178
Some consequences of electronic topological transition in 2D system on a square lattice: Excitonic ordered states
1
Laboratoire Léon Brillouin, CE-Saclay, 91191
Gif-sur-Yvette, France
2
Russian Research Center "Kurchatov
Institute", 123 182 Moscow, Russia
Received:
9
June
1999
Published online: 15 August 2000
We study in a mean-field approximation
the ordered "excitonic"states which develop
around the quantum critical point (QCP) associated with the
electronic topological transition (ETT) in a 2D electron system on
a square lattice. We consider the case of hopping beyond nearest
neighbors when ETT has an unusual character. We show that the
amplitude of the order parameter (OP) and of the gap in the
electron spectrum increase with increasing the distance from the
QCP, 
, where 
and n is an
electron concentration. Such a behavior is different from the
ordinary case when OP and the gap decrease when going away from
the point which is a motor for instability. We show that the
chemical potential lies always inside the gap for wavevectors
in a proximity of 
whatever is the doping
concentration. The spectrum gets a characteristic flat shape as a
result of hybridization effect in the vicinity of two different
SP's. The shape of the spectrum as a function of 
and the angle dependence of the
gap have a striking similarity with the features observed in the
normal state of the underdoped high-Tc cuprates. We discuss
also details about the phase diagram and the behaviour of the
density of states.
PACS: 74.25.-q – General properties; correlations between physical properties in normal and superconducting states / 74.72.-h – High-Tc compounds / 74.25.Dw – Superconductivity phase diagrams / 74.25.Ha – Magnetic properties
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2000
