Enhanced nematic fluctuations near an antiferromagnetic Mott insulator and possible application to high-Tc cuprates

Abstract

Motivated by the widespread experimental observations of nematicity in strongly underdoped cuprate superconductors, we investigate the possibility of enhanced nematic fluctuations in the vicinity of a Mott insulator that displays Néel-type antiferromagnetic order. By performing a strong-coupling expansion of an effective model that contains both Cu-d and O-p orbitals on the square lattice, we demonstrate that quadrupolar fluctuations in the p-orbitals inevitably generate a biquadratic coupling between the spins of the d-orbitals. The key point revealed by our classical Monte-Carlo simulations and large-N calculations is that the biquadratic term favors local stripe-like magnetic fluctuations, which result in an enhanced nematic susceptibility that onsets at a temperature scale determined by the effective Heisenberg exchange J. We discuss the impact of this type of nematic order on the magnetic spectrum and outline possible implications on our understanding of nematicity in the cuprates.

Cuprate superconductors|enhanced nematic fluctuations near the Mott phase

New theoretical results shed some light on the origin of the nematic phase observed in underdoped cuprate superconductors, for which a microscopic theory has so far not being developed. The authors focused on the spin correlations near the Mott insulating phase of the parent compound. They started from a model that captures the Cu and O low-energy degrees of freedom and applied to it a strong-coupling expansion, revealing that the magnetic correlations in the Mott state enhance the nematic susceptibility. These results help to explain the asymmetry observed between hole-doped and electron-doped cuprates (in which nematicity is not observed), as the effect originates from charge fluctuations on the O orbitals and is thus present only in the hole-doped part of the phase diagram.