Eur. Phys. J. B 81, 69-77 (2011)
https://doi.org/10.1140/epjb/e2011-20096-y

Optical properties of the pseudogap state in underdoped cuprates

¹ Department of Physics, University of Guelph, N1G 2W1 Guelph, Ontario, Canada
² Department of Physics and Astronomy, McMaster University, L8S 4M1 Hamilton, Ontario, Canada
³ The Canadian Institute for Advanced Research, M5G 1Z8 Toronto, Ontario, Canada

Corresponding author: ^a adamrpound@gmail.com

Received: 7 February 2011
Revised: 4 March 2011
Published online: 8 April 2011

Abstract

Recent optical measurements of deeply underdoped cuprates have revealed that a coherent Drude response persists well below the end of the superconducting dome. In addition, no large increase in optical effective mass has been observed, even at dopings as low as 1%. We show that this behavior is consistent with the resonating valence bond spin-liquid model proposed by Yang, Rice, and Zhang. In this model, the overall reduction in optical conductivity in the approach to the Mott insulating state is caused not by an increase in effective mass, but by a Gutzwiller factor, which describes decreased coherence due to correlations, and by a shrinking of the Fermi surface, which decreases the number of available charge carriers. We also show that in this model, the pseudogap does not modify the low-temperature, low-frequency behavior, though the magnitude of the conductivity is greatly reduced by the Gutzwiller factor. Similarly, the profile of the temperature dependence of the microwave conductivity is largely unchanged in shape, but the Gutzwiller factor is essential in understanding the observed difference in magnitude between ortho-I and -II YBa₂Cu₃O_y.