Spin-charge gauge approach to the pseudogap phase of high-Tccuprates: Theory versus experiments

Abstract

We consider as a clue to the understanding of the pseudogap phase in high-T-c superconductors the metal-insulator crossover in underdoped, nonsuperconducting cuprates as temperature decreases and a similar crossover in superconducting cuprates when a strong magnetic field suppresses superconductivity. A spin [SU(2)] and charge [U(1)] Chern-Simons gauge field theory, applied to the t-J model, is developed to describe this striking phenomenon. Two length scales have been derived from the theory: the antiferromagnetic correlation length xiapproximate to(deltaparallel toln deltaparallel to)(-1/2), where delta is the doping concentration, and the thermal de Broglie wavelength of the dissipative charge carriers lambda(T)approximate to(Tdelta/t)(-1/2), where T is the temperature, t the hopping integral. At low temperatures xiless than or equal tolambda(T), the antiferromagnetic short-range order dominates, and the charge carriers become localized, showing insulating behavior. On the contrary, at high temperatures xigreater than or similar tolambda(T), the dissipative motion of charge carriers prevails, exhibiting metallic conductivity. Furthermore, the gauge interaction induces binding of spinons (spin excitation) and holons (charge carrier) into electron resonance. This process introduces a new energy scale, the inverse recombination time, which turns out to be essential in the interpretation of the out-of-plane resistivity. The major steps in the theoretical derivation of these results, particularly the calculation of the current-current correlation function and the Green's function for the physical electron, are presented with some detail. The obtained theoretical results are systematically compared with the in-plane and out-of-plane resistivity data and the magnetoresistance data, as well as the nuclear magnetic relaxation data in the pseudogap regime. Very good agreement is obtained.