J. Kishine et K. Yonemitsu, SPIN GAP AND SUPERCONDUCTIVITY IN WEAKLY COUPLED LADDERS - INTERLADDER ONE-PARTICLE VS. 2-PARTICLE CROSSOVER, Journal of the Physical Society of Japan, 66(12), 1997, pp. 3725-3728
Effects of the interladder one-particle hopping, t(perpendicular to),
on the low-energy asymptotics of a weakly coupled Hubbard ladder syste
m have been studied, based on the perturbative renormalization-group a
pproach. We found that for finite intraladder Hubbard repulsion, U, th
ere exists a crossover value of the interladder one-particle hopping,
t(perpendicular to c). For 0 < t(perpendicular to) < t(perpendicular t
o c), the spin gap metal (SGM) phase of the isolated ladder transits a
t a finite transition temperature, T-c, to the d-wave superconducting
(SCd) phase via a two-particle crossover. In the temperature region, T
< T-c, interladder coherent Josephson tunneling of the Cooper pairs o
ccurs, while the interladder coherent one-particle process is strongly
suppressed. For tie < tl, around a crossover temperature, T-cross, th
e system crosses over to the two-dimensional (2D) phase via a one-part
icle crossover. In the temperature region, T < T-cross, the interladde
r coherent band motion occurs.