Dimensional Crossovers in the Doped Ladder System Spin Gap, Superconductivity and Interladd.pdf
文本预览下载声明
a
r
X
i
v
:
c
o
n
d
-
m
a
t
/
9
8
0
2
1
8
5
v
1
[
c
o
n
d
-
m
a
t
.s
u
p
r
-
c
o
n
]
1
8
F
e
b
1
9
9
8
typeset using JPSJ.sty ver.0.7f
Dimensional Crossovers in the Doped Ladder System: Spin
Gap, Superconductivity and Interladder Coherent Band
Motion
Jun-ichiro Kishine? and Kenji Yonemitsu
Department of Theoretical Studies, Institute for Molecular Science, Okazaki 444-8585, Japan
(Received December 5, 1997)
Based on the perturbative renormalization group (PRG) approach, we have studied
dimensional crossovers in Hubbard ladders coupled via weak interladder one-particle
hopping, t⊥. We found that the one-particle crossover is strongly suppressed through
growth of the intraladder scattering processes which lead the isolated Hubbard ladder
system toward the spin gap metal (SGM) phase. Consequently when t⊥ sets in, there
exists, for any finite intraladder Hubbard repulsion, U 0, the region where the two-
particle crossover dominates the one-particle crossover and consequently the d-wave
superconducting transition, which is regarded as a bipolaron condensation, occurs. By
solving the scaling equations for the interladder one-particle and two-particle hopping
amplitudes, we give phase diagrams of the system with respect to U , t⊥0 (initial value
of t⊥) and the temperature, T . We compared the above dimensional crossovers with
those in a weakly coupled chain system, clarifying the difference between them.
KEYWORDS: doped ladder, dimensional crossover, perturbative renormalization-group, spin gap metal,
bipolaron condensation, d-wave superconductivity
§1. Introduction
Magnetic and electronic properties of ladder materials have attracted great interest. [1]
Central to these issues are the effects of the unusual spin-liquid state with a spin excitation
gap in the undoped parent system on the electronic conduction in the doped system. Last
year Uehara et al. [2] discovered a superconductivity signal in the doped ladder system,
Sr14?xCaxCu24O41, under pressure. The comp
显示全部