T. Xiang et al., LOW-TEMPERATURE SUPERFLUID RESPONSE OF HIGH-T-C SUPERCONDUCTORS, International journal of modern physics b, 12(10), 1998, pp. 1007-1032
We have reviewed our theoretical and experimental results of the low t
emperature superfluid response function rho(s)(mu) of high temperature
superconductors (HTSC). In clean high-T-c materials the in-plane supe
rfluid density rho(s)(ab) varies linearly with temperature. The slope
of this linear T term is found to scale approximately with 1/T-c which
, according to the weak coupling BCS theory for a d-wave superconducto
r, implies that the gap amplitude scales approximately with T-c. A T-5
behavior of the out-of-plane superfluid density rho(s)(c) for clean t
etragonal HTSC was predicted and observed experimentally in the single
layer Hg-compound HgBa2CuO4+delta. In other tetragonal high-T-c compo
unds with relatively high anisotropy, such as Hg2Ba2Ca2Cu3O8-delta, rh
o(s)(c) varies as T-2 due to disorder effects. In optimally doped YBa2
Cu3O7-delta, rho(s)(c) varies linearly with temperature at low tempera
tures, but in underdoped YBa2Cu3O7-delta, rho(s)(c) varies as T-2 at l
ow temperatures; these results are consistent with our theoretical cal
culations.