Superfluid density in the underdoped YBa2Cu3O7-x: evidence for d-density-wave order of the pseudogap.
The investigation of the penetration depth lambda(ab)(T,p) in YBa2Cu3O7-x crystals allowed one to observe the following features of the superfluid density n(s)(T,p) proportional, variant lambda(-2)(ab)(T,p) as a function of temperature T<T(c)/2 and carrier concentration 0.078< or p < or = 0.16 in CuO2 planes: (i) n(s)(0,p) depends linearly on p; (ii) the derivative absolute value of dn(s)(T,p)/dT (T-->0) depends on p slightly in the optimally and moderately doped regions (0.10<p< or =0.16), however, it rapidly increases with p further lowering; (iii) the latter finding is accompanied by the linear low-temperature dependence [-Delta n(s)(T)] proportional, variant T changing to [-Delta n(s)(T)] proportional, square root of T. All these peculiarities can be treated in the framework of the d-density-wave scenario of electronic processes in underdoped high-T(c) materials.
Institute of Solid State Physics RAS, 142432 Chernogolovka, Moscow District, Russia.
M R
MR
Trunin
Yu A
YA
Nefyodov
A F
AF
Shevchun