Resistive transition and upper critical field in underdoped YBa2Cu3O6+x
single crystals |
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Authors: | V F Gantmakher G E Tsydynzhapov L P Kozeeva A N Lavrov |
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Institution: | (1) Institute of Solid State Physics, Russian Academy of Sciences, 142432 Chernogolovka, Moscow Region, Russia;(2) Institute of Inorganic Chemistry, Siberian Department of, Russian Academy of Sciences, 630090 Novosibirsk, Russia |
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Abstract: | A superconducting transition in the temperature dependence of the ab-plane resistivity of underdoped YBa2Cu3O6+x
crystals in the range T
c≲30 K has been investigated. Unlike the case of samples with the optimal level of doping, the transition width increased insignificantly
with magnetic field, and in the range T≲13 K it decreased with increasing magnetic field. The transition point T
c(B) was determined by analyzing the fluctuation conductivity. The curves of B
c2(T) measured in the region T/T
c≳0.1 did not show a tendency to saturation and had a positive second derivative everywhere, including the immediate neighborhood
of T
c. The only difference among the curves of B
c2(T) for different crystal states is the scales of Tand B, so they can be described in terms of a universal function, which fairly closely follows Alexandrov’s model of boson superconductivity.
Zh. éksp. Teor. Fiz. 115, 268–284 (January 1999) |
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Keywords: | |
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