We report the results of a study of the effect of structural relaxation on the basal-plane conductivity of heavily underdoped high- Tc YBa 2 Cu 3 O 7−δ single crystals. An increase of the oxygen deficiency in YBa 2 Cu 3 O 7−δ has been found to strengthen localization effects and to lead to the realization of a transition of the metal–insulator type, which always precedes the superconducting transition. In addition, a 5-day room-temperature annealing of the samples has been revealed to result in a notable shift of the metal–insulator transition point toward higher temperatures.
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The final publication is available at Springer via http://dx.doi.org/10.1007/s10909-015-1304-z.
- Metal–insulator transition
- Superconducting cuprates