Ground state of the superconducting compound YBa2Cu3Ox at x<6.5
Aleksandrov I. V., Volodin A. P. , Makarenko I. N. , Svistov L. E. , Stishov S. M.
A study has been made of how the superconducting properties of YBa2Cu3Ox single crystals are affected by a low-temperature annealing under conditions which rule out a loss of oxygen. A sufficiently long annealing completely erases the superconductivity of YBa2Cu3Ox at χ < 6.5. Tunneling measurements carried out for a superconducting single crystal with χ ~ 6.32 showed that the gap feature on the current-voltage characteristic is observed over only ~ 60% of the area of the sample. It is confirmed that the ground state of YBa2Cu30;c at χ < 6.5 is an insulating state.