3d X-Y scaling of the specific heat of YBa 2Cu 3O 7−δ single crystals

Abstract

The specific heat of a single crystal sample of YBa 2Cu 3O 7−δ (YBCO) has been measured with magnetic fields up to 8 Tesla applied parallel to the c-axis of the crystal. We analyse the data in terms of the Lowest Landau Level (LLL) and critical scaling theories. Recent measurements of magnetisation and resistivity have been unable to distinguish between the critical scaling and LLL regimes. We find that the data does not scale using the LLL theory and therefore conclude that the LLL theory is not applicable in magnetic fields less than 8 Tesla. However, we find that the data does scale using the 3-dimensional XY model. This provides strong evidence for the existence of a critical regime within which there is scaling behaviour characteristic of the 3-dimensional XY model with critical exponents consistent with those observed in superfluid 4He.