Specific heat of YBa2Cu3O7  δ single crystals: Implications for the vortex structure
Abstract
The anisotropy of the magnetic field dependence of the specific heat of YBa$_2$Cu$_3$O$_{7  {\rm \delta}}$ can be used to identify different lowenergy excitations, which include phonons, spin$ \frac{1}{2}$ particles, and electronic contributions. With a magnetic field H applied perpendicular to the copper oxide planes, we find that the specific heat includes a linearT term proportional to $\sqrt{H}$. The nonlinear field dependence of the density of states at the Fermi level suggests that there are quasiparticle excitations throughout the entire vortex, not just in the vortex core. The $\sqrt{H} T$ term agrees quantitatively with G. Volovik's prediction for a superconductor with lines of nodes in the gap. A similar, but much smaller, effect is predicted for fields parallel to the planes, and sensitive measurements of the inplane anisotropic magnetic field dependence of the specific heat could be used to map out the nodes.
 Publication:

Journal of Physics and Chemistry of Solids
 Pub Date:
 December 1995
 DOI:
 10.1016/00223697(95)001638
 arXiv:
 arXiv:condmat/9505129
 Bibcode:
 1995JPCS...56.1899M
 Keywords:

 Condensed Matter
 EPrint:
 14 pages (LaTeX2e) plus 6 uuencoded .eps figures