October 19, 2010 11:00

The energy gap in many novel superconductors is highlyanisotropic, with either nodes (zeroes) or deep minima at the Fermisurface. Locating these nodes, i.e. identifying the directions alongwhich the gap vanishes is a crucial step in identifying the correct underlying pairing interactions. I will show that rotation of theapplied magnetic field relative to the nodes produces oscillations inthe specific heat and electronic thermal conductivity that can be usedto determine the location of the gap nodes or minima from bulkmeasurements. I will review the relevant experimental results, anddescribe the current status of the theoretical underpinnings of thesemeasurements, emphasizing the new physics that resolved apparentcontradictions between different probes. I will pay special attentionto the inversion of the anisotropy as a function of temperature andfield, theoretically predicted and recently found experimentally. Iwill provide a comparison of experiment and theory in the 115 heavyfermion compounds, two-dimensional organic superconductors, andpnictides.