Direct Observation of Nodal Quasiparticles in an Unconventional Superconductor: Field-angle Dependent Heat Capacity of YNi2B2C

TL;DR

This study uses field-angle dependent heat capacity measurements to directly observe nodal quasiparticles in the unconventional superconductor YNi2B2C, revealing fourfold oscillations linked to its gap structure.

Contribution

It provides the first direct observation of nodal quasiparticles in YNi2B2C through angular heat capacity measurements, confirming theoretical predictions.

Findings

Fourfold oscillation in heat capacity observed

Nodal quasiparticles generated along <100> directions

Strong agreement between experiment and Doppler effect theory

Abstract

Field-angle dependent heat capacity of the non-magnetic borocarbide superconductor YNi2B2C reveals a clear fourfold oscillation, the first observation of its kind. The observed angular variations were analyzed as a function of magnetic field angle, field intensity and temperature to provide its origin. The quantitative agreement between experiment and theory strongly suggests that we are directly observing nodal quasiparticles generated along <100> by the Doppler effect. The results demonstrate that field-angle heat capacity can be a powerful tool in probing the momentum-space gap structure in unconventional superconductors such as high Tc cuprates, heavy fermion superconductors, etc.