Collective mode spectroscopy of unconventional superconductors

The study of unconventional superconducting states remains at the forefront of condensed matter physics research, driven in large part by the desire to understand the superconducting ground states of novel quantum materials. One of the defining features of any superconducting state is its collective mode spectrum, which encodes the dynamics of the order parameter. We will discuss how one can leverage the collective mode spectrum of unconventional superconducting states to gain new insights into their order parameter symmetry, making use of existing experimental probes. In particular, we will discuss the existence and possible detection of two exotic classes of collective modes (orbital “clapping modes” and Cooper pair spin waves) which can be used to identify and characterize time-reversal symmetry breaking superconductors and spin triplet superconductors, respectively.