Clapping Modes in Unconventional Superconductors

• Clapping modes are collective excitations defined by the relative oscillations between paired components of an ordered state in chiral superconductors.
• They exhibit bosonic sub-gap behavior with clear spectroscopic and transport signatures that aid in identifying time-reversal-symmetry-breaking superconductivity.
• In fluid mechanics and nanomechanics, 'clapping modes' refer to sequential kinematics, illustrating a distinct concept from superconducting order-parameter oscillations.

Searching arXiv for papers on clapping modes across superconductivity and fluid mechanics. Clapping modes are collective excitations associated with internal relative oscillations between components of an ordered state. In contemporary arXiv literature, the term is used most precisely in unconventional superconductivity, where it denotes the relative amplitude and relative phase modes between two chiral components of Cooper pairs, such as the $k_x+i k_y$ and $k_x-i k_y$ sectors of a chiral $p$-wave state. These excitations are bosonic, generically sub-gap, and often long-lived; their spectroscopic and transport signatures have become a central route to identifying chiral and more general time-reversal-symmetry-breaking superconductivity (Matsushita et al., 2021). The same word also appears in fluid mechanics, flight biomechanics, and nanomechanics, but there it refers to closing-body or sequential-mode kinematics rather than to an order-parameter collective mode.

1. Order-parameter meaning in chiral and TRSB superconductors