  Anderson-Higgs mechanism of mass generation is a generic concept in
high-energy and condensed matter physics. It shows up through the Meissner
effect providing the expulsion of static and low-frequency magnetic fields from
superconductors. However, it does not affect propagating electromagnetic waves
with a spectrum gap determined by the plasma frequency, which is too large to
be sensitive to the superconducting transition. Here we demonstrate the
spectroscopic manifestation of the Anderson-Higgs mass, showing that it
determines the spectrum gap of magnons in
superconductor/ferromagnet/superconductor multilayers. Moreover, we show that
this effect has been observed in recent experiments as a spontaneous
ferromagnetic resonance frequency shift in such systems. Our theory explains
many unusual experimental features and suggests effective controls over the
magnon spectrum with tunable spectral gap and group-velocity reversal. These
findings pave the way to a wide range of advanced functionalities for possible
applications in magnonics.
