Andreas Rückriegel, Andreas Kreisel, Peter Kopietz
We generalize the spin-wave expansion in powers of the inverse spin to
time-dependent quantum spin models describing rotating magnets or magnets in
time-dependent external fields. We show that in these cases, the spin operators
should be projected onto properly defined rotating reference frames before the
spin components are bosonized using the Holstein-Primakoff transformation. As a
first application of our approach, we calculate the reorganization of the
magnetic state due to Bose-Einstein condensation of magnons in the magnetic
insulator yttrium-iron garnet; we predict a characteristic dip in the
magnetization which should be measurable in experiments.
View original:
http://arxiv.org/abs/1111.2052
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