A rotating screw pump lifts water along its axis, although the position of the screw itself is fixed inside its housing. Similarly, an adiabatic modulation of a periodic potential can move particles from one potential minimum to the next. However, this so-called Thouless pumping loses its quantization in the presence of losses or when the drive is not adiabatic. Zlata Fedorova and colleagues have now shown that the quantization can be recovered if the dissipation is also periodically modulated.
When they incorporated this modulation in their theoretical modelling, counter-propagating modes in a lossy system could no longer hybridize, which restored the quantization — even if the modulation of the driving potential was non-adiabatic. Fedorova and colleagues realized their model using coupled sinusoidal plasmonic waveguides, for which the periodically varying losses were achieved by modulating the cross-section that controls the mode confinement. Despite the optical demonstration, this dissipative Floquet engineering can be applied to a wider class of periodically driven systems.