Higher-order and fractional discrete time crystals in clean long-range interacting systems
A team of current and former TCM researchers showed how long-range interactions can be leveraged to realise higher-order and fractional discrete time crystals.
Extending the notion of phases of matter to the non-equilibrium realm, discrete time crystals (DTCs) have recently attracted a lot of attention. In essence, DTCs are periodically driven systems that, rather than inheriting the frequency of the drive, respond with a smaller one. Generally, the ratio between the two frequencies, of the drive and of the system's response, is set by the size of the local Hilbert space of the system's building blocks. As a prototypical example, many-body localised (MBL) chains of spins 1/2 in the presence of disorder can (only) realize period-doubled 2-DTCs. The authors show that this limitation can be lifted in long-range interacting systems without disorder. In fact, the system can in this case respond with periods in excess of the one of the drive by integer as well as fractional factors larger than 2: the realisation of higher-order and fractional DTCs. By means of a combination of techniques, the authors demonstrate for an experimentally-friendly model that a zoo of exotic time-crystalline behaviors appears in these systems, opening the way towards the study of novel dynamical behaviours beyond the MBL paradigm.
Pizzi, A., Knolle, J., and Nunnenkamp, A., "Higher-order and fractional discrete time crystals in clean long-range interacting systems." Nature Communications 12.1 (2021): 1-7.