AC Josephson effect between two superfluid time crystals

Autti, S. and Heikkinen, P.J. and Mäkinen, J.T. and Volovik, G.E. and Zavjalov, V.V. and Eltsov, V.B. (2021) AC Josephson effect between two superfluid time crystals. Nature Materials, 20. 171–174. ISSN 1476-1122

Text (TimeCrystalJosephson)
TimeCrystalJosephson.pdf - Accepted Version
Available under License Unspecified.
Download (503kB)

Abstract

Quantum time crystals are systems characterized by spontaneously emerging periodic order in the time domain1. While originally a phase of broken time translation symmetry was a mere speculation, a wide range of time crystals has been reported. However, the dynamics and interactions between such systems have not been investigated experimentally. Here we study two adjacent quantum time crystals realized by two magnon condensates in superfluid 3He-B. We observe an exchange of magnons between the time crystals leading to opposite-phase oscillations in their populations—a signature of the AC Josephson effect6—while the defining periodic motion remains phase coherent throughout the experiment. Our results demonstrate that time crystals obey the general dynamics of quantum mechanics and offer a basis to further investigate the fundamental properties of these phases, opening pathways for possible applications in developing fields, such as quantum information processing. © 2020, The Author(s), under exclusive licence to Springer Nature Limited.