Topological energy transfer in an optomechanical system with exceptional points

• Published in: Nature (London) 2016-09, Vol.537 (7618), p.80-83
• Main Authors: Xu, H., Mason, D., Jiang, Luyao, Harris, J. G. E.
• Format: Article
• Language: English
• Subjects: 639/766/1130/2800; 639/766/400/482; Cryostats; Energy; Energy transfer; Humanities and Social Sciences; Lasers; letter; Mechanical properties; multidisciplinary; Physics research; Radiative transfer; Science; Silicon nitrides; Topology
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature18604

The transfer of energy between two vibrational modes of an optomechanical device is achieved using topological operations; the key to this transfer is the existence of an exceptional point in the complex spectrum of the device. Exceptional points promise exotic prizes In physical systems with gain and loss modes, unusual behaviour can arise at so-called exceptional points where such modes coalesce. In previous work on optical systems, exceptional points have been harnessed to realize effects such as unidirectional light transmission and lasing suppression and revival. It is further predicted that slowly encircling exceptional points in parameter space induces non-reciprocal transitions between two states. This intriguing fundamental effect has now been demonstrated experimentally by two independent teams. Jack Harris and colleagues observe energy transfer between two vibrational modes in an optomechanical resonator, and Stefan Rotter and colleagues measure asymmetric mode switching in a microwave transmission line. These studies pave the way for further experimental and fundamental exploration of physical phenomena around exceptional points. Topological operations can achieve certain goals without requiring accurate control over local operational details; for example, they have been used to control geometric phases and have been proposed as a way of controlling the state of certain systems within their degenerate subspaces 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 . More recently, it was predicted that topological operations can be used to transfer energy between normal modes, provided that the system possesses a specific type of degeneracy known as an exceptional point 9 , 10 , 11 . Here we demonstrate the transfer of energy between two vibrational modes of a cryogenic optomechanical device using topological operations. We show that this transfer arises from the presence of an exceptional point in the spectrum of the device. We also show that this transfer is non-reciprocal 12 , 13 , 14 . These results open up new directions in system control; they also open up the possibility of exploring other dynamical effects related to exceptional points 15 , 16 , including the behaviour of thermal and quantum fluctuations in their vicinity.