Physicists from Exeter and Trondheim have developed a theory describing how
space reflection and time reversal symmetries can be exploited, allowing for
greater control of transport and correlations within quantum materials.
Two theoretical physicists, from the University of Exeter (United Kingdom)
and the Norwegian University of Science and Technology (in Trondheim,
Norway), have built a quantum theory describing a chain of quantum
resonators satisfying space reflection and time reversal symmetries. They
have shown how the different quantum phases of such chains are associated
with remarkable phenomena, which may be useful in the design of future
quantum devices relying on strong correlations.
A common distinction in physics is between open and closed systems. Closed
systems are isolated from any external environment, such that energy is
conserved because there is nowhere for it to escape to. Open systems are
connected to the outer world, and via exchanges with the environment they
are subject to energy gains and energy losses. There is an important third
case. When the energy flowing in and flowing out of the system is finely
balanced, an intermediate situation between being open and closed arises.
This equilibrium can occur when the system obeys a combined symmetry of
space and time, that is when (1) switching left and right and (2) flipping
the arrow of time leave the system essentially unchanged.
In their latest research, Downing and Saroka discuss the phases of a quantum
chain of resonators satisfying space reflection and time reversal
symmetries. There are principally two phases of interest, a trivial phase
(accompanied by intuitive physics) and a nontrivial phase (marked with
surprising physics). The border between these two phases is marked by an
exceptional point. The researchers have found the locations of these
exceptional points for a chain with an arbitrary number of resonators,
providing insight into the scaling up of quantum systems obeying these
symmetries. Importantly, the nontrivial phase allows for unconventional
transport effects and strong quantum correlations, which may be used to
control the behavior and propagation of light at nanoscopic length scales.
This theoretical study may be useful for the generation, manipulation and
control of light in low-dimensional quantum materials, with a view to
building light-based devices exploiting photons, the particles of light, as
workhorses down at sizes around one billionth of a meter.
Charles Downing, from the University of Exeter, commented: "Our work on
parity-time symmetry in open quantum systems further emphasizes how symmetry
underpins our understanding of the physical world, and how we may benefit
from it".
Vasil Saroka, from the Norwegian University of Science and Technology,
added: "We hope that our theoretical work on parity-time symmetry can
inspire further experimental research in this exciting area of physics".
"Exceptional points in oligomer chains" is published in Communications
Physics.
Reference:
Charles Andrew Downing et al, Exceptional points in oligomer chains,
Communications Physics (2021).
DOI: 10.1038/s42005-021-00757-3
Tags:
Physics