Physicists exploit space and time symmetries to control quantum
materials

Date:
December 2, 2021
Source:
University of Exeter
Summary:
Physicists 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.



FULL STORY ========================================================================== 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 behaviour 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
emphasises 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." ========================================================================== Story Source: Materials provided by University_of_Exeter. Note: Content
may be edited for style and length.


========================================================================== Journal Reference:
1. Charles Andrew Downing, Vasil Arkadievich Saroka. Exceptional
points in
oligomer chains. Communications Physics, 2021; 4 (1) DOI:
10.1038/s42005- 021-00757-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/12/211202141535.htm

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