Non-reciprocal energy transfer through the Casimir effect

• Published in: Nature nanotechnology Vol. 17; no. 2; pp. 148 - 152
• Main Authors: Xu, Zhujing, Gao, Xingyu, Bang, Jaehoon, Jacob, Zubin, Li, Tongcang
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01-02-2022; Nature Publishing Group
• Subjects: 132/124; 639/624/400/482; 639/766/400/482; 639/766/483; 639/925/927/1021; Chemistry and Materials Science; Energy; Energy transfer; Fluctuations; Letter; Materials Science; Nanotechnology; Nanotechnology and Microengineering; Oscillators; Parameters; Quantum mechanics; Quantum theory; Resonant frequencies; Vacuum; Zero point energy
• ISSN: 1748-3387; 1748-3395
• DOI: 10.1038/s41565-021-01026-8

One of the fundamental predictions of quantum mechanics is the occurrence of random fluctuations in a vacuum caused by the zero-point energy. Remarkably, quantum electromagnetic fluctuations can induce a measurable force between neutral objects, known as the Casimir effect
1
, and it has been studied both theoretically
2
,
3
and experimentally
4
–
9
. The Casimir effect can dominate the interaction between microstructures at small separations and is essential for micro- and nanotechnologies
10
,
11
. It has been utilized to realize nonlinear oscillation
12
, quantum trapping
13
, phonon transfer
14
,
15
and dissipation dilution
16
. However, a non-reciprocal device based on quantum vacuum fluctuations remains an unexplored frontier. Here we report quantum-vacuum-mediated non-reciprocal energy transfer between two micromechanical oscillators. We parametrically modulate the Casimir interaction to realize a strong coupling between the two oscillators with different resonant frequencies. We engineer the system’s spectrum such that it possesses an exceptional point
17
–
20
in the parameter space and explore the asymmetric topological structure in its vicinity. By dynamically changing the parameters near the exceptional point and utilizing the non-adiabaticity of the process, we achieve non-reciprocal energy transfer between the two oscillators with high contrast. Our work demonstrates a scheme that employs quantum vacuum fluctuations to regulate energy transfer at the nanoscale and may enable functional Casimir devices in the future.
Quantum fluctuation in a vacuum can induce a measurable force between neutral objects in close vicinity. By dynamically modulating a system of two micromechanical oscillators near an exceptional point in the parameter space, this so-called Casimir effect can induce a non-reciprocal, diode-like energy transfer.