Researchers adjust the Casimir force using magnetic fields

Research teams led by Prof. Zeng Changgan and Zhang Hui of the Hefei National Laboratory for Microscale Physical Sciences, University of Science and Technology of China (USTC) of the Chinese Academy of Sciences have achieved a reversible transition from Casimir attraction to repulsion under magnetic field control using a magnetic fluid as an intermediate medium. Their study was published in Nature Physics.

The Casimir effect is a phenomenon predicted in 1948 by the Dutch physicist Hendrik Casimir. According to this theory, two electrically neutral metal plates in a vacuum experience a submicron-scale attraction due to quantum fluctuations. The Casimir force, in accordance with Lifshitz’s theory, is affected by the dielectric function and magnetic conductivity of materials.

Previous research mainly focused on designing the dielectric function of the material. However, most materials have a dielectric function that is insensitive to external fields, making it difficult to tune the Casimir force using external fields.

In this study, the researchers found that the magnetic conductivity of the magnetofluid can be significantly tuned by a magnetic field. Through ingenious design, they chose to use magnetofluid as an intermediary medium to study the Casimir effect between a gold sphere and a silicon dioxide substrate.

By combining calculations with experiments, the researchers found that the Casimir force can be tuned in a large space of parameters (magnitude of the magnetic field, distance between the gold spheres and the substrate, volume fraction of the magnetic fluid). In particular, they realized a reversible transition from magnetic field-tunable Casimir attraction to repulsion.

Additionally, the researchers developed a special cantilever beam device for measuring the Casimir force in non-transparent liquids.

This study provides new ideas for the future development of microelectromechanical system devices based on the tunable Casimir effect.