近日，中国科学技术大学的曾长淦&张汇及其研究团队取得一项新进展。经过不懈努力，他们实现卡西米尔力的磁场调谐。相关研究出成果已于2024年5月24日在国际知名学术期刊《自然—物理学》上发表。

据悉，量子涨落引起的卡西米尔力可以是吸引的，也可以是排斥的，这取决于所涉及的材料的介电常数和磁导率。然而，利用外场控制大多数材料的介电常数是具有挑战性的。相比之下，铁磁流体的磁导率可以很容易地通过磁场调谐，这为卡西米尔力的磁场调谐提供了可能。

该研究团队证明这种调谐可以使一个金球和硅板能够浸泡在水基铁磁流体。理论计算预测，通过改变磁场、分离距离和铁磁流体体积分数，卡西米尔力可以在很宽的参数范围内从吸引调节到排斥。实验上，研究人员开发了一个悬臂设计进行测量水基铁磁流体。通过使用这种设置，他们观察到预测的转换。这些发现可能会促进基于卡西米尔效应的可开关微机械器件的发展。

附：英文原文

Title: Magnetic-field tuning of the Casimir force

Author: Zhang, Yichi, Zhang, Hui, Wang, Xiuxia, Wang, Yiheng, Liu, Yuchen, Li, Shu, Zhang, Tianyi, Fan, Chuang, Zeng, Changgan

Issue&Volume: 2024-05-24

Abstract: The quantum fluctuation-induced Casimir force can be either attractive or repulsive, depending on the dielectric permittivities and magnetic permeabilities of the materials involved. However, it is challenging to manipulate the dielectric permittivities of most materials using external fields. In contrast, the magnetic permeabilities of ferrofluids can be readily tuned by magnetic fields, which opens up the possibility of magnetic-field tuning of the Casimir force. Here, we demonstrate that this tuning can be achieved for a gold sphere and a silica plate immersed in water-based ferrofluids. Our theoretical calculations predict that, by varying the magnetic field, separation distance and ferrofluid volume fraction, the Casimir force can be tuned from attractive to repulsive over a wide range of parameters in this system. Experimentally, we develop a cantilever designed to conduct measurements within water-based ferrofluids. Using this setup, we observe the predicted transitions. These findings may lead to the development of switchable micromechanical devices based on the Casimir effect.

DOI: 10.1038/s41567-024-02521-0

Source: https://www.nature.com/articles/s41567-024-02521-0