Circumventing Magnetic Reciprocity: a Diode for Magnetic Fields

TL;DR

This paper demonstrates that a moving conductive material can break magnetic reciprocity, creating a diode-like effect for magnetic fields, which challenges a fundamental symmetry in classical electromagnetism.

Contribution

It introduces a method to achieve unidirectional magnetic coupling using a moving conductor, breaking the traditional symmetry of mutual inductance.

Findings

Experimental verification of asymmetric magnetic coupling

Moving conductors can break magnetic reciprocity

Potential for novel magnetic device applications

Abstract

Lorentz reciprocity establishes a stringent relation between electromagnetic fields and their sources. For static magnetic fields, a relation between magnetic sources and fields can be drawn in analogy to the Green's reciprocity principle for electrostatics. Here we theoretically and experimentally show that a linear and isotropic electrically conductive material moving with constant velocity is able to circumvent the magnetic reciprocity principle and realize a diode for magnetic fields. This result is demonstrated by measuring an extremely asymmetric magnetic coupling between two coils that are located near a moving conductor. The possibility to generate controlled unidirectional magnetic couplings breaks down one of the most deeply-established relations in classical electromagnetism, namely that mutual inductances are symmetric. This result might provide novel possibilities for applications and technologies based on magnetically coupled elements.