# Theory of generalized Josephson effects

## TL;DR

This paper generalizes the Josephson effects beyond superconductors to systems with spontaneous continuous symmetry breaking, linking supercurrent flow to Noether currents and predicting novel phenomena like a force oscillation between crystalline solids.

## Contribution

It introduces a unified theoretical framework for Josephson effects applicable to various symmetry-breaking systems, extending beyond superconductivity.

## Key findings

- Identification of the flow as Noether current for broken symmetry
- Prediction of Josephson-like effects between crystalline solids
- Proposal of measurable force oscillations related to separation distance

## Abstract

The DC Josephson effect is the flow of supercurrent across a weak link between two superconductors with a different value of their order parameter, the phase. We generalize this notion to any kind of spontaneous continuous symmetry breaking. The quantity that flows between the two systems is identified as the Noether current associated with the broken symmetry. The AC Josephson effect is identified as the oscillations due to the energy difference between the two systems caused by an imposed asymmetric chemical potential. As an example of novel physics, a Josephson effect is predicted between two crystalline solids, potentially measurable as a force periodic in the separation distance.