Test of the Equivalence Principle for Superconductors

TL;DR

This study tests the weak equivalence principle using a cryogenic torsion balance with superconducting and normal materials, setting new limits on possible violations and contributing to fundamental physics tests.

Contribution

It provides the first experimental constraints on equivalence principle violations involving superconductors and Cooper pairs.

Findings

Eötvös parameter for superconducting niobium constrained to ≤ 2.0×10⁻⁹

Eötvös parameter for Cooper pairs constrained to ≤ 9.2×10⁻⁴

No violation of the equivalence principle detected within experimental limits

Abstract

We searched for violations of the weak equivalence principle using a cryogenic torsion balance with a pendulum comprised of superconducting niobium and copper. We constrain the E\"otv\"os parameter with 95%-confidence to $\eta_{\text{Nb*-Cu}}~\leq~2.0\times10^{-9}$ and $\eta_{\text{CP-ee}}\leq9.2\times10^{-4}$ for superconducting niobium and Cooper pairs, respectively.