A dipole amplifier for electric dipole moments, axion-like particles and a dense dark matter hairs detector

Abstract

A tool that can constrain, in minutes, beyond-the-standard-model parameters like electric dipole moments (EDM) down to a lower-bound $d_\text{e}^{\cal{N}}<10^{-37}\text{e}\cdot\text{cm}$ in bulk materials, or the coupling of axion-like particles (ALP) to photons down to $|G_{a\gamma\gamma}|<10^{-16}$~GeV$^{-1}$, is described. Best limits are $d^n_e<3\cdot10^{-26}\text{e}\cdot\text{cm}$ for neutron EDM and $|G_{a\gamma\gamma}|<6.6\cdot10^{-11}$~GeV$^{-1}$. The {\it dipole amplifier} is built from a superconducting loop immersed in a toroidal magnetic field, $\vec{B}$. When nuclear magnetic moments in the London penetration depth align with $\vec{B}$, the bulk magnetization is always accompanied by an EDM-induced bulk electric field $\vec{E}\propto\vec{B}$ that generates detectable oscillatory supercurrents with a characteristic frequency $\omega_{\text{D}}\propto d_\text{e}^{\cal{N}}$. Cold dark matter (CDM) ALP are formally similar where $\omega_\text{D}\propto |G_{a\gamma\gamma}|\sqrt{n_a/(2m_a)}$ with $m_a$ the ALP mass and $n_a$ its number density. A space probe traversing a dark matter hair with a dipole amplifier is sensitive enough to detect ALP density variations if $|G_{a\gamma\gamma}|\sqrt{n_h/(2m_a)}>4.9\cdot10^{-27}$ where $n_h$ is the ALP number density in the hair.