Wideband search for axionlike dark matter using octupolar nuclei in a crystal

Abstract

Most of the matter in the universe is in the form of dark matter, that has evaded detection so far. ALPs -- ultralight axionlike particles -- are a class of dark matter candidates that produce measurable signatures in the form of oscillating violations of discrete symmetries in nuclei. We report results from a search for an oscillating parity-odd time-reversal-odd nuclear Schiff moment of $^{153}$Eu ions in a crystal, which leads to constraints on ALP-gluon coupling strength across a wide band spanning eight decades in ALP mass.

Figures (4)

• Figure 1: a, Apparatus schematic. The ALP search experiment used laser absorption spectroscopy of the $^7F_0 \to {}^5D_0$ transition in a Eu:YSO crystal. b, Energy levels of $^{153}$Eu$^{3+}$:YSO. The ground ${}^7F_0$ and excited ${}^5D_0$ electronic states are connected by a $580nm$ optical transition. Within each electronic state, the 6 nuclear spin sublevels are split into 3 pairs of Kramers doublets, with opposite nuclear spin orientations for the two sublevels in each doublet. The $b-\bar{b}$ nuclear spin transition at $230kHz$ was probed using precision rf spectroscopy.
• Figure 2: a, Ramsey spectroscopy of the $b- \bar{b}$ transition for Eu$^{3+}$ ions of different polarizations $\pi=\pm1$. The vertical axis is the measured optical depth change between experiments with opposite spectroscopy pulse phase differences, $A(f,0^\circ) - A(f,180^\circ)$. Here the optical depth is defined as $\mathrm{OD}=-\log(P_T/P_M)$, where $P_T$ ($P_M$) is the optical power measured at the transmission (monitor) photodiode. The solid lines show fits to the theoretical Ramsey lineshape ramsey_molecular_1985 with center frequency, pulse area, and amplitude being the only free parameters. b, Phase scans of the $b- \bar{b}$ transition for different ion polarizations $\pi=\pm1$. The vertical axis is the optical depth measured with a fixed spectroscopy carrier frequency, $A(f=230.7kHz,\phi)$. The solid lines show sinusoidal fits. The Ramsey phase signals for $\pi=\pm1$ are identical to within the uncertainty.
• Figure 3: Best-fit oscillation power of the T-violation parameter $\delta f_d$ shown in blue. The peaks corresponds to technical noise frequencies and their aliased frequencies by experiment cycles. The ALP-free noise model is shown in yellow.
• Figure 4: The shaded region shows the 95%-confidence-level exclusion range on the ALP-gluon coupling from this work.