Resonant electric probe to axionic dark matter

The oscillating light axion field is known as wave dark matter. We propose an LC (inductor-capacitor)-resonance enhanced detection of the narrow band electric signals induced by the axion dark matter using a solenoid magnet facility. We provide full 3D electromagnetic simulation results for the signal electric field. The electric signal is enhanced by the high $Q$-factor of a resonant LC circuit and then amplified and detected by the state-of-the-art cryogenic electrical transport measurement technique. The cryogenic amplifier noise is the dominant noise source in the proposed detection system. We estimate that the detection system can have a promising sensitivity to axion dark matter with mass below ${10}^{-6}\mathrm{eV}$. The projected sensitivities improve with the size of the magnetic field, and the electric signal measurement can be potentially sensitive to the quantum chromodynamics (QCD) axion with $g_{a\gamma }\sim {10}^{-16}{\mathrm{GeV}}^{-1}$ around $m_a\sim {10}^{-8}\mathrm{eV}$, with a multimeter scale magnetized region. This limit is around five orders of magnitude below the current constraint from the cosmic rays.

Figure 1

Validation 2D plots by the electromagnetic simulation to compare with analytic ansatz. $E_z$ is in the unit of $V/m$, $R$ is the radius of the solenoid magnetic field and $\lambda =2\pi /m_a$.

Figure 2

Illustration for the experimental scheme. The voltage signal from parallel plates inside a solenoid magnetic field is enhanced by a resonant LCR circuit and then fed to amplifiers. The LCR is under $T_c\ll 1\mathrm{K}$ to reduce thermal noise.

Figure 3

3D simulations in a magnetic solenoid with conducting plates. The detector size is $R=1m,d=1m$. $E_z$ and $E_r$ are in the unit of $V/m$. The thick conducting plates are chosen to show well-separated upper and bottom surfaces. The top two plots are for $m_a={10}^{-8}\mathrm{eV}$ and the bottom two are for $m_a={10}^{-10}\mathrm{eV}$.

Figure 4

Projected parameter space of sensitivity at benchmark setups (dotted curves), assuming $B_0=14\mathrm{T}$ and one week’s observation time at each frequency. The CAST exclusion limit [66] and recent constraints from resonance cavity experiments (stripes, right), cosmic rays (left, see, e.g., [67]), and noncavity narrow-band experiments, such as BASE [42], ADMX-SLIC [40] and DMRadio-${\mathrm{m}}^3$ (projected sensitivity) [68] are shown for comparison. The frequency axis is transformed via $f=m_a/2\pi \simeq 2.4\mathrm{GHz}(m_a/{10}^{-5}\mathrm{eV})$.

Figure 5

Phase difference $\mathrm{mod}(\mathrm{\Delta }\varphi /\pi ,2)$ between the charge and voltage difference on the parallel plates, in terms of $\omega R$.