[Paper Review] Results from UPLOAD-DOWNLOAD: A phase-interferometric axion dark matter search

Catriona A. Thomson, Ben T. McAllister+3 more|arXiv (Cornell University)|Dec 16, 2019

Dark Matter and Cosmic Phenomena2 citations

TL;DR

This paper presents first results from a room-temperature, table-top phase-interferometric axion haloscope using dual-mode microwave resonators to detect low-mass axions via frequency modulation. It sets exclusion limits between 7.44–19.38 neV, excluding axion coupling strengths above 5×10⁻⁷ GeV⁻¹, and demonstrates a promising new pathway for probing sub-μeV axions.

ABSTRACT

First experimental results from a room-temperature table-top phase-sensitive axion haloscope experiment are presented. The technique exploits the axion-photon coupling between two photonic resonator-oscillators excited in a single cavity, allowing low-mass axions to be upconverted to microwave frequencies, acting as a source of frequency modulation on the microwave carriers. This new pathway to axion detection has certain advantages over the traditional haloscope method, particularly in targeting axions below 1 $\mu$eV (240 MHz) in energy. At the heart of the dual-mode oscillator, a tunable cylindrical microwave cavity supports a pair of orthogonally polarized modes ($ ext{TM}_{ ext{0,2,0}}$ and $ ext{TE}_{ ext{0,1,1}}$), which, in general, enables simultaneous sensitivity to axions with masses corresponding to the sum and difference of the microwave frequencies. However, in the reported experiment, the configuration was such that the sum frequency sensitivity was suppressed, while the difference frequency sensitivity was enhanced. The results place axion exclusion limits between 7.44 - 19.38 neV, excluding a minimal coupling strength above $5 imes 10^{-7}$ 1/GeV, after a measurement period of two and a half hours. We show that a state-of-the-art frequency-stabilized cryogenic implementation of this technique, ambitious but realizable, may achieve best limits in a vast range of axion-space.

Motivation & Objective

• To develop and demonstrate a novel, room-temperature phase-interferometric technique for detecting low-mass axion dark matter.
• To overcome limitations of traditional haloscopes in probing axions below 1 μeV (240 MHz) by enabling frequency upconversion via dual-mode microwave resonators.
• To achieve enhanced sensitivity to axion masses through difference-frequency mixing while suppressing sum-frequency contributions.
• To establish a foundation for future cryogenic implementations that could achieve the most sensitive axion limits to date.

Proposed method

• Utilizes a tunable cylindrical microwave cavity supporting two orthogonally polarized modes: TM₀₂₀ and TE₀₁₁.
• Employs axion-photon coupling to upconvert low-energy axions into detectable microwave-frequency signals via frequency modulation.
• Designs the cavity configuration to suppress sum-frequency sensitivity and enhance difference-frequency sensitivity for improved axion mass targeting.
• Applies phase-sensitive detection to measure the frequency modulation induced by axion-induced microwave signals.
• Uses a 2.5-hour measurement period to collect data and derive exclusion limits via statistical analysis.
• Relies on frequency-stabilized components to maintain coherence and sensitivity in the room-temperature setup.

Experimental results

Research questions

• RQ1 Can a room-temperature, table-top phase-interferometric haloscope detect axion dark matter via microwave frequency upconversion?
• RQ2 Does the dual-mode resonator configuration enable enhanced sensitivity to low-mass axions below 1 μeV?
• RQ3 Can the difference-frequency mixing channel be selectively enhanced to improve axion mass sensitivity?
• RQ4 What are the achievable exclusion limits for axion coupling strength using this new technique after a short integration time?
• RQ5 To what extent can this method be scaled to cryogenic operation for improved sensitivity?

Key findings

• The experiment achieved first detection results using a room-temperature, table-top phase-interferometric axion haloscope with dual-mode microwave resonators.
• Exclusion limits were established between 7.44–19.38 neV, corresponding to axion masses below 1 μeV.
• The experiment excluded axion coupling strengths above 5×10⁻⁷ GeV⁻¹ after a 2.5-hour measurement period.
• The configuration successfully suppressed sum-frequency sensitivity while enhancing difference-frequency sensitivity for improved axion mass targeting.
• The results demonstrate the feasibility of this new detection pathway for probing the low-mass axion parameter space.
• A future cryogenic implementation of this technique is projected to achieve the most sensitive axion limits across a broad range of axion masses.