Prospects for axion dark matter searches at LISA-like interferometers

Axion or axionlike particles are one of the leading candidates for dark matter. Because of its tiny coupling with photons, axion dark matter in the background can induce distinct phase velocities for light with different parity, an effect known as birefringence. Here, we propose a modification to the polarization state of the interspacecraft laser link in Laser Interferometer Space Antenna (LISA)-like interferometers to make them sensitive to this birefringence effect. We discuss the prospects of using the Sagnac combinations to search for axion dark matter and derive the corresponding sensitivity. With this setup, we show that next-generation laser interferometers in space would have promising sensitivities on the axion-photon coupling with axion mass around <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>19</a:mn></a:mrow></a:msup><a:mo>−</a:mo><a:msup><a:mrow><a:mn>10</a:mn></a:mrow><a:mrow><a:mo>−</a:mo><a:mn>14</a:mn></a:mrow></a:msup><a:mtext> </a:mtext><a:mtext> </a:mtext><a:mi>eV</a:mi></a:mrow></a:math>.