Axion Dark Matter Search with Sensitivity near the Kim-Shifman-Vainshtein-Zakharov Benchmark Using the TM020 Mode

Axions, originally proposed to resolve the <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>C</a:mi><a:mi>P</a:mi></a:mrow></a:math> problem in the strong interaction, remain a leading dark matter candidate. While cavity haloscopes offer the most sensitive technique for detecting axions, searches have largely been limited to masses below <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>10</c:mn><c:mtext> </c:mtext><c:mtext> </c:mtext><c:mi>μeV</c:mi></c:mrow></c:math>. We report a sensitive search for axion dark matter with masses around <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mn>21</e:mn><e:mtext> </e:mtext><e:mtext> </e:mtext><e:mi>μeV</e:mi></e:mrow></e:math>, utilizing the <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:msub><g:mrow><g:mi>TM</g:mi></g:mrow><g:mrow><g:mn>020</g:mn></g:mrow></g:msub></g:mrow></g:math> mode of a cylindrical cavity equipped with an innovative tuning mechanism. Our search achieved a sensitivity of <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mn>1.7</i:mn><i:mo>×</i:mo></i:math> the Kim-Shifman-Vainshtein-Zakharov benchmark over a 100-MHz range, representing a significant advance in this mass range. These results demonstrate that higher-order modes provide a viable strategy for extending haloscope searches into previously unexplored higher-mass regions.