Charge-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>4</mml:mn><mml:mi>e</mml:mi></mml:mrow></mml:math> and Charge-<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:mn>6</mml:mn><mml:mi>e</mml:mi></mml:mrow></mml:math> Flux Quantization and Higher Charge Superconductivity in Kagome Superconductor Ring Devices

Abstract

The flux quantization is a key indication of electron pairing in superconductors. For example, the well-known <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mi>h</a:mi><a:mo>/</a:mo><a:mn>2</a:mn><a:mi>e</a:mi></a:mrow></a:math> flux quantization is considered strong evidence for the existence of charge-<c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>2</c:mn><c:mi>e</c:mi></c:mrow></c:math>, two-electron Cooper pairs. Here we report evidence for multicharge flux quantization in mesoscopic ring devices fabricated using the transition-metal kagome superconductor <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:msub><e:mrow><e:mi>CsV</e:mi></e:mrow><e:mn>3</e:mn></e:msub><e:msub><e:mrow><e:mi>Sb</e:mi></e:mrow><e:mn>5</e:mn></e:msub></e:mrow></e:math>. We perform systematic magnetotransport measurements and observe unprecedented quantization of magnetic flux in units of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi>h</g:mi><g:mo>/</g:mo><g:mn>4</g:mn><g:mi>e</g:mi></g:mrow></g:math> and <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:mrow><i:mi>h</i:mi><i:mo>/</i:mo><i:mn>6</i:mn><i:mi>e</i:mi></i:mrow></i:math> in magnetoresistance oscillations. Specifically, at low temperatures, magnetoresistance oscillations with period <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:mi>h</k:mi><k:mo>/</k:mo><k:mn>2</k:mn><k:mi>e</k:mi></k:mrow></k:math> are detected, as expected from the flux quantization for charge-<m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:mn>2</m:mn><m:mi>e</m:mi></m:mrow></m:math> superconductivity. We find that the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:mrow><o:mi>h</o:mi><o:mo>/</o:mo><o:mn>2</o:mn><o:mi>e</o:mi></o:mrow></o:math> oscillations are suppressed and replaced by resistance oscillations with <q:math xmlns:q="http://www.w3.org/1998/Math/MathML" display="inline"><q:mrow><q:mi>h</q:mi><q:mo>/</q:mo><q:mn>4</q:mn><q:mi>e</q:mi></q:mrow></q:math> periodicity when the temperature is increased. Increasing the temperature further suppresses the <s:math xmlns:s="http://www.w3.org/1998/Math/MathML" display="inline"><s:mrow><s:mi>h</s:mi><s:mo>/</s:mo><s:mn>4</s:mn><s:mi>e</s:mi></s:mrow></s:math> oscillations, and robust resistance oscillations with <u:math xmlns:u="http://www.w3.org/1998/Math/MathML" display="inline"><u:mrow><u:mi>h</u:mi><u:mo>/</u:mo><u:mn>6</u:mn><u:mi>e</u:mi></u:mrow></u:math> periodicity emerge as evidence for charge-<w:math xmlns:w="http://www.w3.org/1998/Math/MathML" display="inline"><w:mrow><w:mn>6</w:mn><w:mi>e</w:mi></w:mrow></w:math> flux quantization. Our observations provide the first experimental evidence for the existence of multicharge flux quanta and emergent quantum matter exhibiting higher-charge superconductivity in the strongly fluctuating region above the charge-<y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:mrow><y:mn>2</y:mn><y:mi>e</y:mi></y:mrow></y:math> Cooper pair condensate, revealing new insights into the intertwined and vestigial electronic order in kagome superconductors. Published by the American Physical Society 2024

Topics & Concepts