Intertwined charge and spin density waves in a topological kagome material

Using neutrons and x rays we show the topological kagome antiferromagnet <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:msub><a:mi>Mn</a:mi><a:mn>3</a:mn></a:msub><a:mi>Sn</a:mi></a:mrow></a:math> for <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>T</b:mi><b:mo><</b:mo><b:mn>285</b:mn><b:mspace width="0.28em"/><b:mi mathvariant="normal">K</b:mi></b:mrow></b:math> forms a homogeneous spin and charge ordered state comprising a longitudinally polarized spin density wave with wave vector <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:msub><e:mi mathvariant="bold">k</e:mi><e:mi>β</e:mi></e:msub><e:mo>=</e:mo><e:msub><e:mi>k</e:mi><e:mi>β</e:mi></e:msub><e:mover accent="true"><e:mi mathvariant="bold">c</e:mi><e:mo>̂</e:mo></e:mover></e:mrow></e:math>, a helical modulated version of the room temperature antichiral magnetic order with <i:math xmlns:i="http://www.w3.org/1998/Math/MathML"><i:mrow><i:msub><i:mi mathvariant="bold">k</i:mi><i:mi>χ</i:mi></i:msub><i:mo>=</i:mo><i:msub><i:mi>k</i:mi><i:mi>χ</i:mi></i:msub><i:mover accent="true"><i:mi mathvariant="bold">c</i:mi><i:mo>̂</i:mo></i:mover></i:mrow></i:math>, and charge density waves with wave vectors <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"><m:mrow><m:mn>2</m:mn><m:msub><m:mi mathvariant="bold">k</m:mi><m:mi>β</m:mi></m:msub><m:mo>,</m:mo><m:mn>2</m:mn><m:msub><m:mi mathvariant="bold">k</m:mi><m:mi>χ</m:mi></m:msub></m:mrow></m:math>, and <p:math xmlns:p="http://www.w3.org/1998/Math/MathML"><p:mrow><p:msub><p:mi mathvariant="bold">k</p:mi><p:mi>β</p:mi></p:msub><p:mo>+</p:mo><p:msub><p:mi mathvariant="bold">k</p:mi><p:mi>χ</p:mi></p:msub></p:mrow></p:math>. Though <s:math xmlns:s="http://www.w3.org/1998/Math/MathML"><s:msub><s:mi mathvariant="bold">k</s:mi><s:mi>χ</s:mi></s:msub></s:math> and <u:math xmlns:u="http://www.w3.org/1998/Math/MathML"><u:msub><u:mi mathvariant="bold">k</u:mi><u:mi>β</u:mi></u:msub></u:math> coincide for <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"><w:mrow><w:mn>200</w:mn><w:mspace width="4pt"/><w:mi mathvariant="normal">K</w:mi><w:mo><</w:mo><w:mi>T</w:mi><w:mo><</w:mo><w:mn>230</w:mn><w:mspace width="0.28em"/><w:mi mathvariant="normal">K</w:mi></w:mrow></w:math>, they exhibit distinct continuous <bb:math xmlns:bb="http://www.w3.org/1998/Math/MathML"><bb:mrow><bb:mi>T</bb:mi><bb:mspace width="4pt"/><bb:mi>dependencies</bb:mi></bb:mrow></bb:math> before locking to commensurate values of <db:math xmlns:db="http://www.w3.org/1998/Math/MathML"><db:mrow><db:msub><db:mi mathvariant="bold">k</db:mi><db:mi>β</db:mi></db:msub><db:mo>=</db:mo><db:mfrac><db:mn>1</db:mn><db:mn>12</db:mn></db:mfrac><db:msup><db:mrow><db:mi mathvariant="bold">c</db:mi></db:mrow><db:mo>*</db:mo></db:msup></db:mrow></db:math> and <gb:math xmlns:gb="http://www.w3.org/1998/Math/MathML"><gb:mrow><gb:msub><gb:mi mathvariant="bold">k</gb:mi><gb:mi>χ</gb:mi></gb:msub><gb:mo>=</gb:mo><gb:mfrac><gb:mn>5</gb:mn><gb:mn>48</gb:mn></gb:mfrac><gb:msup><gb:mrow><gb:mi mathvariant="bold">c</gb:mi></gb:mrow><gb:mo>*</gb:mo></gb:msup></gb:mrow></gb:math> at <jb:math xmlns:jb="http://www.w3.org/1998/Math/MathML"><jb:mrow><jb:mi>low</jb:mi><jb:mspace width="4pt"/><jb:mi>T</jb:mi></jb:mrow></jb:math>. Density functional theory indicates this complex modulated state may be associated with the nesting of Fermi surfaces from correlated flat kagome bands, which host Weyl nodes that are annihilated as it forms. Published by the American Physical Society 2024