Strongly Entangled Kondo and Kagome Lattices and the Emergent Magnetic Ground State in Heavy-Fermion Kagome Metal YbV6Sn6

Applying angle-resolved photoemission spectroscopy and density functional theory calculations, we present compelling spectroscopic evidence demonstrating the intertwining and mutual interaction between the Kondo and kagome sublattices in heavy-fermion intermetallic compound <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mrow><a:mrow><a:msub><a:mrow><a:mi>YbV</a:mi></a:mrow><a:mrow><a:mn>6</a:mn></a:mrow></a:msub></a:mrow><a:mrow><a:msub><a:mrow><a:mi>Sn</a:mi></a:mrow><a:mrow><a:mn>6</a:mn></a:mrow></a:msub></a:mrow></a:mrow></a:math>. We reveal the Yb <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mrow><c:mn>4</c:mn><c:mi>f</c:mi></c:mrow></c:math>-derived states near the Fermi level, along with the presence of bulk kagome bands and topological surface states. We unveil strong interactions between the <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mrow><e:mn>4</e:mn><e:mi>f</e:mi></e:mrow></e:math> and itinerant electrons, where the kagome bands hosting the Dirac fermions and van Hove singularities predominate. Such findings are well described using a <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"><g:mrow><g:mi>c</g:mi><g:mtext>−</g:mtext><g:mi>f</g:mi></g:mrow></g:math> hybridization model. On the other hand, our systematic characterization of magnetic properties demonstrates an unusually enhanced antiferromagnetic ordering, where the kagome-derived van Hove singularities near <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"><i:msub><i:mi>E</i:mi><i:mi>F</i:mi></i:msub></i:math> play a vital role in determining the unconventional nature of the Ruderman-Kittel-Kasuya-Yosida interaction and Kondo coupling. These unique kagome-state-mediated exchange interactions have never been reported before and could lead to a novel phase diagram and various quantum critical behaviors in <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:mrow><k:msub><k:mrow><k:mi>YbV</k:mi></k:mrow><k:mrow><k:mn>6</k:mn></k:mrow></k:msub></k:mrow><k:mrow><k:msub><k:mrow><k:mi>Sn</k:mi></k:mrow><k:mrow><k:mn>6</k:mn></k:mrow></k:msub></k:mrow></k:math> and its siblings. Our results not only expand the family of exotic quantum phases entangled with kagome structure to the strongly correlated regime, but also establish <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:mrow><m:mrow><m:msub><m:mrow><m:mi>YbV</m:mi></m:mrow><m:mrow><m:mn>6</m:mn></m:mrow></m:msub></m:mrow><m:mrow><m:msub><m:mrow><m:mi>Sn</m:mi></m:mrow><m:mrow><m:mn>6</m:mn></m:mrow></m:msub></m:mrow></m:mrow></m:math> as an unprecedented platform to explore unconventional many-body physics beyond the standard Kondo picture.