Electron-Correlation-Assisted Charge Stripe Order in a Kagome Superconductor

A central mystery in high-temperature cuprate superconductors is the coexistence of multiple exotic orders, which is presumably associated with strong electronic correlation. The ongoing interest in this enigmatic phenomenon is further energized when similar electronic orders and states emerge and coexist in less correlated kagome superconductors. Here, by utilizing angle-resolved photoemission spectroscopy (ARPES), nuclear magnetic resonance (NMR) spectroscopy, scanning tunneling microscopy (STM) and first-principles calculations, we reveal the sudden emergence of a distinct short-range charge stripe order in Sn-doped <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:msub> <a:mi>CsV</a:mi> <a:mn>3</a:mn> </a:msub> <a:msub> <a:mi>Sb</a:mi> <a:mn>5</a:mn> </a:msub> </a:mrow> </a:math> kagome superconductors when the long-range <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"> <c:mrow> <c:mn>2</c:mn> <c:mo>×</c:mo> <c:mn>2</c:mn> </c:mrow> </c:math> charge density wave order in pristine <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"> <e:mrow> <e:msub> <e:mi>CsV</e:mi> <e:mn>3</e:mn> </e:msub> <e:msub> <e:mi>Sb</e:mi> <e:mn>5</e:mn> </e:msub> </e:mrow> </e:math> is suppressed. This short-range stripe order features a modulation vector of approximately <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mrow> <g:mrow> <g:mn>1</g:mn> <g:mo>/</g:mo> <g:mn>3</g:mn> </g:mrow> </g:mrow> </g:math> along one of the three lattice directions, induces remarkable quasiparticle scattering between the original quasi-1D kagome <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mi>d</i:mi> </i:math> bands and their replica of folding, and clearly suppresses the electron density of states at the Fermi level. Our first-principles calculations reveal that <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"> <k:mrow> <k:mn>3</k:mn> <k:mo>×</k:mo> <k:mn>1</k:mn> </k:mrow> </k:math> supermodulation represents a hidden secondary instability in pristine <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"> <m:mrow> <m:msub> <m:mi>CsV</m:mi> <m:mn>3</m:mn> </m:msub> <m:msub> <m:mi>Sb</m:mi> <m:mn>5</m:mn> </m:msub> </m:mrow> </m:math> . This instability is further enhanced by in-plane chemical pressure induced by Sn substitution, and coupled to the electronic correlation, leading to a unique charge stripe order in the system. As such, our results reveal a new route toward emergent electronic orders via cooperative interactions between the lattice and electronic degrees of freedom.