When atoms are arranged in corner-sharing triangles, a geometrically special structure known as a kagome lattice is formed, in which exotic electronic and magnetic properties are predicted. Examples include superconductivity, relativistic electron motion, and quantum entanglement of electron spin. Such properties are sensitive to the concentration of electrons in the crystal, so tuning that concentration is crucial for not only exploring and controlling the exotic properties but also understanding the underlying physical mechanisms. Here, we develop a convenient means to introduce electron carriers into a newly discovered superconductor with a kagome lattice and realize a drastic change in the electronic properties.

We focus on the kagome material ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$, in which superconductivity coexists with a spatial modulation of electron charge density called a charge-density wave. To introduce additional charge carriers, we dose cesium atoms onto the crystal surface. By monitoring the evolution of the electronic structure using angle-resolved photoemission spectroscopy, we demonstrate a heavy electron-doping effect, which has never been realized in this material’s family. We further show complete suppression of the charge-density wave, triggered by an unusual orbital-selective change in the electronic structure. This finding suggests that the electrons in multiple atomic orbitals are simultaneously involved in the occurrence of the charge-density wave.

Our observation lays a foundation for understanding the nature of charge-density waves and their interplay with superconductivity in ${\mathrm{CsV}}_3{\mathrm{Sb}}_5$. In addition, our carrier-tuning technique would be useful to explore superconductivity at even higher temperatures.