Origin of enhanced charge density wave in the kagome superconductor CsV3−xMoxSb5

The topological kagome superconductor ${\mathrm{CsV}}_{3}{\mathrm{Sb}}_{5}$ exhibits rich quantum phenomenology of correlated electronic phases including unconventional charge order and superconductivity. Understanding how the singularities inherent to the kagome lattice are linked to the observed many-body phases is a topic of great interest. Here, by using Shubnikov--de Haas oscillation measurements, we report the detailed evolution of electronic band structures in ${\mathrm{CsV}}_{3\ensuremath{-}x}{\mathrm{Mo}}_{x}{\mathrm{Sb}}_{5}$ single crystals, where Mo substitution causes a suppression of superconductivity and an enhanced charge density wave. The obvious decrease of oscillation frequency $({F}_{\ensuremath{\beta}})$ corresponding to the nontrivial band from 72 to 59 T and smaller cyclotron effective mass $(\ensuremath{\sim}0.069{m}_{e})$ reveal that the van Hove singularities from the vanadium orbitals near $M$ are abnormally lifted and promote the nesting condition for the charge density wave. Meanwhile, the electric conduction changes from a hole-dominated multiband feature to a single electron band feature and the anomalous Hall effect becomes stronger. In conjunction with the simple schematics of band structures, the promoted Fermi-surface nesting is dominant in the unusual enhanced charge density wave, offering insight to comprehend the delicate interaction between the intertwined orders in this kagome system.