- Open Access
NMR evidence for interlayer-modulated charge order and a first-order low-temperature transition in
Phys. Rev. B 112, 235123 – Published 8 December, 2025
DOI: https://doi.org/10.1103/91c9-z267
Abstract
Charge order in the kagome superconductor exhibits a complex three-dimensional organization and intermediate-temperature anomalies whose bulk character has remained unsettled. We use orientation-dependent NMR as a site-selective probe to determine the stacking of the charge density wave (CDW) state and its thermal evolution. Below , the field-linear splitting of the central transition together with the anisotropy of the Knight shift tensor identify an interlayer-modulated CDW whose local environments are consistent with a four-layer stacking with mixed trihexagonal/Star-of-David distortions, in agreement with synchrotron x-ray determinations. For comparison, serves as a reference exhibiting a uniform trihexagonal stacking, allowing us to isolate features unique to the state in . With , the quadrupolar satellites through the intermediate temperature scale near reorganize into two well-resolved electric-field-gradient manifolds that coexist over a finite interval; their relative spectral weights interchange on cooling while the total integrated satellite intensity remains conserved and within each manifold is nearly temperature independent. The coexistence without critical broadening, together with conserved intensity, provides bulk evidence consistent with a first-order charge-order transition near . Our measurements do not resolve whether this lower-temperature transition corresponds to a distinct in-plane order or a reorganization of the state; rather, they delimit this window and provide bulk, site-resolved constraints that connect prior reported anomalies to a thermodynamic first-order transition.
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