Dimensional reduction and incommensurate dynamic correlations in the [Formula: see text] triangular-lattice antiferromagnet Ca(3)ReO(5)Cl(2)

The observation of spinon excitations in the [Formula: see text] triangular antiferromagnet Ca(3)ReO(5)Cl(2) reveals a quasi-one-dimensional (1D) nature of magnetic correlations, in spite of the nominally 2D magnetic structure. This phenomenon is known as frustration-induced dimensional reduction. Here, we present high-field electron spin resonance spectroscopy and magnetization studies of Ca(3)ReO(5)Cl(2), allowing us not only to refine spin-Hamiltonian parameters, but also to investigate peculiarities of its low-energy spin dynamics. We argue that the presence of the uniform Dzyaloshinskii-Moriya interaction (DMI) shifts the spinon continuum in momentum space and, as a result, opens a zero-field gap at the Γ point. We observed this gap directly. The shift is found to be consistent with the structural modulation in the ordered state, suggesting this material as a perfect model triangular-lattice system, where a pure DMI-spiral ground state can be realized.