Gapless dispersive continuum in a modulated quantum kagome antiferromagnet.

Thennakoon, Asiri; Yokokura, Ryouga; Yang, Yang; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Hayashi, Masahiro; Michioka, Chishiro; Chern, Gia-Wei et al. · Nat Commun · 2025

basic_science · Level V

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Abstract

The pursuit of quantum spin liquid (QSL) states in condensed matter physics has drawn attention to kagome antiferromagnets (AFM) where a two-dimensional corner-sharing network of triangles frustrates conventional magnetic orders. While quantum kagome AFMs based on Cu<sup>2+</sup> (3d<sup>9</sup>, s = ½) ions have been extensively studied, there is so far little work beyond copper-based systems. Here we present our bulk magnetization, specific heat and neutron scattering studies on single crystals of a new titanium fluorides Cs<sub>8</sub>RbK<sub>3</sub>Ti<sub>12</sub>F<sub>48</sub> where Ti<sup>3+</sup> (3d<sup>1</sup>, s = ½) ions form a modulated quantum kagome antiferromagnet that does not order magnetically down to 1.5 K. Our comprehensive map of the dynamic response function <math xmlns="http://www.w3.org/1998/Math/MathML"><mi>S</mi> <mrow><mo>(</mo> <mrow><mi>Q</mi> <mo>,</mo> <mi>ℏ</mi> <mi>ω</mi></mrow> <mo>)</mo></mrow> </math> acquired at 1.5 K where the heat capacity is T-linear reveals a dispersive continuum emanating from soft lines that extend along (100). The data indicate fractionalized spinon-like excitations with quasi-one-dimensional dispersion within a quasi-two-dimensional spin system.