Gapless dispersive continuum in a modulated quantum kagome antiferromagnet

Thennakoon, A.*; 横倉 涼雅*; Yang, Y.*; 梶本 亮一  ; 中村 充孝   ; 林 真弘*; 道岡 千城*; Chern, G.-W.*; Broholm, C.*; 植田 浩明*; Lee, S.-H.*

Thennakoon, A.*; Yokokura, Ryoga*; Yang, Y.*; Kajimoto, Ryoichi; Nakamura, Mitsutaka; Hayashi, Masahiro*; Michioka, Chishiro*; Chern, G.-W.*; Broholm, C.*; Ueda, Hiroaki*; Lee, S.-H.*

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 (, ) 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 CsRbKTiF where Ti (, ) 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 acquired at 1.5 K where the heat capacity is -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.