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Abstract Geometrically frustrated kagome lattices are raising as novel platforms to engineer correlated topological electron flat bands that are prominent to electronic instabilities. Here, we demonstrate a phonon softening at thek_z = πplane in ScV₆Sn₆. The low energy longitudinal phonon collapses at ~98 K andq = $$\frac{1}{3}\frac{1}{3}\frac{1}{2}$$ $\frac{1}{3}\frac{1}{3}\frac{1}{2}$due to the electron-phonon interaction, without the emergence of long-range charge order which sets in at a different propagation vectorq_CDW = $$\frac{1}{3}\frac{1}{3}\frac{1}{3}$$ $\frac{1}{3}\frac{1}{3}\frac{1}{3}$. Theoretical calculations corroborate the experimental finding to indicate that the leading instability is located at$$\frac{1}{3}\frac{1}{3}\frac{1}{2}$$ $\frac{1}{3}\frac{1}{3}\frac{1}{2}$of a rather flat mode. We relate the phonon renormalization to the orbital-resolved susceptibility of the trigonal Sn atoms and explain the approximately flat phonon dispersion. Our data report the first example of the collapse of a kagome bosonic mode and promote the 166 compounds of kagomes as primary candidates to explore correlated flat phonon-topological flat electron physics. 

This study investigates the processing of Turkish negative polarity items (NPIs) using a self-paced reading experiment with end-of-sentence acceptability judgements. Our participants included adult Turkish monolinguals, as well as Turkish-German early (i.e. heritage speakers) and late bilinguals. We explored whether intrusion effects from illusory NPI licensors extended to bilingual Turkish speakers who had acquired German either early or late in their lives. Stimuli included 30 sets of sentences in six experimental conditions, with the presence of both an NPI and of a suitable licenser (verb negation) systematically manipulated. Our results indicate that bilingual Turkish readers show intrusion effects in their processing of NPIs. Our findings suggest that the structural conditions for NPI licensing in Turkish might be degraded or less stable in heritage bilinguals.