Regensburg 2022 – scientific programme
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TT: Fachverband Tiefe Temperaturen
TT 5: Frustrated Magnets – Spin Liquids
TT 5.3: Talk
Monday, September 5, 2022, 15:45–16:00, H10
Thermal conductivity of a new quantum Kagome antiferromagnet YCu3(OH)6.5Br2.5 — •Xiaochen Hong1,2, Mahdi Behnami2, Long Yuan3, Boqiang Li3, Wolfram Brenig4, Bernd Büchner2, Yuesheng Li3, and Christian Hess1,2 — 1Bergische Universität Wuppertal — 2IFW-Dresden — 3Huazhong University of Sci. and Tech., Wuhan, China — 4TU Braunschweig
Herbertsmithite ZnCu3(OH)6Cl2 has long been studied as the archetypal quantum Kagome antiferromagnet whose ground state is anticipated to be a spin liquid. However, there is no consensus on the ground state properties of Herbertsmithite, in particular whether a spin gap exist or not, due to its Cu/Zn site mixing effect that distorts the Kagome plane.
Here we report low temperature thermal conductivity measurements of a newly synthesized quantum Kagome antiferromagnet YCu3(OH)6.5Br2.5. We observe a downwards deviation of its thermal conductivity κ from a standard phononical power-law temperature dependence beyond a characteristic temperature T* and a systematic enhancement of this deviation upon application of a magnetic field. Furthermore, up to 16 T no residual κ/T occurs. Our findings imply that the thermal conductivity is dominated by phonons in the mK range, excluding itinerant gapless excitations contributing to it. We interpret the suppression of κ in magnetic field as a consequence of enhanced scattering of the phonons off magnetic fluctuations beyond T*. Our analysis favors a small gap in the magnetic excitations, which is be suppressed by the magnetic field.