The thermal Hall effect of spin excitations in a Kagome magnet

2015/02/19 by Max Hirschberger, Robin Chisnell, Young S. Lee +1 · 1 citation
Physics and Astronomy · #cond-mat.str-el

paper · pdf · doi:10.1103/physrevlett.115.106603

published as Phys. Rev. Lett. 115, 106603 (2015) · 6 pages, 3 figures

arxiv created 2015/02/19 · arxiv updated 2015/09/09

Abstract

At low temperatures, the thermal conductivity of spin excitations in a magnetic insulator can exceed that of phonons. However, because they are charge neutral, the spin waves are not expected to display a thermal Hall effect in a magnetic field. Recently, this semiclassical notion has been upended in quantum magnets in which the spin texture has a finite chirality. In the Kagome lattice, the chiral term generates a Berry curvature. This results in a thermal Hall conductivity κ_xy that is topological in origin. Here we report observation of a large κ_xy in the Kagome magnet Cu(1-3, bdc) which orders magnetically at 1.8 K. The observed κ_xy undergoes a remarkable sign-reversal with changes in temperature or magnetic field, associated with sign alternation of the Chern flux between magnon bands. We show that thermal Hall experiments probe incisively the effect of Berry curvature on heat transport.

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