Enhanced thermal Hall conductivity below 1 Kelvin in the pyrochlore magnet Yb${}_2$Ti${}_2$O${}_7$

Abstract

In this letter, we report the gigantic thermal Hall effect ${\kappa }_{xy}$ in the low-field correlated-paramagnetic state of the frustrated pyrochlore Yb${}_2$Ti${}_2$O${}_7$. We observed a record magnitude for the thermal Hall angle in an insulator, $\left|{\kappa }_{xy}\right|/{\kappa }_{xx}\sim 2\%$. The signal onsets at $T\sim 3$K and is severely weakened around the transition to canted ferromagnetic order at $T_{\text{CFM}}=0.275$K. Besides the large ${\kappa }_{xy}>0$ of the fluctuating regime, a sign change towards negative ${\kappa }_{xy}$ occurs at the lowest temperatures and in moderate field, where sharp magnon excitations appear in the inelastic neutron scattering spectra. We analyze the magnon-Hall signal and its suppression with field semi-quantitatively. A contribution of phonon skew scattering to ${\kappa }_{xy}$ is ruled out by a comparison of ${\kappa }_{xx}$ for Tb-, Yb-, and Y-based rare earth pyrochlore titanates. These results represent the first report of non-vanishing ${\kappa }_{xy}$ measured in a dilution refrigerator ($T<0.29$K).

arXiv comment13 pages, 4 figures

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Cited by in corpus (4)

• Possible itinerant excitations and quantum spin state transitions in the effective spin-1/2 triangular-lattice antiferromagnet Na${}_2$BaCo(PO${}_4$)${}_2$
• Thermal Hall effects in quantum magnets
• Extrinsic phonon thermal Hall transport from Hall viscosity
• Orientation Dependence of the Magnetic Phase Diagram of Yb${}_2$Ti${}_2$O${}_7$