Thermal Hall conductivity in the frustrated pyrochlore magnet Tb2Ti2O7

Understand

In a ferromagnet, the spin excitations are the well-studied magnons.

• In frustrated quantum magnets, long-range magnetic order fails to develop despite a large exchange coupling between the spins.
• In contrast to the magnons in conventional magnets, their spin excitations are poorly understood.
• Are they itinerant or localized? Here we show that the thermal Hall conductivity $\kappa_{xy}$ provides a powerful probe of spin excitations in the "quantum spin ice" pyrochlore Tb$_2$Ti$_2$O$_7$.