Magnetic chirality of the spin triplet in the spin-ladder compound Sr14Cu24O41as seen via polarized inelastic neutron scattering

Abstract

We report the direct observation by polarized inelastic neutron scattering experiments at low fields (3.5 T) of the splitting of the spin triplet of magnetic excitations in the response associated with the ladders in the composite cuprate Sr${}_{14}$Cu${}_{24}$O${}_{41}$. By conveniently choosing the magnetic field configuration and by making use of the spin chirality of the excitations, the splitting can be observed at relatively low fields. In this way, resonant excitations can be separated from the remainder of magnetic and phonon excitations at high temperatures. In Sr${}_{14}$Cu${}_{24}$O${}_{41}$, the 32-meV gapped mode vanishes above $~$200 K, close to the hole-crystal melting temperature previously observed by resonant x-ray and neutron diffraction.