Electronic phenomena studied in the nordic countries

Physical realization of a new quantum spin liquid based on a novel frustration mechanism.

Not scheduled

15m

Max IV Lund

Speaker

Prof. Bella Lake (Helmholtz Zentrum Berlin für Materialien und Energie)

Description

Unlike conventional magnets where the magnetic moments are partially or completely static in the ground state, in a quantum spin liquid they remain in collective motion down to the lowest temperatures. The importance of this state is that it is coherent and highly entangled without breaking local symmetries. Such phenomena is usually sought in simple lattices where antiferromagnetic interactions and/or anisotropies favoring specific alignments of the magnetic moments, are frustrated by lattice geometries incompatible with such order. Despite an extensive search among such compounds, experimental realizations remain very few. Here we investigate the new spin-1/2 magnet, Ca10Cr7O28, which has a novel unexplored lattice with several isotropic interactions consisting of strong ferromagnetic and weaker antiferromagnetic couplings. Despite its unconventional structure and Hamiltonian, we show experimentally that it displays all the features expected of a quantum spin liquid. Bulk properties measurements, neutron scattering and muon spin relaxation reveal coherent spin dynamics in the ground state, the complete absence of static magnetism and diffuse spinon excitations. Pseudo-Fermion renormalization group calculations verify that the Hamiltonian of Ca10Cr7O28 supports a dynamical ground state which furthermore is robust to significant variations of the exchange constants.