Forschung: Eine Quanten-Spinflüssigkeit auf einem neuen dreidimensiona­len Gitter

Quantum spin liquid materials differ significantly from conventional magnetic materials because quantum fluctuations dominate the magnetic interactions. Due to the geometric constraints of the crystal lattice, spins cannot all "freeze" together in a ground state instead they are forced to fluctuate, even at temperatures close to absolute zero. Quantum spin liquids are rare and have so far been found mainly in two-dimensional magnetic systems. An experimental investigation of PbCuTe₂O₆ with neutron scattering measurements revealed a three-dimensional spectrum, due to a new so called hyper-hyperkagome lattice where the excitations appeared broad and diffuse as is typical of spin liquid behaviour. The experimental data was then compared to theoretical studies of the spectrum, using the Hamiltonian for this compound extracted from density functional calculations. The theory found that the Hamiltonian does not support long-range magnetic order -  another key feature of a quantum spin liquid - and could accurately predict the observed spectrum. Three-dimensional spin liquids are very rare and current examples are confined mostly to the pyrochlore and hyperkagome lattices, thus these results are exciting because they reveal a new type of three-dimensional lattice capable of supporting isotropic spin liquid behaviour.

S. Chillal, Y. Iqbal, H. O. Jeschke, J. A. Rodriguez-Rivera, R. Bewley, P. Manuel, D. Khalyavin, P. Steffens, R. Thomale, A. T. M. N. Islam, J. Reuther, B. Lake,
Evidence for a three-dimensional quantum spin liquid in PbCuTe₂O₆,
Nat. Commun. 11, 2348 (2020)