A significant obstacle to the realisation of quantum computing is the fragility of the qubit, where information would be stored. Developing a system that can store information and remain robust to interference is key to having fault-tolerant quantum computations.
Quantum spin liquids (QSLs) occur when the magnetic moments of a material become entangled but remain disordered even at absolute zero. They can form stable complex topologies, making them a potential candidate for quantum computing materials.
Dr Andrej Zorko has been awarded the Science Impact Award this year for his work on one particular QSL found in neodymium heptatantalate, NdTa7O19. This compound was anticipated to behave as a QSL, after a theoretical prediction made seventy years ago, but, until recently, this had not been experimentally confirmed.
Using a combination of muon spectroscopy on MuSR, inelastic neutron scattering (INS) on MARI and neutron diffraction on WISH, as well as other experimental techniques in the laboratory and at large-scale facilities around the world, the team were able to show for the first time that a QSL is formed in NdTa7O19.
Although a few other QSL candidates have been characterised, this compound is the first of its kind: a triangular spin lattice with dominant Ising antiferromagnetic nearest-neighbour spin correlations.
Using INS, they were able to confirm that the magnetic species had effective spin 1/2 at low temperatures. They then used neutron diffraction to characterise the ground state, finding that there was no magnetic ordering even down at the lowest experimental temperature while spin correlations were found to develop. Following up these studies with experiments on MuSR meant they were able to confirm the absence of magnetic order, and show that there were spin dynamics present in the ground state, revealing the quantum nature of the ground state.
His group's results show the community that the family of rare-earth heptatantalates is a potential source of candidate materials for quantum computing applications.
Related publication: The Ising triangular-lattice antiferromagnet neodymium heptatantalate as a quantum spin liquid candidate, Nature Materials, 21, 416–422 (2022), DOI: 10.1038/s41563-021-01169-y