July 28, 2025 - Scientists from the Department of Physics at the University of Oxford have found clear evidence of low-temperature spin dynamics in a Dirac spin liquid candidate. The findings have been published in Physical Review Letters.

While most magnetic materials settle into an ordered state below their critical temperatures, some materials, known as quantum spin liquids, do not, even at absolute zero. Quantum spin liquids have been of great interest in recent years as they may hold clues to future quantum technologies. In this study, the authors investigated a promising quantum spin liquid candidate, YbZn₂GaO₅, where the magnetic Yb ions are arranged in triangular layers and are connected by oxygen ions.

After synthesising the compound and then characterising it using very high magnetic fields in the Nicholas Kurti High Magnetic Field Laboratory, the group used the ISIS Pulsed Muon Source to implant muons directly into the triangular layers. Muons act as sensitive magnetic probes and ruled out any ordered state. Instead, the muon results reveal clear evidence for low-temperature spin dynamics, indicating that the system tunnels between the many degenerate ground states. The magnetic field dependence of the muon response helps to classify YbZ_n2GaO₅ as a particular type of theoretically predicted Dirac spin liquid.

'Our study found strong evidence for spin diffusion on a two-dimensional triangular lattice,' comments Dr Hank Wu, lead author and a postdoctoral research assistant at Oxford. 'We find that at low temperature the spin pairs are entangled by up to around 30 times the nearest neighbour spacing.'

'These experiments demonstrate how muon spectroscopy can be a powerful tool to study spin dynamics in quantum spin liquids – a long-sought state of matter in condensed matter physics,' adds Professor Stephen Blundell who leads the Muons and Magnets group at Oxford.