Speaker
Description
Many magnetically frustrated systems exhibit what is known as persistent spin dynamics (PSD) in $\mu$SR experiments, the origin of which has remained mysterious since their discovery in the 1990s. As the temperature is lowered, the muon-spin relaxation rate rises (as would be expected for the slowing-down of spin fluctuations) but this rate then saturates at low temperature, the low-temperature fluctuations being interpreted as PSD. To explain this phenomenon, we describe how muons can couple to singlet states and illustrate this with experimental data taken on Tm$_2$Ti$_2$O$_7$. The key idea is that the hyperfine interaction, usually neglected in treatments of electronic magnetism, provides a route in which excited states can be mixed into the ground state, and this new state can couple to the "quantum muon'' [1]. This mechanism lies behind the effect found in some quantum spin ice compounds [2], but here it is not based on the distortion effects surrounding the muon. We will show how this idea can be extended to understand the way muons couple to a variety of systems exhibiting highly frustrated magnetism, as well as to dynamical problems more generally [3].
[1] S. J. Blundell, J. Phys.: Conf. Ser. 2462, 012001 (2023).
[2] F. R. Foronda, F. Lang, J. S. Möller, T. Lancaster, A. T. Boothroyd, F. L. Pratt, S. R. Giblin, D. Prabhakaran and S. J. Blundell, Phys. Rev. Lett. 114, 017602 (2015).
[3] S. J. Blundell et al., in preparation.
| stephen.blundell@physics.ox.ac.uk | |
| Funding Agency | UKRI |
| Did you request an Invitation Letter for a Visitors Visa Application | No |
