Uncovering the secrets of ‘strange metal’ behaviour in a superconducting material

30 Jul 2026 - Rosie de Laune

Using inelastic neutron scattering and computational modelling, a team led by researchers from the University of Bristol have uncovered some key drivers of the strange metal phase of an intriguing quantum material. The origin of high-temperature superconductivity in cuprate materials such as La_2−xSr_xCuO₄ (LSCO) is a puzzle for physicists. However, the behaviour of these materials above their critical temperature, when they are not superconducting, is even more complicated. It’s even defined as ‘strange metal’ behaviour.

Schematic phase diagram of LSCO showing the possible extent of the critical spin fluctuations observed here. The dashed line shows the extent of spin freezing for B = 80 T where superconductivity is fully suppressed and the magenta region for B = 0

Changing the levels of lanthanum and strontium ions in the material introduces holes into the copper oxide layers, due to the different charges of the ions. These holes are the charge carriers that make the material conducting and, under the right conditions, superconducting. If the cuprate is ‘underdoped’, with fewer holes, above the critical temperature there are multiple competing states. However, ‘overdoped’ cuprates with a higher proportion of holes exhibit just one state, which shows strange metal behaviour.

Strange metals get their name from the peculiar behaviour of their electrons. Unlike in ordinary metals, where electrons travel freely with few interactions and little resistance, in strange metals their movement is more restricted. This strange metal phase cannot be explained by conventional theories that treat electrons as independent quantum particles.

In this study, researchers from the University of Bristol and their collaborators from India, the USA and ISIS investigated the strange metal behaviour of LSCO. They focussed on the overdoped region where the strange metal behaviour is clearest.

Using inelastic neutron scattering on LET to measure single crystals of LSCO, they were able to observe the presence of critical spin fluctuations in the strange metal phase and found that they were strongly temperature dependent. Through computational modelling, they could then fit this behaviour to a ‘Griffiths phase’, establishing that low-energy spin excitations and spatial disorder are central to the strange metal behaviour.

The full paper can be found at DOI: 10.1038/s41467-026-71319-w