Physics

Singular spin fluctuations in the strange-metal phase of La2-xSrxCuO4

B. Costarella, L. Soriano, et al.

Featured May 25, 2026

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Simply

Using a special magnetic measurement technique in strong fields, scientists found that the tiny magnetic wiggles inside a "strange metal" material get super intense as it gets colder, hinting at a hidden quantum critical point and explaining its weird electrical behavior.

In depth

The paper provides direct evidence that low-energy spin fluctuations in the strange-metal phase of overdoped La

_{2 - x}

_{x}

CuO

_{4}

exhibit a singular, divergent behavior as temperature approaches zero. This finding, enabled by using high magnetic fields to suppress superconductivity and employing $^{139}$La NMR (a more robust probe than

^{63}

Cu NMR), suggests these fluctuations are a plausible microscopic origin for the linear-in-temperature resistivity observed in strange metals, even in spatially inhomogeneous samples.

Key Takeaways

1
The low-energy dynamical spin susceptibility $χ^{''} (q, ω)$ in overdoped La $_{2 - x}$ Sr $_{x}$ CuO $_{4}$ shows singular, divergent behavior at low temperatures, suggesting quantum-critical fluctuations.
2
This singular behavior was uncovered by employing high magnetic fields to suppress superconductivity and utilizing $^{139}$La NMR, which is a more robust probe than $^{63}$ Cu NMR for low-temperature spin dynamics in this regime.
3
The observed spin dynamics are spatially inhomogeneous, with a distribution of spin-lattice relaxation rates, suggesting that nanoscale electronic inhomogeneity may underlie the apparent paradox of quantum-critical-like behavior beyond the known spin-stripe critical doping.

Conceptual Flow

HIGH LEVEL

Methodology: Probing Hidden Spin Dynamics

To see tiny magnetic wiggles in a special material, scientists used a strong magnet to turn off its "super-cold" behavior and then listened with a special atomic radio.

Special Material

Strong Magnet

Turn Off Super-Cold State

Listen to Tiny Wiggles

Results: Singular Magnetic Wiggles Found

They found that these tiny magnetic wiggles got much stronger as it got colder, showing the material is on the edge of a big change, which helps explain its strange electricity.

Tiny Wiggles Data

Analyze Cold Behavior

Wiggles Get Stronger

Explains Strange Electricity