In PNAS, "Generic character of charge and spin density waves in superconducting cuprates"

8/18/2022 3:19:45 PM

Significance

The essential physics of the cuprate high-temperature superconductors have been a central focus of condensed-matter physics for more than three decades. Although initially controversial, it is now clear that a ubiquitous tendency toward charge-density-wave (CDW) order is intertwined with the superconductivity. However, this manifests differently in distinct cuprates. On the basis of extensive X-ray and neutron scattering studies of the temperature and doping dependence of the CDW and spin-density-wave (SDW) correlations in one representative cuprate and a comparison with existing studies on other cuprates, we show that there plausibly is a single, preferred CDW order at the microscale, whose manifestation at low temperatures is modified in predictable ways by material-specific details, including its interaction with SDW order.
 
 

Abstract

Charge density waves (CDWs) have been observed in nearly all families of copper-oxide superconductors. But the behavior of these phases across different families has been perplexing. In La-based cuprates, the CDW wavevector is an increasing function of doping, exhibiting the so-called Yamada behavior, while in Y- and Bi-based materials the behavior is the opposite. Here, we report a combined resonant soft X-ray scattering (RSXS) and neutron scattering study of charge and spin density waves in isotopically enriched La1.8x

Eu0.2SrxCuO4 over a range of doping 0.07x0.20. We find that the CDW amplitude is temperature independent and develops well above experimentally accessible temperatures. Further, the CDW wavevector shows a nonmonotonic temperature dependence, exhibiting Yamada behavior at low temperature with a sudden change occurring near the spin ordering temperature. We describe these observations using a Landau–Ginzburg theory for an incommensurate CDW in a metallic system with a finite charge compressibility and spin-CDW coupling. Extrapolating to high temperature, where the CDW amplitude is small and spin order is absent, our analysis predicts a decreasing wavevector with doping, similar to Y and Bi cuprates. Our study suggests that CDW order in all families of cuprates forms by a common mechanism.

This work was published in the Proceedings of the National Academy of Sciences (PNAS) on April 4, 2022.