Superconductors and Charge Density Waves

Scientists reveal the source of charge density waves in superconductors

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(a)-(c) RIXS spectra of La2-xSrxCuO4 for (a) x=0.12, (b) x=0.21, (c) c=0.25. Red points are a fit to the phonon and the enhanced intensity around zero energy and H=-0.23. (d) Shows the atomic displacements involved in the phonon studied. Image credit: J. Q. Lin et. al. Phys. Rev. Lett. 124, 207005

The Science           

Scientists showed that charge density waves form from electronic effects, not lattice effects, in cuprates, a special class of superconductors.

The Impact

Understanding the origin of charge density waves is a central piece of the puzzle of high-temperature superconductivity, since the two have been shown to be closely interconnected. Superconductors are materials that can conduct electricity with almost zero resistance and, if realized at room temperature, have many applications.


Superconductors are a class of materials that can conduct electricity with almost zero resistance and hold the promise to revolutionize modern life as we know it; however, they must be chilled to nearly absolute zero, the coldest temperature possible.  Researchers are searching for materials that superconduct at higher temperature— a class of materials called high-temperature superconductors— and are zeroing in on one particular group of materials, called cuprates, that show promise for operating at higher temperatures. Scientists have studied these materials for over 30 years but cannot fully explain how they work—a necessary step towards engineering the “holy grail” of cuprates—a versatile, robust material that can superconduct at room temperature and ambient pressure.

In this work, a team of researchers discovered some new information about the electronic behavior of a particular cuprate using an x-ray technique that has not been widely used to study them. They investigated the cuprate at the Soft Inelastic X-Ray (SIX) beamline at the National Synchrotron Light Source II (NSLS-II), a U.S. Department of Energy (DOE) Office of Science User Facility located at DOE’s Brookhaven National Laboratory. The team measured a specific arrangement of electric charge that arises in cuprates—an ordered pattern of electrons known as a charge-density wave (CDW). The SIX beamline offers ultrahigh energy resolution for investigating excitations of both valence electrons and phonons—the collective vibrations of the atomic lattice. The team looked for a dependence of the measured spectra to the doping level with the various samples of the materials but found that the spectra are not related to excitations.

After careful analysis of the data, the team concluded that CDWs are driven by “strong correlations”—a term used to describe not-well-defined electronic behaviors in materials—between electrons, adding support to the idea that the response to the measurement in the cuprates is driven by how the CDW modifies the crystal lattice and how those modifications invoke more complex interactions.

This work offers a new piece in the puzzle that is the physics of the cuprate superconductors.

Download the research summary slide

Related Links

Feature Story:  “A New Approach for Studying Electric Charge Arrangements in a Superconductor


X. Lui
ShanghaiTech University

M. Dean
Brookhaven National Laboratory


J. Q. Lin, H. Miao, D. G. Mazzone, G. D. Gu, A. Nag, A. C. Walters, M. García-Fernández, A. Barbour, J. Pelliciari, I. Jarrige, M. Oda, K. Kurosawa, N. Momono, Ke-Jin Zhou, V. Bisogni, X. Liu, and M. P. M. Dean. Strongly Correlated Charge Density Wave in La2−xSrxCuO4 Evidenced by Doping-Dependent Phonon Anomaly. Physical Review Letters 124, 207005. DOI: 10.1103/PhysRevLett.124.207005


This material is based upon work supported by the U.S. Department of Energy, Office of Basic Energy Sciences. Work at Brookhaven National Laboratory was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DESC0012704. X-ray research was supported by Field Work Proposal No. 23357. Data interpretation at ShanghaiTech University were supported by the ShanghaiTech University startup fund, MOST of China under Grant No. 2016YFA0401000, NSFC under Grant No. 11934017 and the Chinese Academy of Sciences under Grant No. 112111KYSB20170059. The research by V. B. was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Early Career Award Program. This research used resources at the Soft Inelastic X-Ray (SIX) beamline of the National Synchrotron Light Source II, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The Diamond Light Source is acknowledged for time on Beamline I21 under Proposal 22261.

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