Abstract
One of the central questions in the cuprate research is the nature of the normal state that develops into high-temperature superconductivity (HTSC). In the normal state of hole-doped cuprates, the existence of a charge density wave (CDW) is expected to shed light on the mechanism of HTSC. With evidence emerging for CDW order in the electron-doped cuprates, the CDW is thought to be a universal phenomenon in high- cuprates. However, the CDW phenomena in electron-doped cuprates are quite different than those in hole-doped cuprates. Here, we study the nature of the putative CDW in an electron-doped cuprate through direct comparisons between as-grown and postannealed (NCCO) single crystals using Cu -edge resonant soft x-ray scattering (RSXS) and angle-resolved photoemission spectroscopy (ARPES). The RSXS result reveals that the nonsuperconducting NCCO shows the same reflections at the wave vector (, 0, ) as the reported superconducting NCCO. This superconductivity-insensitive signal is quite different from the CDW reflection in hole-doped cuprates. Moreover, the ARPES result suggests that the fermiology cannot account for such wave vectors. These results call into question the universality of the CDW phenomenon in the cuprates.
- Received 25 April 2017
DOI:https://doi.org/10.1103/PhysRevX.7.041066
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.
Published by the American Physical Society
Physics Subject Headings (PhySH)
Popular Summary
High-temperature superconductors are materials that conduct electricity with zero resistance at temperatures well above absolute zero. Cuprates, a type of copper-based oxide compound, exhibit this unique behavior, and one of the central focuses in cuprate research is the nature of the so-called “normal state”—the state at temperatures higher than the superconducting temperature. Researchers hope that understanding certain aspects of the normal state will shed light on the physics underlying high-temperature superconductivity. In particular, charge-density-wave (CDW) correlations—the synchronized periodic motion of charge carriers—could provide valuable insight. Given that such correlations have been seen in different types of hole-doped cuprates, it is hoped that CDW phenomena are universal to all high- cuprates. Using experimental studies, we find no evidence that this is the case.
Recent evidence of CDW order in electron-doped cuprates has raised the possibility of universality; however, there are significant differences in the CDW phenomena in electron-doped cuprates and those doped with holes (the absence of an electron). We use resonant soft x-ray scattering and angle-resolved photoemission spectroscopy to explore the electron-doped cuprates, (NCCO). We find that a putative CDW in the NCCO has characteristics that are markedly different from CDWs observed in hole-doped superconducting cuprates.
Our findings indicate that CDWs in the electron-doped cuprates are different from those in hole-doped cuprates.