Anomalous quantum criticality in the electron-doped cuprates.
basic_science · Level V
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- Record sourced from PubMed, PMID 30862739.
- Also identified by DOI 10.1073/pnas.1817653116 and PMC identifier 6442589.
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Abstract
In the physics of condensed matter, quantum critical phenomena and unconventional superconductivity are two major themes. In electron-doped cuprates, the low critical field (H<sub>C2</sub>) allows one to study the putative quantum critical point (QCP) at low temperature and to understand its connection to the long-standing problem of the origin of the high-<i>T<sub>C</sub></i> superconductivity. Here we present measurements of the low-temperature normal-state thermopower (<i>S</i>) of the electron-doped cuprate superconductor La<sub>2-<i>x</i></sub> Ce <sub><i>x</i></sub> CuO<sub>4</sub> (LCCO) from <i>x</i> = 0.11-0.19. We observe quantum critical [Formula: see text] versus [Formula: see text] behavior over an unexpectedly wide doping range <i>x</i> = 0.15-0.17 above the QCP (<i>x</i> = 0.14), with a slope that scales monotonically with the superconducting transition temperature (<i>T<sub>C</sub></i> with H = 0). The presence of quantum criticality over a wide doping range provides a window on the criticality. The thermopower behavior also suggests that the critical fluctuations are linked with <i>T<sub>C</sub></i> Above the superconductivity dome, at <i>x</i> = 0.19, a conventional Fermi-liquid [Formula: see text] behavior is found for [Formula: see text] 40 K.