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Anomalous quantum criticality in the electron-doped cuprates

In the physics of condensed matter, quantum critical phenomena and unconventional superconductivity are two major themes. In electron-doped cuprates, the low critical field (HC2) 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-TCsuperconductivity. Here we present measurements of the low-temperature normal-state thermopower (S) of the electron-doped cuprate superconductor La2−xCexCuO4(LCCO) fromx= 0.11–0.19. We observe quantum critical$S/T$versus$ln(1/T)$behavior over an unexpectedly wide doping rangex= 0.15–0.17 above the QCP (x= 0.14), with a slope that scales monotonically with the superconducting transition temperature (TCwith 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 withTC. Above the superconductivity dome, atx= 0.19, a conventional Fermi-liquid$S∝T$behavior is found for$T≤$40 K.

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Publication Date:
NSF-PAR ID:
10087945
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
116
Issue:
13
Page Range or eLocation-ID:
p. 5991-5994
ISSN:
0027-8424
Publisher:
Proceedings of the National Academy of Sciences
Sponsoring Org:
National Science Foundation
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