Order parameter fluctuations at a buried quantum critical point

Yejun Feng, Jiyang Wang, R. Jaramillo, Jasper Van Wezel, S. Haravifard, G. Srajer, Y. Liu, Z. A. Xu, P. B. Littlewood, T. F. Rosenbaum

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Abstract

Quantum criticality is a central concept in condensed matter physics, but the direct observation of quantum critical fluctuations has remained elusive. Here we present an X-ray diffraction study of the charge density wave (CDW) in 2H-NbSe2 at high pressure and low temperature, where we observe a broad regime of order parameter fluctuations that are controlled by proximity to a quantum critical point. X-rays can track the CDW despite the fact that the quantum critical regime is shrouded inside a superconducting phase; and in contrast to transport probes, allow direct measurement of the critical fluctuations of the charge order. Concurrent measurements of the crystal lattice point to a critical transition that is continuous in nature. Our results confirm the long-standing expectations of enhanced quantum fluctuations in low-dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.

Original languageEnglish (US)
Pages (from-to)7224-7229
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume109
Issue number19
DOIs
StatePublished - May 8 2012

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Feng, Y., Wang, J., Jaramillo, R., Van Wezel, J., Haravifard, S., Srajer, G., Liu, Y., Xu, Z. A., Littlewood, P. B., & Rosenbaum, T. F. (2012). Order parameter fluctuations at a buried quantum critical point. Proceedings of the National Academy of Sciences of the United States of America, 109(19), 7224-7229. https://doi.org/10.1073/pnas.1202434109