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

Research output: Contribution to journalArticle (Academic Journal)peer-review

47 Citations (Scopus)


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 longstanding expectations of enhanced quantum fluctuations in low dimensional systems, and may help to constrain theories of the quantum critical Fermi surface.
Original languageEnglish
Pages (from-to)7224-7229
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number19
Publication statusPublished - 8 May 2012


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