Order Parameter Fluctuations at a Buried Quantum Critical Point

TitleOrder Parameter Fluctuations at a Buried Quantum Critical Point
Publication TypeJournal Article
Year of Publication2012
AuthorsFeng, Y, Wang, J, Jaramillo, R, Van Wezel, J, Haravifard, S, Srajer, G, Liu, Y, Xu, Z-A, Littlewood, PB, Rosenbaum, TF
JournalProceedings of the National Academy of Sciences
Pagination7224 - 7229
Date Published2012/05/08/
ISBN Number0027-8424, 1091-6490
KeywordsCharge Density Waves, Pressure, Quantum Criticality, Quantum Phase Transitions, X-Ray Scattering

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.

Short TitlePNAS