Order parameter fluctuations at a buried quantum critical point |
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Authors: | Feng Yejun Wang Jiyang Jaramillo R van Wezel Jasper Haravifard S Srajer G Liu Y Xu Z-A Littlewood P B Rosenbaum T F |
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Institution: | The Advanced Photon Source, Argonne National Laboratory, Argonne, IL 60439, USA. |
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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-NbSe(2) 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. |
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Keywords: | incommensurate electronic state transition metal dichalcogenides diffraction line shapes diamond anvil cell |
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