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Berlin 2015 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 36: SYHM Higgs Modes in Condensed Matter and Quantum Gases

DY 36.4: Hauptvortrag

Mittwoch, 18. März 2015, 16:45–17:15, H 0105

Amplitude Higgs Mode in 2H-NbSe2 Superconductor — •Marie-Aude Méasson1, Romain Grasset1, Yann Gallais1, Max Cazayous1, Alain Sacuto1, Pierre Rodière2, and Laurent Cario31LMPQ, Universite Paris 7-CNRS, France — 2Institut Neel, Grenoble, France — 3IMN, Universite de Nantes, France

When a spontaneous breaking of a continuous symmetry takes place, as happens during a superconducting transition, collective excitations such as the amplitude Higgs mode of the order parameter emerge. The existence of such Higgs mode was proposed in the charge density wave (CDW) superconductor (SC) 2H-NbSe2, after the first experimental observation by Raman scattering. The Higgs mode could be unraveled via its coupling to the coexisting charge density wave mode. We will address here the questions of the nature of this mode as well as the mechanism of its observability.

We report experimental evidences for the Higgs mode scenario in 2H-NbSe2 using Raman scattering. By comparing 2H-NbSe2 and its iso-structural partner 2H-NbS2 which shows superconductivity but lacks the charge density wave order and by destroying the coexisting CDW order under high pressure in 2H-NbSe2, we demonstrate that the superconducting mode owes its spectral weight to the presence of the coexisting charge density wave order. In addition a full spectral weight transfer between both modes operates in 2H-NbSe2 upon entering the superconducting phase. All these observations are consistent with a superconducting Higgs mode. Intriguing symmetry dependent results under pressure will be discussed.

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