Collective modes are witnesses of their underlying quantum order, such as superconductivity. Experimental observations of the collective amplitude mode of the superconducting state, named the Higgs mode due to its analogy with the high energy particle, are still scarce and controversial, despite being a fundamental outcome of the theory of superconductivity. Besides, many crucial questions remain open, like the mechanism of its observability, its mere existence in two-dimensional or unconventional superconductors, to name a few. Similarly to the Higgs boson, its detection remains a challenge for physicists.
I identified a potential mechanism of observability making the Higgs mode detectable by Raman spectroscopy, based on the interplay between an adjacent quantum order and superconductivity. I propose here to unravel and investigate the full capability of this mechanism, and to develop a new framework for the quest of the Higgs mode. A first objective is to unveil the key ingredients of this observability by diversifying the type of adjacent order. A second objective is to explore the Higgs mode observability and nature in unconventional situations; in exotic superconductors and in the proximity of quantum criticality. As third objective, I change the dimensionality of the systems and investigate the Higgs mode stability in two-dimensional superconductors. I propose to monitor the detectability and nature of the Higgs mode in this careful selection of situations using advanced Raman spectroscopic techniques under extreme conditions at very low temperature, under lattice-density tuning or high magnetic field.
This project will establish definitive examples of the observation and mechanism of observability of the Higgs mode in superconductors, while developing its phenomenology to address major problems at the frontier of quantum materials research, with impact beyond mere superconductivity and even condensed matter.
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