Cavity engineering of Hubbard U via phonon polaritons. (1st April 2022)

• Record Type: Journal Article
• Authors: Le Dé, Brieuc; Eckhardt, Christian J; Kennes, Dante M; Sentef, Michael A
• Is Part Of: JPhys materials. Volume 5:Number 2(2022)
• Publication Date: 2022-04-01
• Subjects: polaritons -- quantum optics -- strongly correlated materials -- quantum materials -- Floquet engineering; Solid state physics -- Periodicals; Materials science -- Periodicals; 530.41
• DOI: 10.1088/2515-7639/ac618e
• Languages: English
• ISSNs: 2515-7639

Abstract

Abstract: Pump-probe experiments have suggested the possibility to control electronic correlations by driving infrared-active (IR-active) phonons with resonant midinfrared laser pulses. In this work we study two possible microscopic nonlinear electron-phonon interactions behind these observations, namely coupling of the squared lattice displacement either to the electronic density or to the double occupancy. We investigate whether photon-phonon coupling to quantized light in an optical cavity enables similar control over electronic correlations. We first show that inside a dark cavity electronic interactions increase, ruling out the possibility that T c in superconductors can be enhanced via effectively decreased electron-electron repulsion through nonlinear electron-phonon coupling in a cavity. We further find that upon driving the cavity, electronic interactions decrease. Two different regimes emerge: (i) a strong coupling regime where the phonons show a delayed response at a time proportional to the inverse coupling strength, and (ii) an ultra-strong coupling regime where the response is immediate when driving the phonon polaritons resonantly. We further identify a distinctive feature in the electronic spectral function when electrons couple to phonon polaritons involving an IR-active phonon mode, namely the splitting of the shake-off band into three bands. This could potentially be observed by angle-resolved photoemission spectroscopy.