Raman scattering with strongly coupled vibron-polaritons

Strong coupling between cavity photons and molecular vibrations can lead to the formation of vibron-polaritons. In a recent experiment with PVAc molecules in a metal-metal microcavity [A.Shalabney et al., Ang.Chem.Int.Ed. 54 7971 (2015)], such a coupling was observed to enhance the Raman scattering probability by several orders of magnitude. Inspired by this, we theoretically analyze the effect of strong photon-vibron coupling on the Raman scattering amplitude of organic molecules. This problem has recently been addressed in [J.del Pino, J.Feist and F.J.Garcia-Vidal; J.Phys.Chem.C 119 29132 (2015)] using exact numerics for a small number of molecules. In this paper we derive compact analytic results for any number of molecules, also including the ultra-strong coupling regime. Our calculations predict a division of the Raman signal into upper and lower polariton modes,with some enhancement to the lower polariton Raman amplitude due to the mode softening under strong coupling.PostprintPeer reviewe

Strong matter-light coupling with organic molecules and inorganic semiconductors

This dissertation studies the effects of strong matter-light coupling on properties of organic molecules and inorganic semiconductors. The interplay of complex intramolecular dynamics and strong coupling of a photon to molecular transitions results in new physics having no counterparts in other systems. In contrast, low-energy optically active excitations of semiconductors (excitons) usually do not feature such complexity. However, the combination of strong electronic correlations and strong matter-light coupling leads to new physics. Firstly, the effect of strong coupling between molecular vibrations and infrared photons on Raman scattering (RS) is considered. This is motivated by the experiment of Ref. [1] showing up to 10³ enhancement of RS signal under strong coupling. While the exact analytical results of this dissertation predict around 100% enhancement of total RS signal, they cannot explain orders of magnitude enhancement, leaving the question open for further studies. Next, the effects of strong coupling of an optical photon and a molecular electronic transition on molecular lasing properties are discussed. Starting from a microscopic description of a driven-dissipative system, an exact (in the thermodynamic limit) mean-field solution is developed. It allows to uncover the mechanism of molecular lasing in the weak and strong coupling regime and to obtain a non-equilibrium lasing phase diagram. Finally, a semiconductor with different densities of electrons and holes, strongly coupled to a microcavity photon, is studied. While finite electron-hole density imbalance is detrimental for excitonic condensation, it may still lead to a condensed state of excitons with finite centre of mass momentum coexisting with unpaired electrons. On the other hand, due to its low mass, a photon favours zero center of mass momentum condensation. The variational mean-field calculations reveal that the interplay of these effects leads to a variety of novel states with coexisting polariton condensate and unpaired electrons."This work was supported by the Engineering and Physical Sciences Research Council, the Scottish Doctoral Training Centre in Condensed Matter Physics (grant number EP/L015110/1)." -- Fundin

Electrical Control of Two-Dimensional Electron-Hole Fluids in the Quantum Hall Regime

We study the influence of quantizing perpendicular magnetic fields on the ground state of a bilayer with electron and hole fluids separated by an opaque tunnel barrier. In the absence of a field, the ground state at low carrier densities is a condensate of s-wave excitons that has spontaneous interlayer phase coherence. We find that a series of phase transitions emerge at strong perpendicular fields between condensed states and incompressible incoherent states with full electron and hole Landau levels. When the electron and hole densities are unequal, condensation can occur in higher angular momentum electron-hole pair states and, at weak fields, break rotational symmetry. We explain how this physics is expressed in dual-gate phase diagrams, and predict transport and capacitively-probed thermodynamic signatures that distinguish different states

Organic polariton lasing and the weak- to strong-coupling crossover

Following experimental realizations of room temperature polariton lasing with organic molecules, we present a microscopic model that allows us to explore the crossover from weak to strong matter-light coupling. We consider a non-equilibrium Dicke-Holstein model, including both strong coupling to vibrational modes and strong matter-light coupling, providing the phase diagram of this model in the thermodynamic limit. We discuss the mechanism of polariton lasing, uncovering a process of self-tuning, and identify the relation and distinction between regular dye lasers and organic polariton lasers.PostprintPeer reviewe

Crescent states in charge-imbalanced polariton condensates

Funding: AS acknowledges support from the EPSRC CM-CDT (EP/L015110/1) and a travel award from the Scottish Universities Physics Alliance. AS, AHM and JK acknowledge financial support from a Royal Society International Exchange Award, IES\R2\170213. FMM acknowledges financial support from the Spanish Ministry of Science and Innovation through the project No. MAT2017-83772-R and the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M). JK acknowledges financial support from EPSRC program “Hybrid Polaritonics” (EP/M025330/1). AHM acknowledges support from Army Research Office (ARO) Grant # W911NF-17-1-0312 (MURI). This work was performed in part at Aspen Center for Physics, which is supported by National Science Foundation grant PHY-1607611 and partially supported by a grant from the Simons Foundation.We study two-dimensional charge-imbalanced electron-hole systems embedded in an optical microcavity. We find that strong coupling to photons favors states with pairing at zero or small center of mass momentum, leading to a condensed state with spontaneously broken time-reversal and rotational symmetry, and unpaired carriers that occupy an anisotropic crescent-shaped sliver of momentum space. The crescent state is favoured at moderate charge imbalance, while a Fulde–Ferrel–Larkin–Ovchinnikov-like state — with pairing at large center of mass momentum — occurs instead at strong imbalance. The crescent state stability results from long-range Coulomb interactions in combination with extremely long-range photon-mediated interactions.Publisher PDFPeer reviewe

Multimode organic polariton lasing

Funding: KBA and JK acknowledge financial support from EPSRC program “Hybrid Polaritonics” (EP/M025330/1). AJM and PT acknowledge support by the Academy of Finland under project numbers 303351, 307419, 327293, 318987 (QuantERA project RouTe) and 318937 (PROFI), and by Centre for Quantum Engineering (CQE) at Aalto University. AJM acknowledges financial support by the Jenny and Antti Wihuri Foundation. AS acknowledges support from the EPSRC CM-CDT (EP/L015110/1).We present a beyond-mean-field approach to predict the nature of organic polariton lasing, accounting for all relevant photon modes in a planar microcavity. Starting from a microscopic picture, we show how lasing can switch between polaritonic states resonant with the maximal gain, and those at the bottom of the polariton dispersion. We show how the population of nonlasing modes can be found, and by using two-time correlations, we show how the photoluminescence spectrum (of both lasing and nonlasing modes) evolves with pumping and coupling strength, confirming recent experimental work on the origin of blueshift for polariton lasing.Publisher PDFPeer reviewe

Organic polariton lasing and the weak- to strong-coupling crossover

Following experimental realizations of room temperature polariton lasing with organic molecules, we present a microscopic model that allows us to explore the crossover from weak to strong matter-light coupling. We consider a non-equilibrium Dicke-Holstein model, including both strong coupling to vibrational modes and strong matter-light coupling, providing the phase diagram of this model in the thermodynamic limit. We discuss the mechanism of polariton lasing, uncovering a process of self-tuning, and identify the relation and distinction between regular dye lasers and organic polariton lasers

Crescent states in charge-imbalanced polariton condensates

We study two-dimensional charge-imbalanced electron-hole systems embedded in an optical microcavity. We find that strong coupling to photons favors states with pairing at zero or small center of mass momentum, leading to a condensed state with spontaneously broken time-reversal and rotational symmetry, and unpaired carriers that occupy an anisotropic crescent-shaped sliver of momentum space. The crescent state is favoured at moderate charge imbalance, while a Fulde–Ferrel–Larkin–Ovchinnikov-like state — with pairing at large center of mass momentum — occurs instead at strong imbalance. The crescent state stability results from long-range Coulomb interactions in combination with extremely long-range photon-mediated interactions

Multimode organic polariton lasing

We present a beyond-mean-field approach to predict the nature of organic polariton lasing, accounting for all relevant photon modes in a planar microcavity. Starting from a microscopic picture, we show how lasing can switch between polaritonic states resonant with the maximal gain, and those at the bottom of the polariton dispersion. We show how the population of nonlasing modes can be found, and by using two-time correlations, we show how the photoluminescence spectrum (of both lasing and nonlasing modes) evolves with pumping and coupling strength, confirming recent experimental work on the origin of blueshift for polariton lasing

Data Underpinning - Raman scattering with strongly coupled vibron-polaritons

The attached data files underpin the publication “Raman scattering with strongly coupled vibron-polaritons”. The following file types and formats are included: - cavity-raman-figures: .nb (this file contains all the figures and graphs oblained in this work; can be opened with Mathematica 10