scholarly journals Enhanced nonlinear interaction of polaritons via excitonic Rydberg states in monolayer WSe2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jie Gu ◽  
Valentin Walther ◽  
Lutz Waldecker ◽  
Daniel Rhodes ◽  
Archana Raja ◽  
...  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Nonlinear Response ◽  
Single Photon ◽  
Optical Nonlinearity ◽  
Optical Nonlinearities ◽  
Quantum Domain ◽  
Exciton Polaritons ◽  
Attractive Candidate ◽  
Excitonic States

AbstractStrong optical nonlinearities play a central role in realizing quantum photonic technologies. Exciton-polaritons, which result from the hybridization of material excitations and cavity photons, are an attractive candidate to realize such nonlinearities. While the interaction between ground state excitons generates a notable optical nonlinearity, the strength of such interactions is generally not sufficient to reach the regime of quantum nonlinear optics. Excited states, however, feature enhanced interactions and therefore hold promise for accessing the quantum domain of single-photon nonlinearities. Here we demonstrate the formation of exciton-polaritons using excited excitonic states in monolayer tungsten diselenide (WSe2) embedded in a microcavity. The realized excited-state polaritons exhibit an enhanced nonlinear response ∼$${g}_{{pol}-{pol}}^{2s} \sim 46.4\pm 13.9\,\mu {eV}\mu {m}^{2}$$gpol−pol2s~46.4±13.9μeVμm2which is ∼4.6 times that for the ground-state exciton. The demonstration of enhanced nonlinear response from excited exciton-polaritons presents the potential of generating strong exciton-polariton interactions, a necessary building block for solid-state quantum photonic technologies.

scholarly journals Exciton-polaron Rydberg states in monolayer MoSe2 and WSe2

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Erfu Liu ◽  
Jeremiah van Baren ◽  
Zhengguang Lu ◽  
Takashi Taniguchi ◽  
Kenji Watanabe ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Excited States ◽  
Ground State ◽  
Transition Metal Dichalcogenides ◽  
Rydberg States ◽  
Energy Shift ◽  
Many Body ◽  
Electron Hole ◽  
Metal Dichalcogenides ◽  
Excitonic States

AbstractExciton polaron is a hypothetical many-body quasiparticle that involves an exciton dressed with a polarized electron-hole cloud in the Fermi sea. It has been evoked to explain the excitonic spectra of charged monolayer transition metal dichalcogenides, but the studies were limited to the ground state. Here we measure the reflection and photoluminescence of monolayer MoSe2 and WSe2 gating devices encapsulated by boron nitride. We observe gate-tunable exciton polarons associated with the 1 s–3 s exciton Rydberg states. The ground and excited exciton polarons exhibit comparable energy redshift (15~30 meV) from their respective bare excitons. The robust excited states contradict the trion picture because the trions are expected to dissociate in the excited states. When the Fermi sea expands, we observe increasingly severe suppression and steep energy shift from low to high exciton-polaron Rydberg states. Their gate-dependent energy shifts go beyond the trion description but match our exciton-polaron theory. Our experiment and theory demonstrate the exciton-polaron nature of both the ground and excited excitonic states in charged monolayer MoSe2 and WSe2.

scholarly journals Prediction of hyperbolic exciton-polaritons in monolayer black phosphorus

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fanjie Wang ◽  
Chong Wang ◽  
Andrey Chaves ◽  
Chaoyu Song ◽  
Guowei Zhang ◽  
...  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Layered Materials ◽  
Black Phosphorus ◽  
Exciton Peak ◽  
High Quality ◽  
Plane Anisotropy ◽  
Exciton Polaritons ◽  
Plasmon Resonances ◽  
Photonic Density

AbstractHyperbolic polaritons exhibit large photonic density of states and can be collimated in certain propagation directions. The majority of hyperbolic polaritons are sustained in man-made metamaterials. However, natural-occurring hyperbolic materials also exist. Particularly, natural in-plane hyperbolic polaritons in layered materials have been demonstrated in MoO3 and WTe2, which are based on phonon and plasmon resonances respectively. Here, by determining the anisotropic optical conductivity (dielectric function) through optical spectroscopy, we predict that monolayer black phosphorus naturally hosts hyperbolic exciton-polaritons due to the pronounced in-plane anisotropy and strong exciton resonances. We simultaneously observe a strong and sharp ground state exciton peak and weaker excited states in high quality monolayer samples in the reflection spectrum, which enables us to determine the exciton binding energy of ~452 meV. Our work provides another appealing platform for the in-plane natural hyperbolic polaritons, which is based on excitons rather than phonons or plasmons.

scholarly journals Fluorescence of molecular composites that consist of nematic liquid crystal and merocyanins

2020 ◽  
Keyword(s):  
Optical Properties ◽  
Liquid Crystal ◽  
Molecular Electronics ◽  
Excited States ◽  
Nematic Liquid Crystal ◽  
Conformational Changes ◽  
Ground State ◽  
Spectral Properties ◽  
Single Photon ◽  
Biological Research

Background: Considered merocyanine molecules have donor D and acceptor A moieties connected by polymer chain. The conjugated donor D and acceptor A parts of merocyanine molecules are planar in the ground state. The D-π-A molecular complexes can change their conformations in an excited state due to cis-trans-conformational transitions. The viscosity of the solvent affects conformational changes, photoluminescence (PL) decay and PL lifetime. Therefore the PL of merocyanine molecules strongly depends on medium in excited and ground states. A nematic liquid crystal was utilized as a solvent for merocyanine molecules since it is characterized by long range order, orientates merocyanine molecules along its axis and is sensitive to external electro-magnetic field. The molecules with conjugated donor D and acceptor A parts are promising for molecular electronics (instruments for recording and processing information), optoelectronics (laser technologies) and biological research (fluorescent probes like prominent thioflavin T), since their PL essentially depends on the nature of the environment. Objectives: The main objective of this paper is to investigate and explain impact of liquid crystal medium on considered molecules. Also influence of molecular conformational changes on their spectral properties is considered. Materials and Methods: Two types of merocyanine molecules M-1 and M-2 were investigated. The spectral properties of molecules in different organic solvents such as acetonitrile, toluene, glycerol, and in 4-pentyl-4′-cyanobiphenyl (5CB) liquid crystal were compared. Stationary and time-resolved emission spectra of molecular merocyanine solutions were used to investigate conformational changes of molecules. To determine a lifetime of molecular excited states, a technique of Time Correlated Single Photon Counting with picosecond resolution in time was used. Results: The results indicate that optical properties strongly depend on conformation of conjugated donor-π-acceptor compounds. A relaxation of dye molecules to the ground state is accompanied by conformational changes. The quantum yield and lifetime of PL increase in more viscous solvents. The liquid crystal made conformational changes of considered molecules in ground and excited states. Conclusions: Analysis of the results serves as a basis for constructing a theory that explains properties of D-π-A molecular compounds under optical excitation. The molecular pairs are formed by merocyanine and liquid crystal molecules. The liquid crystal molecule defines conformation of merocyanine molecule in a pair. Moreover, both types of merocyanine molecules in liquid crystal have the same conformation. This hypothesis explains similarities of optical properties of M-1 and M-2 molecules in liquid crystal.

Excited-State Enhancement of Optical Nonlinearities of Dialkynyl Complexes

1997 ◽  
Vol 06 (01) ◽  
pp. 109-117 ◽  
Author(s):  
Jiang Zhao ◽  
Yougui Wang ◽  
Jinhai Si ◽  
Peixian Ye ◽  
Shijie Li ◽  
...  
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Optical Nonlinearities ◽  
Sample Molecule

Optical nonlinearities of dialkynyl complexes at ground state and excited states have been investigated by DFWM. The nonlinear susceptibilities of the system were enhanced greatly through the population of the excited states. The values of the hyperpolarizabilities of the sample molecule at excited states, γ1111,se and γ1221,se, were determined to be 2.15 × 10-30 esu and 1.17 × 10-30 esu, respectively, while their values at ground state, γ1111,sg and γ1221,sg, were 1.08 × 10-31 esu and 2.30 × 10-32 esu.

Observation of Triplet Doubly Excited States in Single Photon Excitation from Ground State Helium

2001 ◽  
Vol 86 (13) ◽  
pp. 2758-2761 ◽  
Author(s):  
F. Penent ◽  
P. Lablanquie ◽  
R. I. Hall ◽  
M. Žitnik ◽  
K. Bučar ◽  
...  
Keyword(s):  
Excited States ◽  
Ground State ◽  
Single Photon ◽  
Doubly Excited States ◽  
Photon Excitation ◽  
Doubly Excited

Excited-State Dynamics in the RNA Nucleotide Uridine 5’-Monophosphate Investigated by Femtosecond Broadband Transient Absorption Spectroscopy

2019 ◽  
Author(s):  
Matthew M. Brister ◽  
Carlos Crespo-Hernández
Keyword(s):  
Excited State ◽  
Excited States ◽  
Ground State ◽  
Transient Absorption ◽  
Electronic Energy ◽  
Transient Absorption Spectroscopy ◽  
Electronic Relaxation ◽  
Vibrationally Excited ◽  
Excited State Dynamics ◽  
Π State

<p></p><p> Damage to RNA from ultraviolet radiation induce chemical modifications to the nucleobases. Unraveling the excited states involved in these reactions is essential, but investigations aimed at understanding the electronic-energy relaxation pathways of the RNA nucleotide uridine 5’-monophosphate (UMP) have not received enough attention. In this Letter, the excited-state dynamics of UMP is investigated in aqueous solution. Excitation at 267 nm results in a trifurcation event that leads to the simultaneous population of the vibrationally-excited ground state, a longlived <sup>1</sup>n<sub>O</sub>π* state, and a receiver triplet state within 200 fs. The receiver state internally convert to the long-lived <sup>3</sup>ππ* state in an ultrafast time scale. The results elucidate the electronic relaxation pathways and clarify earlier transient absorption experiments performed for uracil derivatives in solution. This mechanistic information is important because long-lived nπ* and ππ* excited states of both singlet and triplet multiplicities are thought to lead to the formation of harmful photoproducts.</p><p></p>

Charge Transfer Between CO22+ and Ar or Ne at Collision Energies 3-10 eV

2003 ◽  
Vol 68 (1) ◽  
pp. 178-188 ◽  
Author(s):  
Libor Mrázek ◽  
Ján Žabka ◽  
Zdeněk Dolejšek ◽  
Zdeněk Herman
Keyword(s):  
Charge Transfer ◽  
Excited States ◽  
Ground State ◽  
Scattering Method ◽  
Translational Energy ◽  
Centre Of Mass ◽  
Energy Distributions ◽  
Zener Model ◽  
Beam Scattering ◽  
Product Ions

The beam scattering method was used to investigate non-dissociative single-electron charge transfer between the molecular dication CO22+ and Ar or Ne at several collision energies between 3-10 eV (centre-of-mass, c.m.). Relative translational energy distributions of the product ions showed that in the reaction with Ar the CO2+ product was mainly formed in reactions of the ground state of the dication, CO22+(X3Σg-), leading to the excited states of the product CO2+(A2Πu) and CO2+(B2Σu+). In the reaction with Ne, the largest probability had the process from the reactant dication excited state CO22+(1Σg+) leading to the product ion ground state CO2+(X2Πg). Less probable were processes between the other excited states of the dication CO22+, (1∆g), (1Σu-), (3∆u), also leading to the product ion ground state CO2+(X2Πg). Using the Landau-Zener model of the reaction window, relative populations of the ground and excited states of the dication CO22+ in the reactant beam were roughly estimated as (X3Σg):(1∆g):(1Σg+):(1Σu-):(3∆u) = 1.0:0.6:0.5:0.25:0.25.

scholarly journals The Microwave Spectrum of 3,4-Dihydro-1,2-Pyran

1985 ◽  
Vol 40 (9) ◽  
pp. 913-919
Author(s):  
Juan Carlos López ◽  
José L. Alonso
Keyword(s):  
Dipole Moment ◽  
Excited States ◽  
Ground State ◽  
Principal Axis ◽  
Microwave Spectrum ◽  
Average Intensity ◽  
Ring Conformation ◽  
Vibrationally Excited ◽  
Rotational Constants ◽  
Displacement Measurements

Abstract The rotational transitions of 3,4-dihydro-1,2-pyran in the ground state and six vibrationally excited states have been assigned. The rotational constants for the ground state (A = 5198.1847(24), B = 4747.8716(24) and C = 2710.9161(24) have been derived by fitting μa, μb and μc-type transitions. The dipole moment was determined from Stark displacement measurements to be 1.400(8) D with its principal axis components |μa| =1.240(2), |μb| = 0.588(10) and |μc| = 0.278(8) D. A model calculation to reproduce the ground state rotational constants indicates that the data are consistent with a twisted ring conformation. The average intensity ratio gives vibrational separations between the ground and excited states of the ring-bending and ring-twisting modes of ~ 178 and ~ 277 cm-1 respectively.

scholarly journals Counting monster potentials

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
Riccardo Conti ◽  
Davide Masoero
Keyword(s):  
Excited States ◽  
Ground State ◽  
Hermite Polynomials ◽  
Large Momentum ◽  
Integer Partitions ◽  
Complex Equilibria ◽  
State Potential

Abstract We study the large momentum limit of the monster potentials of Bazhanov-Lukyanov-Zamolodchikov, which — according to the ODE/IM correspondence — should correspond to excited states of the Quantum KdV model.We prove that the poles of these potentials asymptotically condensate about the complex equilibria of the ground state potential, and we express the leading correction to such asymptotics in terms of the roots of Wronskians of Hermite polynomials.This allows us to associate to each partition of N a unique monster potential with N roots, of which we compute the spectrum. As a consequence, we prove — up to a few mathematical technicalities — that, fixed an integer N , the number of monster potentials with N roots coincides with the number of integer partitions of N , which is the dimension of the level N subspace of the quantum KdV model. In striking accordance with the ODE/IM correspondence.

scholarly journals Optical switching of topological phase in a perovskite polariton lattice

2021 ◽  
Vol 7 (21) ◽  
pp. eabf8049
Author(s):  
Rui Su ◽  
Sanjib Ghosh ◽  
Timothy C. H. Liew ◽  
Qihua Xiong
Keyword(s):  
Optical Switching ◽  
Room Temperature ◽  
Optical Pumping ◽  
Optical Nonlinearity ◽  
Edge States ◽  
Ambient Conditions ◽  
Strong Light ◽  
Exciton Polaritons ◽  
Matter Interaction ◽  
Light Matter Interaction

Strong light-matter interaction enriches topological photonics by dressing light with matter, which provides the possibility to realize active nonlinear topological devices with immunity to defects. Topological exciton polaritons—half-light, half-matter quasiparticles with giant optical nonlinearity—represent a unique platform for active topological photonics. Previous demonstrations of exciton polariton topological insulators demand cryogenic temperatures, and their topological properties are usually fixed. Here, we experimentally demonstrate a room temperature exciton polariton topological insulator in a perovskite zigzag lattice. Polarization serves as a degree of freedom to switch between distinct topological phases, and the topologically nontrivial polariton edge states persist in the presence of onsite energy perturbations, showing strong immunity to disorder. We further demonstrate exciton polariton condensation into the topological edge states under optical pumping. These results provide an ideal platform for realizing active topological polaritonic devices working at ambient conditions, which can find important applications in topological lasers, optical modulation, and switching.

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