CALCULATION OF HUANG-RHYS PARAMETERS AND THEORETICAL ANALYSIS OF INTEGRATED INTENSITIES AND PROFILE OF d-d OPTICAL SPECTRA lN NON-CONDON APPROXIMATION

We develop in this paper the theory of multiphonon radiative transition so that someimportant physical quantities that describe effect s of lattice relaxation in electron transitions,for example, Huang--Rhys parameters, lattice relaxation energies and Stokes shifts, becomecomputable directly. The calculated results of the se physical quantities for alexandrite agreewith experimental data very well. Besides, we deduce expressions of intensity distributionand integrated intensity of a multiphonon sideband in non--Condon approximation. The cal-culated values of integrated intensities are obviously better than the intensity fitting resultsof previous work. From these calculated values we can also acquire a quantitative under-standing of the errors of Condon approximation.

The exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses

This paper studies the exciton-longitudinal-optical-phonon coupling in InGaN/GaN single quantum wells with various cap layer thicknesses by low temperature photoluminescence （PL） measurements. With increasing cap layer thickness, the PL peak energy shifts to lower energy and the coupling strength between the exciton and longitudinal- optical （LO） phonon, described by Huang-Rhys factor, increases remarkably due to an enhancement of the internal electric field. With increasing excitation intensity, the zero-phonon peak shows a blueshift and the Huang-Rhys factor decreases. These results reveal that there is a large built-in electric field in the well layer and the exciton-LO-phonon coupling is strongly affected by the thickness of the cap layer.

Infrared optical absorption of Fr?hlich polarons in metal halide perovskites

The formation of Frohlich polarons in metal halide perovskites,arising from the charge carrier-longitudinal optical(LO)phonon coupling,has been proposed to explain their exceptional properties,but the effective identification of polarons in these materials is still a challenging task.Herein,we theoretically present the infrared optical absorption of Frohlich polarons based on the Huang-Rhys model.We find that multiphonon overtones appear as the energy of the incident photons matches the multiple LO phonons,wherein the average phonon number of a polaron can be directly evaluated by the order of the strongest overtone.These multiphonon structures sensitively depend on the scale of electronic distribution in the ground state and the dimensionality of the perovskite materials,revealing the effective modulation of competing processes between polaron formation and carrier cooling.Moreover,the order of the strongest overtone shifts to higher ones with temperature,providing a potential proof that the carrier mobility is affected by LO phonon scattering.The present model not only suggests a direct way to verify Frohlich polarons but also enriches our understanding of the properties of polarons in metal halide perovskites.

Luminescent properties of thermally activated delayed fluorescence molecule with intramolecular π-π interaction between donor and acceptor

Influence of intramolecular π-π interaction on the luminescent properties of thermally activated delayed fluorescence（TADF） molecule（3, 5-bis（3,6-di-tert-butyl-9 H-carbazol-9-yl）-phenyl）（pyridin-4-yl） methanone（DTCBPY） is theoretically studied by using the density functional theory（DFT） and time-dependent density functional theory（TD-DFT）.Four conformations（named as A, B, C, and D） of the DTCBPY can be found by relax scanning, and the configuration C corresponds to the luminescent molecule detected experimentally. Besides, we calculate the proportion of each conformation by Boltzmann distribution, high configuration ratios（44% and 52%） can be found for C and D. Moreover, C and D are found to exist with an intramolecular π-π interaction between one donor and the acceptor; the intramolecular interaction brings a smaller Huang-Rhys factor and reduced reorganization energy. Our work presents a rational explanation for the experimental results and demonstrates the importance of the intramolecular π-π interaction to the photophysical properties of TADF molecules.

掺杂氟化钠晶体色心的零声子跃迁和光谱烧孔(英文)

在 10～ 77K测量温度范围内 ,从室温伽马辐照着色的掺羟NaF晶体中观察到R2 和N-带零声子线 (ZPLs)。用普通分光光度计的光在 10K下能将N-ZPLs完全漂白。用其更窄带的光在 10K能在此线的吸收光谱上烧出 1个明显的孔。在适当温度下 ,用紫外光照射能将此线的光漂白几乎全部恢复。在不同温度下 ,研究了未掺杂NaF晶体 82 1nmZPL光谱特性随温度的变化关系 ,并估算出对应的Huang Rhys因子约为 2 .4 9。

Simulation of molecular spectroscopy with circuit quantum electrodynamics

Spectroscopy is a crucial laboratory technique for understanding quantum systems through their interactions with the electromagnetic radiation.Particularly,spectroscopy is capable of revealing the physical structure of molecules,leading to the development of the maser—the forerunner of the laser.However,real-world applications of molecular spectroscopy are mostly confined to equilibrium states,due to computational and technological constraints;a potential breakthrough can be achieved by utilizing the emerging technology of quantum simulation.Here we experimentally demonstrate through a toy model,a superconducting quantum simulator capable of generating molecular spectra for both equilibrium and non-equilibrium states,reliably producing the vibronic structure of diatomic molecules.Furthermore,our quantum simulator is applicable not only to molecules with a wide range of electronic-vibronic coupling strength,characterized by the Huang-Rhys parameter,but also to molecular spectra not readily accessible under normal laboratory conditions.These results point to a new direction for predicting and understanding molecular spectroscopy,exploiting the power of quantum simulation.

Temperature dependence of the excitonic spectra of monolayer transition metal dichalcogenides

We theoretically study the temperature dependence of the excitonic spectra of monolayer transitionmetal dichaleogenides using the O＇Donnell equation, Eg（T） = Eg（0） - S〈hω〉[coth（〈hω〉/2kBT- 1）]. We develop a theoretical model for the quantitative estimation of the Huang-Rhys factor S and averagephonon energy （hω） based on exciton coupling with longitudinal optical and acoustic phonons in the Frohlich and deformation potential mechanisms, respectively. We present reasonable explanations for the fitted values of the Huang-Rhys factor and average phonon energy adopted in experiments. Com- parison with experimental results reveals that the temperature dependence of the peak position in the excitonic spectra can be well reproduced by modulating the polarization parameter and deformation potential constant.