- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
[IEEE 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Paris, France (2019.9.1-2019.9.6)] 2019 44th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Identification and Characterization of ‘Killer-Modes’ in Organic Semiconductors with Terahertz Spectroscopy
摘要： Organic semiconductors are promising modern optoelectric materials, with countless potential applications ranging from ?exible displays to photovoltaics. The applicability of these materials is largely driven by their charge carrier mobility, which is strongly in?uenced by low-frequency vibrations. In this work, the speci?c low-frequency vibrations that exhibit strong electron-phonon coupling, deemed ‘killer-modes’, in organic semiconductors are determined using a combination of terahertz time-domain spectroscopy and solid-state density functional theory. The results of this study enable a concerted synthetic effort to rationally design novel materials, utilizing intermolecular forces to stiffen lattice dynamics, to ultimately improve charge carrier mobility.
关键词： electron-phonon coupling,organic semiconductors,charge carrier mobility,solid-state density functional theory,terahertz spectroscopy
更新于2025-09-11 14:15:04
-
Exciton Peierls mechanism and universal many-body gaps in carbon nanotubes
摘要： “Metallic” carbon nanotubes exhibit quasiparticle gaps when isolated from a screening environment. The gap-opening mechanism is expected to be of electronic origin, but the precise nature is debated. In this work, we show that hybrid density functional theory predicts a set of excitonic instabilities capable of opening gaps of the size found in experiment. The excitonic instabilities are coupled to vibrational modes and, in particular, the modes associated with the (cid:2) ? E2g and K ? A(cid:2) 1 Kohn anomalies of graphene, inducing Peierls lattice distortions with a strong electron-phonon coupling. In the larger tubes, the longitudinal optical phonon mode becomes a purely electronic dimerization that is fully symmetry conserving in the zigzag and chiral tubes, but breaks the symmetry in the armchair tubes. The resulting gaps are universal (i.e., independent of chirality) and scale as 1/R with tube radius.
关键词： exciton Peierls mechanism,electron-phonon coupling,many-body gaps,carbon nanotubes,hybrid density functional theory
更新于2025-09-11 14:15:04
-
Cavity quantum-electrodynamical polaritonically enhanced electron-phonon coupling and its influence on superconductivity
摘要： So far, laser control of solids has been mainly discussed in the context of strong classical nonlinear light-matter coupling in a pump-probe framework. Here, we propose a quantum-electrodynamical setting to address the coupling of a low-dimensional quantum material to quantized electromagnetic fields in quantum cavities. Using a prototypical model system describing FeSe/SrTiO3 with electron-phonon long-range forward scattering, we study how the formation of phonon polaritons at the two-dimensional interface of the material modifies effective couplings and superconducting properties in a Migdal-Eliashberg simulation. We find that through highly polarizable dipolar phonons, large cavity-enhanced electron-phonon couplings are possible, but superconductivity is not enhanced for the forward-scattering pairing mechanism due to the interplay between coupling enhancement and mode softening. Our results demonstrate that quantum cavities enable the engineering of fundamental couplings in solids, paving the way for unprecedented control of material properties.
关键词： phonon polaritons,electron-phonon coupling,superconductivity,cavity quantum electrodynamics,quantum materials
更新于2025-09-10 09:29:36
-
Encyclopedia of Spectroscopy and Spectrometry || Optical Spectroscopy of Rare-Earth Ions in the Solid State
摘要： The birth of optical spectroscopy as science can be considered from the time when in 1672 Isaac Newton published his famous paper describing the results of experiments where, using a glass prism, he decomposed a beam of sunlight into its optical spectral components ranging from blue to red. Since that time, scientists and engineers studied a broad range of phenomena associated with the interaction of light with matter, using the fact that light actually contains different spectral components. Within a field of optical spectroscopy, it is hard to underestimate the importance of optical spectroscopy of different optical centers in solid-state materials because of numerous scientific and industrial applications of such optical systems. These applications range from studying fundamental properties of impurity centers in solids, solid-state material properties, up-conversion devices, scintillators, and Faraday rotators to a creation of solid-state lasers.
关键词： rare-earth ions,Fu¨chtbauer–Ladenburg theory,optical spectroscopy,Judd–Ofelt theory,McCumber theory,electron–phonon coupling,Franck–Condon principle,solid state
更新于2025-09-10 09:29:36
-
Effects of Electron-Phonon Coupling on Electronic Properties of Methylammonium Lead Iodide Perovskites
摘要： Temperature can have a dramatic effect on the solar efficiency of methylammonium lead iodide (CH3NH3PbI3) absorbers due to changes in the electronic structure of the system even within the range of stability of a single phase. Herein using first principles density functional theory, we investigate the electron band structure of the tetragonal and orthorhombic phases of CH3NH3PbI3 as a function of temperature. The electron-phonon interactions are computed to all orders using a Monte Carlo approach, which is needed considering that the second-order Allen-Heine-Cardona theory in electron-phonon coupling is not adequate. Our results show that the band gap increases with temperature in excellent agreement with experimental results. We verified that anharmonic effects are only important near the tetragonal-cubic phase transition temperature. We also found that temperature has a significant effect on the effective masses and Rashba coupling. At room temperature, electron–phonon coupling is found to enhance the band effective mass by a factor of two, and to diminish the Rashba coupling by the same factor compared to T=0 K values. Our results underscore the significant impact of electron-phonon coupling on electronic properties of the hybrid perovskites.
关键词： Energy Conversion and Storage,Methylammonium Lead Iodide Perovskites,Plasmonics and Optoelectronics,Electron-Phonon Coupling,Electronic Properties
更新于2025-09-10 09:29:36
-
Effect of B2O3 Content on Eu3+?Surrounding in The System SrO?x.B2O3 Containing Eu3+ Ions Prepared by Combustion Method
摘要： The change of Eu3+? surrounding in the system SrO?x.B2O3 with various x values (x = 0.33, 0.5, 1) synthesized by combustion method was investigated via photoluminescence (PL) spectra and phonon sideband (PSB) spectra. From the analysis of PSB spectra, it is reasonable to suggest that when increasing B2O3 content the electron?phonon coupling strength increases due to the increase in the number of B?O? non?bridging bond. By using Judd?Ofelt (JO) theory for PL spectra of Eu3+ ion, the ?2 intensity parameter was calculated and it also shows the asymmetry of Eu3+? surrounding increase corresponding to the B2O3 content.
关键词： Eu3+,Judd?Ofelt theory,Combustion method,electron-phonon coupling,B2O3,phonon sideband
更新于2025-09-09 09:28:46
-
Decoupling Carrier Concentration and Electron-Phonon Coupling in Oxide Heterostructures Observed with Resonant Inelastic X-Ray Scattering
摘要： We report the observation of multiple phonon satellite features in ultrathin superlattices of the form nSrIrO3=mSrTiO3 using resonant inelastic x-ray scattering (RIXS). As the values of n and m vary, the energy loss spectra show a systematic evolution in the relative intensity of the phonon satellites. Using a closed-form solution for the RIXS cross section, we extract the variation in the electron-phonon coupling strength as a function of n and m. Combined with the negligible carrier doping into the SrTiO3 layers, these results indicate that the tuning of the electron-phonon coupling can be effectively decoupled from doping. This work both showcases a feasible method to extract the electron-phonon coupling in superlattices and unveils a potential route for tuning this coupling, which is often associated with superconductivity in SrTiO3-based systems.
关键词： superlattices,electron-phonon coupling,SrTiO3,SrIrO3,resonant inelastic x-ray scattering
更新于2025-09-09 09:28:46
-
Coherent optical and acoustic phonons generated at lattice-matched GaP/Si(001) heterointerfaces
摘要： Thin GaP films can be grown on an exact Si(001) substrate with nearly perfect lattice match. We perform all-optical pump-probe measurements to investigate the ultrafast electron-phonon coupling at the buried interface of GaP/Si. Above-bandgap excitation with a femtosecond laser pulse can induce coherent longitudinal optical (LO) phonons both in the GaP overlayer and in the Si substrate. The coupling of the GaP LO phonons with photoexcited plasma is reduced significantly with decreasing the GaP layer thickness from 56 to 16 nm due to the quasi-two-dimensional confinement of the plasma. The same laser pulse can also generate coherent longitudinal acoustic (LA) phonons in the form of a strain pulse. The strain pulses induce not only a periodic modulation in the optical reflectivity as they propagate in the semiconductors, but also a sharp spike when it arrives at the GaP layer boundaries. The acoustic pulse induced at the GaP/Si interface is remarkably stronger than that at the Si surface, suggesting a possible application of the GaP/Si heterostructure as an opto-acoustic transducer. The amplitude and the phase of the reflectivity modulation varies with the GaP layer thickness, which can be understood in terms of the interference caused by the multiple acoustic pulses generated at the top surface and at the buried interface.
关键词： opto-acoustic transducer,GaP/Si heterointerfaces,coherent acoustic phonons,ultrafast electron-phonon coupling,coherent optical phonons
更新于2025-09-09 09:28:46
-
Demonstration of resonant inelastic x-ray scattering as a probe of exciton-phonon coupling
摘要： Resonant inelastic x-ray scattering (RIXS) is a promising technique for obtaining electron-phonon coupling constants. However, the ability to extract these coupling constants throughout the Brillouin zone for crystalline materials remains limited. To address this need, we developed a Green’s function formalism to capture electron-phonon contributions to core-level spectroscopies without explicitly solving the full vibronic problem. Our approach is based on the cumulant expansion of the Green’s function combined with many-body theory calculated vibrational coupling constants. The methodology is applied to x-ray photoemission spectroscopy, x-ray absorption spectroscopy (XAS), and RIXS. In the case of the XAS and RIXS, we use a two-particle exciton Green’s function, which accounts implicitly for particle-hole interference effects that have previously proved difficult. To demonstrate the methodology and gain a deeper understanding of the experimental technique, we apply our formalism to small molecules, for which unambiguous experimental data exist. This comparison reveals that the vibronic coupling constant probed by RIXS is in fact related to exciton-phonon coupling rather than electron-phonon coupling, challenging the conventional interpretation of the experiment.
关键词： electron-phonon coupling,Green’s function formalism,exciton-phonon coupling,Resonant inelastic x-ray scattering,vibronic coupling
更新于2025-09-04 15:30:14
-
Unusual polarization and temperature-dependent Raman response in Weyl semimetal NbIrTe4
摘要： We carry out a systematic study of polarized- and temperature-dependent Raman scattering of layered Weyl semimetal NbIrTe4 on the (002) crystal surface, under parallel and perpendicular polarization Raman spectroscopy geometry in back scattering way, the angle-dependent Raman peaks intensity is recorded by rotating the single crystal from 0° to 360°, in combination with group theory analysis, all the prominent Raman peaks are assigned to A1 and B1 vibrational modes, moreover, we show that the angular dependence of Raman peak intensity of A1 mode is rather unusual and can be explained by complex values for Raman tensor elements, which is traced back to electron-phonon interaction in this material. Meanwhile, lattice anharmonic vibrational behavior is studied by investigating the temperature-dependent Raman scattering spectra, it is observed that all the Raman peaks show linear sti?ening behavior as the temperature decreased from 293 K to 83 K, the temperature coe?cients of four prominent Raman peaks suggest the anharmonicity of the lattice in layered NbIrTe4 crystal.
关键词： Lattice anharmonicity,Electron-phonon coupling,Vibrational modes,Polarized Raman scattering
更新于2025-09-04 15:30:14