Sum-frequency generation (SFG) spectroscopy provides a versatile method for the investigation of non-centrosymmetric media and interfaces. Here, using tunable picosecond infrared (IR) pulses from a free-electron laser, the nonlinear optical response of 4H-SiC, a common polytype of silicon carbide, has been probed in the frequency- and time-domain by infrared-visible vibrational SFG spectroscopy. In the SFG spectra we observe a sharp resonance near the longitudinal optical phonon frequency, arising from linear optical effects due the epsilon-near-zero regime of the IR permittivity. In the time domain, the build-up of the SFG intensity is linked to the free-induction decay of the induced coherent IR polarization. When approaching the frequency of the phonon resonance, a slower polarization dephasing is observed as compared to off-resonant IR excitation. Thus, by introducing a temporal delay between the IR and the visible up-conversion pulse we are able to demonstrate spectral narrowing of the phonon SFG resonance, as corroborated by model calculations.
Temperature-driven narrowing of the insulating gap as a precursor of the insulator-to-metal transition: Implications for the electronic structure of solids
Time-domain extreme ultraviolet diffuse scattering spectroscopy of nanoscale surface phonons
Elettra Sincrotrone Trieste（的里雅斯特同步辐射中心）；Massachusetts Institute of Technology（麻省理工学院）；Ca’ Foscari University of Venice（威尼斯卡福斯卡里大学）；Max Born Institute（马克斯·玻恩研究所）；University of Bern（伯尔尼大学）；Università degli Studi di Trieste（的里雅斯特大学）；University of Erlangen-Nürnberg（埃尔朗根-纽伦堡大学）；University of Siegen（锡根大学）；Synchrotron SOLEIL（SOLEIL同步辐射中心）；Lawrence Berkeley National Lab（劳伦斯伯克利国家实验室）；Stanford Institute for Materials and Energy Sciences, SLAC National Accelerator Laboratory（斯坦福材料与能源科学研究所，SLAC国家加速器实验室）；Stanford PULSE Institute, SLAC National Accelerator Laboratory（斯坦福PULSE研究所，SLAC国家加速器实验室）
Probing the multi spin-phonon coupling and local B-site disorder in Pr2CoFeO6 by Raman spectroscopy and correlation with its electronic structure by X-ray photoemission spectroscopy
Angle-Resolved Cryogenic Brillouin-Mandelstam Spectroscopy of Surface and Bulk Acoustic Phonons in Diamond
University of California, Los Angeles（加州大学洛杉矶分校）；California NanoSystems Institute, University of California, Los Angeles（加州纳米系统研究所）；Auburn University（奥本大学）；Center for Quantum Science and Engineering, University of California, Los Angeles（量子科学与工程中心）
Time-Resolved Photoemission Spectroscopy of Quantum Materials Using High Harmonic Generation: Probing Electron-Phonon Interactions and Non-Equilibrium Dynamics
Institute for Solid State Physics, The University of Tokyo（东京大学固体物理研究所）；Trans-scale Quantum Science Institute, The University of Tokyo（东京大学跨尺度量子科学研究所）；Material Innovation Research Center, The University of Tokyo（东京大学材料创新中心）
Thermal conductivity of GeTe/Sb$_{2}$Te$_{3}$ superlattices measured by coherent phonon spectroscopy
利用飞秒相干声子谱研究了GeTe/Sb $_{2}$ Te $_{3}$超晶格的晶格热导率。在非晶和晶态GeTe/$_{2}$ SL薄膜中获得的时间分辨瞬态反射率在太赫兹（THz）频率下具有皮秒退相时间的相干$A_{1}$光学模式。基于德拜理论，我们计算了晶格热导率，包括晶界散射、点缺陷散射、umklapp过程和声子共振散射。结果表明，在非晶SL的热导率是较小的温度依赖性，归因于占主导地位的声子缺陷散射。
Acoustic Phonon Characteristics of Gallium Oxide Single Crystals Investigated with Brillouin-Mandelstam Light Scattering Spectroscopy
University of California, Los Angeles（加州大学洛杉矶分校）；California NanoSystems Institute, University of California, Los Angeles（加州大学洛杉矶分校加利福尼亚纳米系统研究所）；Auburn University（奥本大学）；University of California, Riverside（加州大学河滨分校）；Arizona State University（亚利桑那州立大学）
Photogeneration and signatures of coherent phonons in time-resolved photoemission spectroscopy: First-principles time-dependent adiabatic GW approach
Institute of Atomic and Molecular Sciences, Academia Sinica（原子分子科学研究所，中央研究院）；Physics Division, National Center of Theoretical Sciences（理论科学中心物理部）；Mork Family Department of Chemical Engineering and Materials Science, University of Southern California（南加州大学莫克家族化学工程与材料科学系）；Department of Physics, University of California at Berkeley（加州大学伯克利分校物理系）；Materials Sciences Division, Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室材料科学部）
Time-resolved Photo-Phonon Spectroscopy of Exchange Coupled ${Cr^{3+}}$ - Pairs in Ruby
用一种相当简单的方法，在2K温度下，同时测量了红宝石0，03 at ${%}$和0，16 at ${%}$的光吸收谱和激发态无辐射跃迁。该技术利用时间分辨的辐射热计检测声子，产生的激发态非辐射弛豫光激发与脉冲可调谐染料激光器。所观察到的声子激发光谱与已知的单个铬离子和最近邻离子对的吸收光谱相吻合。首次直接观察到单个铬离子与四近邻离子的快速（$\leqslant 0,5 μs$）共振能量转移。观察到新的强扰动$Cr$ -单离子位。
First and Second Order Raman Spectroscopy of Monoclinic $β-\mathrm{Ga}_2\mathrm{O}_{3}$
我们采用了实验和理论相结合的研究单斜$β$ -Ga $_{2}$ O $_{3}$的一阶和二阶拉曼模式。所研究的材料由于其深紫外带隙与高临界场强配对而特别令人感兴趣，在电力电子学中提供了有前途的应用。一个关键的先决条件，为未来发展的Ga $_{2}$ O $_{3}$为基础的设备是一个详细的了解晶格动力学，因为它们是重要的弹性（通过声学声子），导热性（通过声子传递的热量），温度依赖性的带隙（受电子-声子耦合）或自由载流子传输（通过声子散射）。在（010）和（$\bar{2}01$）平面上的偏振显微拉曼光谱测量能够确定所有15个一阶和40多个二阶拉曼模式的声子频率。实验结果与用密度泛函微扰理论（DFPT）计算的模式频率、声子色散关系和声子态密度相关联。通过应用群论分析，我们能够区分泛音和组合模式，并确定在布里渊区的高对称点，有助于观察到的二阶模式。基于这些信息，我们演示了同时测定拉曼，红外，和声学声子在$β$ -Ga $_{2}$ O $_{3}$的二阶拉曼光谱。
Temperature evolution of quasiparticle dispersion dynamics in semimetallic 1T-TiTe2 via high-resolution angle-resolved photoemission spectroscopy and ultrafast optical pump-probe spectroscopy
Experimental Determination of Electron Transition Probabilities in Elementary Electron-Phonon Scattering Processes Using Electron-Energy-Loss Spectroscopy: The Example of Graphite
