The vibrational properties of ferrimagnetic $\mathrm{Mn_3Si_{2}Te_6}$ single crystals are investigated using Raman spectroscopy and density functional theory calculations. Eighteen Raman-active modes are identified, fourteen of which are assigned according to with the trigonal symmetry. Four additional peaks, obeying the $A_{1g}$ selection rules, are attributed to the overtones. The unconventional temperature evolution of the $A_{1g}^5$ mode self-energy suggests a competition between different short-range magnetic correlations that significantly impact the spin-phonon interaction in $\mathrm{Mn_3Si_{2}Te_6}$. The research provides a comprehensive insight to the lattice properties, studies their temperature dependence and shows the arguments for existence of competing short-range magnetic phases in $\mathrm{Mn_3Si_{2}Te_6}$.
We calculate the lattice dielectric function of strongly anharmonic rutile $\mathrm{TiO}_2$ from ab initio anharmonic lattice dynamics methods. Since an accurate calculation of the $Γ$ point phonons is essential for determining optical properties, we employ the modified self-consistent approach, including third-order anharmonicity as well as fourth-order anharmonicity. The resulting optical phonon frequencies and linewidths at the $Γ$ point much better agree with experimental measurements than those from a perturbative approach. We show that the four-phonon scattering process contributes as mu…
An ultrafast atomic motion of a photo-induced coherent phonon of bismuth at low temperatures was directly observed with time-resolved x-ray diffraction. A cryostat with a window that is transparent to both optical lasers and x-rays enabled versatile diffraction measurements in a wide temperature range including below 10 K. It is found that an atomic displacement in a fully symmetric A$_{\mathrm{1g}}$ phonon mode is suppressed at low temperatures. This result indicates the displacive excitation process is suppressed in the phonon generation with decreasing temperature.
High-Throughput Discovery of Chiral Carbon-Boron Semimetals with Weyl Topology and Phonon-Mediated Superconductivity
University of Science and Technology of China（中国科学技术大学）；Wuhan Institute of Technology（武汉工程大学）；Hefei University of Technology（合肥工业大学）；Hanhai Lingchao Intelligent Computing (Shanghai) Technology Services Co., Ltd.（瀚海凌潮智能计算（上海）科技有限公司）
We employ a combined experimental-theoretical study of the first- and second-order Raman modes of monoclinic $β$-Ga$_{2}$O$_{3}$. The investigated materials is of particular interest due to its deep-UV bandgap paired with a high critical field strength, offering promising applications in power-electronics. A crucial prerequisite for the future development of Ga$_{2}$O$_{3}$-based devices is a detailed understanding of the lattice dynamics as they are important for the elasticity (through acoustic phonons), thermal conductivity (through the heat transferred by phonons), the temperature-dependen…
Quantitative knowledge of electron-phonon coupling is important for many applications as well as for the fundamental understanding of nonequilibrium relaxation processes. Time-resolved diffraction provides direct access to this knowledge through its sensitivity to laser-induced lattice dynamics. Here, we present an approach for analyzing time-resolved polycrystalline diffraction data. A two-step routine is used to minimize the number of time-dependent fit parameters. The lattice dynamics are extracted by finding the best fit to the full transient diffraction pattern rather than by analyzing tr…
Multiple Softening Q-vectors Driving a Cascade of CDW Phases in $\mathrm{1T-VSe}_{2}$
National Yang Ming Chiao Tung University（国立阳明交通大学）；National Taitung University（国立台东大学）；Institute of Atomic and Molecular Sciences, Academia Sinica（中央研究院原子与分子科学研究所）；National Taiwan University（国立台湾大学）；National Sun Yet-Sen University（国立中山大学）；National Central University（国立中央大学）；National Center for Theoretical Sciences（国家理论科学中心）；Tamkang University（淡江大学）；National Chung Hsing University（国立中兴大学）；National Taipei University of Technology（国立台北科技大学）
Simultaneous study of acoustic and optic phonon scattering of electrons and holes in undoped $\mathrm{GaAs}$/$\mathrm{Al_{x} Ga_{1-x} As}$ heterostructures
本研究利用非掺杂 GaAs/AlGaAs 异质结构，通过电阻率温度依赖性测量，在 1.6-92.5K 范围内同步研究了二维电子和空穴的声学与光学声子散射，提取了耦合常数和 LO 激活能，验证了该方法的有效性。
Domain Walls Stabilized by Intrinsic Phonon Modes and Engineered Defects Enable Robust Ferroelectricity in HfO2
School of Integrated Circuits, Peking University（北京大学集成电路学院）；Advanced Instrumental Analysis Center, School of Chemical Engineering and Technology, Tianjin University（天津大学化学工程与技术学院先进仪器分析中心）
In order to determine the role of non-thermal transport of hot carriers which is decisive for the dissipation of energy in condensed matter we performed time-resolved broadband femtosecond transient reflectivity measurements on $7-197 \mathrm{nm}$ thick Bi(111) films epitaxially grown on Si(111). We monitored the behavior of the Fourier amplitude and the central frequency of the coherent $A_\mathrm{1g}$ phonon mode as function of the incident fluence, film thickness, and probe wavelength in the range of $580 -700 \mathrm{nm}$. The frequency redshift that follows photoexcitation was used as a r…
The phonon density-of-states (DOS) summarizes the lattice vibrational modes supported by a structure, and gives access to rich information about the material's stability, thermodynamic constants, and thermal transport coefficients. Here, we present an atomistic line graph neural network (ALIGNN) model for the prediction of the phonon density of states and the derived thermal and thermodynamic properties. The model is trained on a database of over 14,000 phonon spectra included in the JARVIS-DFT (Joint Automated Repository for Various Integrated Simulations: Density Functional Theory) database.…
An intrinsic antiferromagnetic topological insulator $\mathrm{MnBi_2Te_4}$ can be realized by intercalating Mn-Te bilayer chain in a topological insulator, $\mathrm{Bi_2Te_3}$. $\mathrm{MnBi_2Te_4}$ provides not only a stable platform to demonstrate exotic physical phenomena, but also easy tunability of the physical properties. For example, inserting more $\mathrm{Bi_2Te_3}$ layers in between two adjacent $\mathrm{MnBi_2Te_4}$ weakens the interlayer magnetic interactions between the $\mathrm{MnBi_2Te_4}$ layers. Here we present the first observations on the inter- and intra-layer phonon modes …
Weak antiferromagnetic (AF) interaction in the ferromagnetic (FM) partially ordered La2CoMnO6 (LCMO) was detected by Raman spectroscopy by monitoring spin-phonon coupling. Because of the sensibility to probe short-range disorder and lattice modifications, the Raman spectroscopy showed to be an useful tool to indicate less remarkable magnetic transitions in LCMO compound. Apart from the expected spin-phonon coupling due to the long-range FM superexchange (Tc~230 K), phonons parameters pointed out an additional spin-phonon coupling related to the short-range AF interaction at Tc~135 K, which was…
Ultrafast dynamics of the low frequency shear mode in $\mathrm{1T'-MoTe_2}$
本文报道了利用飞秒泵浦-探测光谱研究半金属1 T '-MoTe 2中相干声子的动力学。在室温下的超快亚皮秒时间尺度上，在0.39 THz处观察到低频和长寿命的剪切声子模式，这是以前报道的仅在低温Td-MoTe 2相中以特征声子的形式存在。与其他光学声子模不同，剪切声子模与光激发载流子强耦合。此外，剪切模式的振幅令人惊讶地随着激发密度的增加而降低，这种现象可以归因于激发后晶格温度升高的结果。这些结果提供了有用的物理信息之间的正常的半金属1 T '和晶格反转对称性破缺II型Weyl半金属Td相的超快晶格对称性切换。
Electron-lattice interactions play a prominent role in quantum materials, making a deeper understanding of direct routes to phonon-mediated high-transition-temperature ($T_{\mathrm{c}}$) superconductivity desirable. However, it has been known for decades that weak electron-phonon coupling gives rise to low values of $T_{\mathrm{c}}$, while strong electron-phonon coupling leads to lattice instability or formation of bipolarons, generally assumed to be detrimental to superconductivity. Thus, the route to high-$T_{\mathrm{c}}$ materials from phonon-mediated mechanisms has heretofore appeared to b…
We report on the coherent phonon spectroscopy of polymorphic $\mathrm{MoTe_2}$ single crystals using a femtosecond-pulsed laser to investigate the relationship between structural phase transitions and photo-thermal effects induced by high-density laser excitation. Even when a femtosecond pulsed laser was used, which generally induces fewer heat accumulation effects than the case for a CW laser, tellurium segregation was observed in coherent phonon spectra with increasing excitation density, while no structural phase transition among polymorphs of $\mathrm{MoTe_2}$ was observed. The use of high…
Phonons reflect dynamic spin-state order in LaCoO$_3$
Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院）；RIKEN（理化学研究所）；SPring-8/JASRI（SPring-8/日本同步辐射研究所）；Physikalisches Institut, Karlsruhe Institute of Technology（卡尔斯鲁厄理工学院物理研究所）；Karlsruhe Nano Micro Facility (KNMFi), Karlsruhe Institute of Technology（卡尔斯鲁厄纳米微设施，卡尔斯鲁厄理工学院）；Laboratoire Léon Brillouin (CEA-CNRS)（莱昂·布里渊实验室）；Institut Laue-Langevin（朗之万研究所）；Argonne National Laboratory（阿贡国家实验室）；Jülich Centre for Neutron Science (JCNS), Forschungszentrum Jülich GmbH（于利希中子科学中心）；Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München（海因茨·迈尔-莱布尼茨中心，慕尼黑工业大学）
Mode-selective electron-phonon coupling drives charge density waves in the kagome metals YRu$_3$Si$_2$ and LaRu$_3$Si$_2$
Key Laboratory of Materials Physics, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院固体物理研究所材料物理重点实验室）；University of Science and Technology of China（中国科学技术大学）；High Magnetic Field Laboratory, HFIPS, Chinese Academy of Sciences（中国科学院合肥物质科学研究院高磁场实验室）；Collaborative Innovation Center of Microstructures, Nanjing University（南京大学微结构协同创新中心）
Short-Range Structure and Phonon Assignment of the Brownmillerite-Type Oxide Ba$_{2}$In$_{2}$O$_{5}$ and its Hydrated Proton-Conducting Form BaInO$_{3}$H
利用拉曼、红外和非弹性中子散射光谱以及密度泛函理论计算研究了钙钛矿型氧化物Ba $_{2}$ In $_{2}$ O $_{5}$及其水合形式BaInO $_{3}$ H的振动光谱和短程结构。对于Ba $_{2}$ In $_{2}$ O $_{5}$，其可以被描述为具有InO $_{6}$八面体和InO $_{4}$四面体的交替层的缺氧钙钛矿结构，结果证实了$Icmm$对称性的短程结构，其特征在于InO $_{4}$四面体的连续层的随机取向。对于水合质子传导形式BaInO $_{3}$ H，结果表明短程结构比先前基于中子衍射提出的$P4/mbm$对称性更复杂，而是表明质子构型接近Martinez等人预测的最低能量结构[J.- R.马丁内斯角E. Moen，S. Stoelen，N. L. Allan，J. of Solid State Chem.180，3388，（2007）]。一个强烈的拉曼活性振动在150厘米$^{-1}$被确定为一个独特的指纹，这种质子配置。
