布里渊区
四次方程
物理
边界(拓扑)
瞬态(计算机编程)
订单(交换)
联轴节(管道)
对称(几何)
声子
翻译(生物学)
数学物理
量子力学
数学分析
计算机科学
数学
纯数学
几何学
材料科学
冶金
生物化学
化学
财务
信使核糖核酸
基因
经济
操作系统
作者
Adrián Gómez Pueyo,Alaska Subedi
出处
期刊:Physical review
日期:2023-08-01
卷期号:108 (6)
标识
DOI:10.1103/physrevb.108.064302
摘要
${\mathrm{KTaO}}_{3}$ presents a rich hyper-Raman spectrum originating from two-phonon processes at the Brillouin zone boundary, indicating the possibility of driving these phonon modes using intense midinfrared laser sources. We obtained the coupling of light to the highest-frequency longitudinal optic phonon mode ${Q}_{\text{HY}}$ at the $X\phantom{\rule{4pt}{0ex}}(0,0,\frac{1}{2})$ point by first principles calculations of the total energy as a function of the phonon coordinate ${Q}_{\text{HY}}$ and electric field $E$. We find that the energy curve as a function of ${Q}_{\text{HY}}$ softens for finite values of electric field, indicating the presence of ${Q}_{\text{HY}}^{2}{E}^{2}$ nonlinearity with negative coupling coefficient. We studied the feasibility of utilizing this nonlinearity to transiently break the translation symmetry of the material by making the ${Q}_{\text{HY}}$ mode unstable with an intense midinfrared pump pulse. We also considered the possibility that nonlinear phonon-phonon couplings can excite the lowest-frequency phonon coordinates ${Q}_{\text{LZ}}$ and ${Q}_{\text{LX}}$ at $X$ when the ${Q}_{\text{HY}}$ mode is externally driven. The nonlinear phonon-phonon couplings were also obtained from first principles via total-energy calculations as a function of the phonon coordinates, and these were used to construct the coupled classical equations of motion for the phonon coordinates in the presence of an external pump term on ${Q}_{\text{HY}}$. We numerically solved them for a range of pump frequencies and amplitudes and found three regimes where the translation symmetry is broken: (i) rectification of the lowest-frequency coordinates due to large amplitude oscillation of the ${Q}_{\text{HY}}$ coordinate about its equilibrium position, (ii) rectification of only the ${Q}_{\text{HY}}$ coordinate without displaced oscillations of the lowest-frequency coordinates, and (iii) rectification of all three coordinates. Due to the small magnitude of the coupling constant between the ${Q}_{\text{HY}}$ mode and the electric field, the smallest value of the pump amplitude that manages to transiently break the the translation symmetry of ${\mathrm{KTaO}}_{3}$ is 270 MV/cm. Such a large value of electric field will likely cause a dielectric breakdown of the material. However, our paper shows that light-phonon coupling with negative sign can exist in real materials and motivates the search of other materials with a larger magnitude of the coupling.
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