论文标题
弱耦合处的非谐波大极化气体的光学电导率
Optical conductivity of an anharmonic large polaron gas at weak coupling
论文作者
论文摘要
在极性固体中，电子或其他电荷载体可以与离子晶格的声子相互作用，从而导致偏极粒子的形成。材料的光学传导率和光吸收光谱受到该电子音波耦合的影响，最著名的是导致中红外区域的吸收峰。最近，得出了一种用于Anharmonic电子波耦合的模型哈密顿量[M. Houtput和J. Tempere，物理。 B \ textbf {103}，184306（2021）]，其中包括传统的fröhlich相互作用以及电子同时与两个声子相互作用的相互作用。在本文中，我们计算和研究了Anharmonic大极极气体的光导率，并表明由于这种1-电子-2-Phonon相互作用而出现了额外的特征吸收峰。 我们在有限温度下计算光导率$σ（ω）$的半分析表达，并使用Kubo公式进行弱耦合。电子和语音贡献可以分开分开和处理，从而可以通过众所周知的动态结构因子$ s（\ mathbf {k}，ω）$考虑电子气体的多体效应。从所得的光导率中，我们计算了极化质量，电子散射时间的估计值以及Anharmonic Polaron气体的光吸收光谱。我们表明，与著名的极性吸收峰一起，在声子能量$ \ hbarω_ {\ text {lo}} $中，1-电子-2-Phonon相互作用会导致额外的吸收峰值在$ 2 \ hbarω_ {\ text {\ text {lo}} $中。我们将这种吸收峰作为一种实验可测量的指标，用于材料中不可忽略的1-电子-2-phonon相互作用，因为该峰的高度与这种无声相互作用的强度成正比。
In a polar solid, electrons or other charge carriers can interact with the phonons of the ionic lattice, leading to the formation of polaron quasiparticles. The optical conductivity and optical absorption spectrum of a material are affected by this electron-phonon coupling, most notably leading to an absorption peak in the mid-infrared region. Recently, a model Hamiltonian for anharmonic electron-phonon coupling was derived [M. Houtput and J. Tempere, Phys. Rev. B \textbf{103}, 184306 (2021)], that includes both the conventional Fröhlich interaction as well an interaction where an electron interacts with two phonons simultaneously. In this article, we calculate and investigate the optical conductivity of the anharmonic large polaron gas, and show that an additional characteristic absorption peak appears due to this 1-electron-2-phonon interaction. We calculate a semi-analytical expression for the optical conductivity $σ(ω)$ at finite temperatures and weak coupling using the Kubo formula. The electronic and phononic contributions can be split and treated separately, such that the many-body effects of the electron gas may be taken into account through the well-known dynamical structure factor $S(\mathbf{k},ω)$. From the resulting optical conductivity, we calculate the polaron effective mass, an estimate for the electron-phonon scattering times, and the optical absorption spectrum of the anharmonic polaron gas. We show that alongside the well-known polaron absorption peak at the phonon energy $\hbar ω_{\text{LO}}$, the 1-electron-2-phonon interaction leads to an additional absorption peak at $2 \hbar ω_{\text{LO}}$. We propose this absorption peak as an experimentally measurable indicator for nonnegligible 1-electron-2-phonon interaction in a material, since the height of this peak is proportional to the strength of this anharmonic interaction.
