We report an infrared ellipsometry study of the charge carrier dynamics in polycrystalline Kxp-terphenyl samples with nominal $x=3$, for which signatures of high-temperature superconductivity were previously reported. The infrared spectra are dominated by two Lorentzian bands with maxima around 4 000 cm$^{-1}$ and 12 000 cm$^{-1}$ which, from a comparison with calculations based on a Hückel model are assigned to intra-molecular excitations of $π$ electrons of the anionic p-terphenyl molecules. The inter-molecular electronic excitations are much weaker and give rise to a Drude peak and a similarly weak Lorentzian band around 220 cm$^{-1}$. A dc resistivity of about 0.3 $Ω$ cm at 300 K is deduced from the IR data, comparable to values measured by electrical resistivity on a twin sample. The analysis of the temperature dependence of the low-frequency response reveals a gradual decrease of the plasma frequency and the scattering rate of the Drude peak below 300 K that gets anomalously enhanced below 90 K. The corresponding missing spectral weight of the Drude peak appears blue-shifted towards the Lorentz-band at 220 cm$^{-1}$. This characteristic blue-shift signifies an enhanced localization of the charge carriers at low temperatures and contrasts the behavior expected for a bulk superconducting state for which the missing spectral weight would be redshifted to a delta-function at zero frequency that accounts for the loss-free response of the superconducting condensate. Our data might still be compatible with a filamentary superconducting state with a volume fraction well below the percolation limit for which the spatial confinement of the condensate can result in a plasmonic resonance at finite frequency.
Infrared dielectric function, phonon modes and free-charge carrier properties of high-Al-content Al$_x$Ga$_{1-x}$N alloys determined by mid-infrared spectroscopic ellipsometry and optical Hall effect
用中红外椭圆偏振光谱法测量了4H-SiC衬底上一组高质量Si掺杂的Al $_x$ Ga $_{1-x}$ N外延层的声子模参数和各向异性中红外介电函数张量分量。发现$E_1$（TO）模的双模行为和$A_1$（LO）模的单模行为与先前的拉曼散射光谱报告一致。建立了红外活性声子频率参数的组成依赖关系，并讨论了可能被无序激活的无声$B_1$模式。利用最佳匹配模型导出的声子模频率和高频介电常数参数，应用Lydanne-Sachs-Teller关系，确定了静态介电常数与$x$的关系。用中红外光学霍尔效应测量方法确定了高Al含量的Al-$_x$-Ga-$_{1-x}$-N合金的有效质量参数及其与成分的关系。此外，还研究了具有相似Si掺杂水平的Al-$_x$-Ga $_{1-x}$ N薄膜的自由电子浓度$N$和迁移率参数$μ$随Al含量$x$的变化关系，并进行了讨论。
Free-charge carrier parameters of n-type, p-type and compensated InN:Mg determined by Infrared Spectroscopic Ellipsometry
采用红外椭圆偏振光谱法研究了掺镁InN薄膜的自由载流子特性。比较了两组具有代表性的通过分子束外延生长的具有从$1.2\times10^{17}$ cm $^{-3}$到$8\times10^{20}$ cm $^{-3}$的Mg浓度的极性InN。P-型导电性表示的Mg浓度范围为$1\times10^{18}$ cm $^{-3}$到$9\times10^{19}$ cm $^{-3}$从纵向光学声子等离子体加宽和迁移率参数的Mg浓度的依赖性的系统调查。一个参数化的模型，占的声子-等离子体激元耦合被施加到确定的自由载流子浓度和迁移率参数的掺杂的块状InN层，以及GAN模板和未掺杂的InN缓冲层为每个样品。第二样品组中的自由载流子性质与先前报道的第一样品组的综合分析中确定的结果一致[Schöche等人，J. Appl.Phys.113，013502（2013）]。在第二组中，具有$2.3\times10^{20}$ cm $^{-3}$的Mg浓度的两个样品被识别为具有非常低的电子浓度的补偿n型InN，其适合于进一步研究通常由高电子浓度控制的本征材料性质，即使在未掺杂的InN中。补偿的n型InN样品可以清楚地从类似的等离子体频率的p型导电材料的强烈减少的声子等离子体激元展宽区分。
Hole concentrations in doped gray α-Sn on InSb and CdTe measured with infrared ellipsometry
New Mexico State University（新墨西哥州立大学）；Charles University, Faculty of Mathematics and Physics（查理大学数学物理学院）；University of California Santa Barbara（加州大学圣塔芭芭拉分校）
Infrared ellipsometry study of the photo-generated charge carriers at the (001) and (110) surfaces of SrTiO$_3$ crystals and the interface of corresponding LaAlO$_3$/SrTiO$_3$ heterostructures
Electronic localization on the structural inhomogeneities formed due to Bi and Te deficiency in the MBE grown films of AFM topological insulator MnBi2Te4: Evidence from spectroscopic ellipsometry and infrared studies
Anisotropy, phonon modes, and free charge carrier parameters in monoclinic $β$-gallium oxide single crystals
我们推导了一种介电函数张量模型方法，用于描述具有多个非耦合红外和远红外激活模的单斜和三斜对称材料的光学响应。我们将我们的模型方法应用于单斜晶系的$β$ -Ga $_2$ O $_3$单晶样品.本文用广义椭圆偏振光谱法研究了大块晶体（010）和（$\bar{2}$ 01）在不同角度下切割的表面在红外和远红外波段的光谱特性。我们确定了4个独立的$β$ -Ga $_2$ O $_3$笛卡尔介电函数张量元素的频率依赖性匹配的大组实验数据，使用逐点数据反演方法。通过将我们的单斜模型与所得到的4个介电函数张量分量相匹配，我们确定了单斜晶格中所有具有$A_u$和$B_u$对称性的红外和远红外主动横光学声子模及其本征矢量。我们发现我们的模型结果和密度泛函理论计算结果之间非常吻合。我们导出并讨论了$β$ -Ga $_2$ O $_3$中的纵光学声子的频率.我们推导和报告的密度和各向异性迁移率参数的自由载流子内掺锡晶体。讨论了$β$ -Ga $_2$ O $_3$中纵声子等离子体激元耦合模的出现，给出了它们的频率和本征矢量.我们还讨论并提出了单斜介电常数的静态电场和频率以上的reststrahlen范围内，我们提供了一个概括的Lyddane-Sachs-Teller关系的单斜晶格与红外和远红外的活动模式。我们发现对于$β$ O $_3$，广义Lyddane-Sachs-Teller关系得到了很好的满足…
