双钙钛矿 Cs2NaFeCl6 中的晶格动力学和电子-声子耦合,The Journal of Physical Chemistry C

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双钙钛矿 Cs2NaFeCl6 中的晶格动力学和电子-声子耦合
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2023-01-19 , DOI: 10.1021/acs.jpcc.2c07493
Bin Zhang ₁ , Johan Klarbring ₁ , Fuxiang Ji _{1,

2} , Sergei I Simak _{1,

2} , Igor A Abrikosov ₁ , Feng Gao ₁ , Galyna Yu Rudko ₁ , Weimin M Chen ₁ , Irina A Buyanova ₁

Affiliation

声子-声子和电子/激子-声子耦合在金属卤化物钙钛矿的热、电子和光学特性中起着至关重要的作用。在这项工作中，我们评估了新型双钙钛矿 Cs ₂ NaFeCl ₆单晶中的声子非谐性和电子与振动激发之间的耦合。通过采用全面的拉曼测量与第一性原理理论计算相结合，我们确定了四种拉曼活性振动模式。这些模式的偏振特性意味着Fm 3̅ m晶格的对称性，表示晶格中 Fe 和 Na 原子的平均有序分布。我们进一步表明，拉曼模式的温度依赖性，例如声子线宽及其能量的变化，表明高声子非谐性，这是双钙钛矿材料的典型特征。共振多声子拉曼散射揭示了高能带态的存在，这些能带态介导强电子-声子耦合并产生高达五阶的强烈nA _{1 g泛音。}_{Cs 2} NaFeCl ₆中的强电子-声子耦合还根据吸收系数的 Urbach 尾部分析和计算的 Fröhlich 耦合常数得出结论。因此，我们的结果表明声子-声子和电子-声子相互作用对 Cs ₂ NaFeCl ₆的电子特性有显着影响，这对于这种新型材料的潜在应用很重要。

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Lattice Dynamics and Electron–Phonon Coupling in Double Perovskite Cs2NaFeCl6

Phonon–phonon and electron/exciton–phonon coupling play a vitally important role in thermal, electronic, as well as optical properties of metal halide perovskites. In this work, we evaluate phonon anharmonicity and coupling between electronic and vibrational excitations in novel double perovskite Cs₂NaFeCl₆ single crystals. By employing comprehensive Raman measurements combined with first-principles theoretical calculations, we identify four Raman-active vibrational modes. Polarization properties of these modes imply Fm3̅m symmetry of the lattice, indicative for on average an ordered distribution of Fe and Na atoms in the lattice. We further show that temperature dependence of the Raman modes, such as changes in the phonon line width and their energies, suggests high phonon anharmonicity, typical for double perovskite materials. Resonant multiphonon Raman scattering reveals the presence of high-lying band states that mediate strong electron–phonon coupling and give rise to intense nA_1g overtones up to the fifth order. Strong electron–phonon coupling in Cs₂NaFeCl₆ is also concluded based on the Urbach tail analysis of the absorption coefficient and the calculated Fröhlich coupling constant. Our results, therefore, suggest significant impacts of phonon–phonon and electron–phonon interactions on electronic properties of Cs₂NaFeCl₆, important for potential applications of this novel material.

更新日期：2023-01-19

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