Electronic contribution to thermal conductivity ( κ e) is proportional to electrical conductivity ( σ) as given by the Wiedemann–Franz law ( κ e = L σ T). The Lorenz number ( L) scales the thermal current associated with the electrical current and implies the electrons' capability of carrying heat. By experimental transport measurements and first-principles calculations, we show that electron transport overwhelmingly dominates thermal conductivity in β-Ag2Se, which has intrinsically low lattice thermal conductivity. The Lorenz number linearly decreases from Ag1.95Se to Ag2.03Se, as the point defect changes from a cation vacancy to a self-interstitial. This striking behavior reveals the inelastic electron scattering process due to nonstoichiometry point defects and suggests that the cation vacancies increase while self-interstitials reduce the amount of heat carried by electrons. Remarkably, the Lorenz number varies by 40% for such a narrow nonstoichiometry window, with the deviation as large as 36% from the Sommerfeld value. Finally, we predict the maximum Lorenz number that can be achieved in β-Ag2Se for various electron scattering mechanisms. This work provides insights into the physics of electronic heat conduction in solids containing point defects.

中文翻译：

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非化学计量点缺陷对电子热导率的影响

电子对热导率 (κ e) 的贡献与电导率 (σ) 成正比，如 Wiedemann-Franz 定律 (κ e = L σ T)。洛伦兹数 (L) 缩放与电流相关的热电流，并暗示电子携带热量的能力。通过实验输运测量和第一性原理计算，我们表明电子输运在 β-Ag2Se 中压倒性地主导了热导率，β-Ag2Se 具有固有的低晶格热导率。随着点缺陷从阳离子空位变为自填隙，洛伦兹数从 Ag1.95Se 线性减小到 Ag2.03Se。这种惊人的行为揭示了由于非化学计量点缺陷导致的非弹性电子散射过程，并表明阳离子空位增加而自填隙减少了电子携带的热量。值得注意的是，对于如此狭窄的非化学计量窗口，洛伦兹数的变化幅度为 40%，与索末菲值的偏差高达 36%。最后，我们预测了各种电子散射机制在 β-Ag2Se 中可以实现的最大洛伦兹数。这项工作提供了对包含点缺陷的固体中电子热传导物理学的见解。我们预测了各种电子散射机制在 β-Ag2Se 中可以实现的最大洛伦兹数。这项工作提供了对包含点缺陷的固体中电子热传导物理学的见解。我们预测了各种电子散射机制在 β-Ag2Se 中可以实现的最大洛伦兹数。这项工作提供了对包含点缺陷的固体中电子热传导物理学的见解。