标题： 门控二维半导体纳米结中的热电优化和量子到经典跃迁 显示英文标题

标题： Thermoelectric optimization and quantum-to-classical crossover in gate-controlled two-dimensional semiconducting nanojunctions

摘要： 我们使用第一性原理模拟，包括密度泛函理论、DFT与非平衡格林函数形式（nanoDCAL）以及非平衡分子动力学模拟的组合，研究了具有门控可调结构和不同通道长度（从3到12纳米）的二维纳米结的热电性能。 我们的研究揭示了电子传输中从量子到经典的门控、温度和长度依赖性转变，短结中的量子隧穿过渡到长结中的热电子发射。 由于这种交叉和门控控制，热电优值的非平凡依赖关系体现在塞贝克系数、电导率和热导率上。 我们发现，最大化ZT需要将化学势调整到带隙之外，此时系统处于绝缘和导电区域之间的过渡状态。 尽管在绝缘状态下观察到了非常大的塞贝克系数，但由于电导率被抑制和主要的声子热传导，它们并未产生高ZT。 在500 K时，最短的3纳米结实现了大于2.3的最优ZT，此时量子隧穿和热电子发射共存。 这些发现为二维半导体纳米结中的输运机制提供了基本见解，并为高效纳米尺度热电设备的设计提供了原则。 显示英文摘要

摘要： We investigate the thermoelectric performance of 2D nanojunctions with gate tunable architectures and varying channel lengths from 3 to 12 nm using a combination of first principles simulations, including density functional theory, DFT with nonequilibrium Greens function formalism (nanoDCAL), and nonequilibrium molecular dynamics simulations. Our study reveals a gate, temperature, and length dependent transition from quantum to classical in electron transport, transitioning from quantum tunneling in short junctions to thermionic emission in longer ones. We observe nontrivial dependencies of the thermoelectric figure of merit on the Seebeck coefficient, electrical conductivities, and thermal conductivities as a result of this crossover and gate controlling. We identify that maximizing ZT requires tuning the chemical potential just outside the band gap, where the system lies at the transition between insulating and conducting regimes. While extremely large Seebeck coefficients are observed in the insulating state, they do not yield high ZT due to suppressed electrical conductivity and dominant phononic thermal transport. The optimal ZT larger than 2.3 is achieved in the shortest 3 nm junction at 500 K, where quantum tunneling and thermionic emission coexist. These findings offer fundamental insights into transport mechanisms in 2D semiconducting nanojunctions and present design principles for high efficiency nanoscale thermoelectric devices.