摘要
在太阳能转化过程中,激发态热载流子的动力学行为决定了能量转化的效率.我们采用动量空间非绝热分子动力学(NAMD_k)方法研究了金红石TiO_(2)体系中的热电子弛豫过程.研究中,我们选择了两种初始能量的热电子,其动量都位于Γ点,能量分别为Eini=0.64 eV和Eini=2.75 eV.结果显示,热电子弛豫过程主要包括两个阶段:(1)首先,热电子被散射到第一布里渊区的等能面上,形成热电子系综,此过程能量基本保持不变,只有动量发生变化,称为动量弛豫过程.对于Eini=0.64 eV和Eini=2.75 eV两种情况,动量弛豫时间均在15–25 fs之间;(2)随后,热电子系综作为一个整体逐渐弛豫至导带底,这一阶段称为能量弛豫过程,其中Eini=0.64 eV和Eini=2.75 eV的能量弛豫时间分别为39和97 fs.在热电子弛豫过程中,其能量通过电声耦合转移给体系晶格,激发更多的声子,TiO_(2)是一种离子晶体,在热电子弛豫过程中,Fröhlich电声耦合起到了关键作用,导致大部分热电子的能量转移至Γ点的A1g声子,激发了Ti‒O拉伸的纵光学支声子.我们的研究为理解金红石TiO_(2)体内的热电子弛豫与能量转化过程提供了新的理论基础.
In the process of solar energy conversion,the dynamics of excited hot carriers are crucial in determining the efficiency of energy transfer.We investigated hot electron relaxation in rutile TiO_(2) using the non-adiabatic molecular dynamics in momentum space(NAMD_k)method.In this study,we choose hot electrons with two different initial energies(Eini=0.64 eV and Eini=2.75 eV),each with momentum located at theΓpoint,to study their relaxation dynamics.The results show that the hot electron relaxation process mainly involves two stages:(1)First,the hot electrons are scattered to the iso-energy surface within the first Brillouin zone,forming the hot electron ensemble,which can be understood as the momentum relaxation process.For Eini=0.64 eV and Eini=2.75 eV,the momentum relaxation ranges from 15 to 25 fs.(2)Subsequently,the hot electron ensemble as a whole gradually relaxes to the conduction band minimum which can be understood as the energy relaxation process.Here,the energy relaxation time of Eini=0.64 eV and Eini=2.75 eV are 39 and 97 fs,respectively.During the hot electron relaxation,energy is transferred to the TiO_(2) lattice through electron-phonon coupling.As an ionic crystal,Fröhlich type electron-phonon coupling plays a key role in the hot electron relaxation,causing most of the energy of the hot electrons to be transferred to the A1g phonons,which corresponds to the Ti‒O stretching longitudinal optical phonon.Our study provides new physical insights for understanding the hot electron relaxation and energy conversion processes in rutile TiO_(2).
作者
师展
郑镇法
郑奇靖
赵瑾
SHI Zhan;ZHENG ZhenFa;ZHENG QiJing;ZHAO Jin(Department of Physics,University of Science and Technology of China,Hefei 230026,China;Key Laboratory of Precision and Intelligent Chemistry,University of Science and Technology of China,Hefei 230026,China;Hefei National Laboratory,University of Science and Technology of China,Hefei 230088,China;Hefei National Research Center for Physical Sciences at the Microscale,University of Science and Technology of China,Hefei 230026,China;Department of Physics and Astronomy,University of Pittsburgh,Pittsburgh 15260,USA)
出处
《中国科学:物理学、力学、天文学》
北大核心
2025年第1期109-117,共9页
Scientia Sinica Physica,Mechanica & Astronomica
基金
国家自然科学基金(编号:12125408,12334004,12174363)
科技部量子通信与量子计算机重大项目(编号:2021ZD0303306)
中国科学院战略性先导科技专项(编号:XDB0450101)资助项目。
关键词
第一性原理计算
电声耦合
热电子弛豫
动量空间非绝热分子动力学
first principles calculations
electron-phonon coupling
hot electron relaxation
non-adiabatic molecular dynamics in momentum space
作者简介
联系人:郑镇法,E-mail:zzfgjs@mail.ustc.edu.cn;联系人:郑奇靖,E-mail:zqj@ustc.edu.cn;联系人:赵瑾,E-mail:zhaojin@ustc.edu.cn。
