标题： 激子绝缘体Ta$_2$NiSe$_5$中超快载流子动力学的压强依赖性 显示英文标题

标题： Pressure Dependence of Ultrafast Carrier Dynamics in Excitonic Insulator Ta$_2$NiSe$_5$

摘要： 激子绝缘体（EI）相是集体多体效应的结果，其中通过电子-空穴对或激子的凝聚形成光学带隙。 我们报告了在原位几何结构中对EI Ta$_2$NiSe$_5$的压力依赖性光学泵浦光学探测光谱。 快速弛豫过程描述了从EI相到半导体的转变，压力为P$_{C_1}$ $\sim$ 1 GPa，以及从半导体到半金属相的转变，压力为P$_{C_2}$ $\sim$ 3 GPa。 在P$_{C_1}$以上的EI相的不稳定性通过引入压力下带隙减小的Rothwarf-Taylor模型来捕捉。 带隙的压力系数为65 meV/GPa，与第一性原理计算非常吻合。 显示英文摘要

摘要： An excitonic insulator (EI) phase is a consequence of collective many-body effects where an optical band gap is formed by the condensation of electron-hole pairs or excitons. We report pressure-dependent optical pump optical probe spectroscopy of EI Ta$_2$NiSe$_5$ in an on-site in situ geometry. The fast relaxation process depicts the transition across P$_{C_1}$ $\sim$1 GPa from EI phase to a semiconductor and P$_{C_2}$ $\sim$3 GPa from a semiconductor to a semimetallic phase. The instability of the EI phase beyond P$_{C_1}$ is captured by the Rothwarf-Taylor model by incorporating the decrease of the bandgap under pressure. The pressure coefficient of the bandgap decreases, 65 meV/GPa closely agrees with the first principle calculations.