Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Phys Rev Lett. 2010 Jul 9;105(2):027005. doi: 10.1103/PhysRevLett.105.027005.
We report on band-dependent quasiparticle dynamics in Ba(0.6)K(0.4)Fe2As2 (Tc=37 K) measured using ultrafast pump-probe spectroscopy. In the superconducting state, we observe two distinct relaxation processes: a fast component whose decay rate increases linearly with excitation density and a slow component with an excitation density independent decay rate. We argue that these two components reflect the recombination of quasiparticles in the two hole bands through intraband and interband processes. We also find that the thermal recombination rate of quasiparticles increases quadratically with temperature. The temperature and excitation density dependence of the decays indicates fully gapped hole bands and nodal or very anisotropic electron bands.
我们报告了在 Ba(0.6)K(0.4)Fe2As2（Tc=37 K）中使用超快泵浦探测光谱测量的带依赖性准粒子动力学。在超导状态下，我们观察到两个不同的弛豫过程：一个快速分量，其衰减率随激发密度线性增加，以及一个具有与激发密度无关的衰减率的缓慢分量。我们认为这两个分量反映了通过带内和带间过程在两个空穴带中准粒子的复合。我们还发现准粒子的热复合速率随温度呈二次增加。衰减的温度和激发密度依赖性表明空穴带完全带隙和节点或非常各向异性的电子带。
