长程关联无序偏置晶格中的带内激子弛豫
Intraband exciton relaxation in a biased lattice with long-range correlated disorder
摘要：
我们数值研究了线性偏压下一维无标度无序晶格中的带内激子弛豫。激子输运被认为是静态晶格本征态上的非相干跳跃。无偏格点的位势与幂律谱密度$S(k) \sim 1/k^α$、$α> 0$长程相关。如果$α$大于临界值$α_c$，晶格支持带中心处的扩展态的相位[F. A. B. F. de Dalla和M. L. Lyra，Phys. Rev. Lett. \textbf{81}，3735（1998）]。当施加偏压时，吸收光谱显示出Wannier-Stark阶梯的清晰特征[E. \emph{et al.}，Phys. Rev. \textbf{73}，172410（2006）]。我们证明了在无偏格点和弱关联势中的衰减规律是非指数的。然而，当偏置增加并且$α$较大时，衰减是纯指数的。我们将这种指数衰减与激子带中的Wannier-Stark阶梯的发生联系起来。
英文摘要：
We study numerically the intraband exciton relaxation in a one-dimensional lattice with scale-free disorder, in the presence of a linear bias. Exciton transport is considered as incoherent hoppings over the eigenstates of the static lattice. The site potential of the unbiased lattice is long-range-correlated with a power-law spectral density $S(k) \sim 1/k^α$, $α> 0$. The lattice supports a phase of extended states at the center of the band, provided $α$ is larger than a critical value $α_c$ [F. A. B. F. de Moura and M. L. Lyra, Phys. Rev. Lett. \textbf{81}, 3735 (1998)]. When the bias is applied, the absorption spectrum displays clear signatures of the Wannier-Stark ladder [E. D\'ıaz \emph{et al.}, Phys. Rev. B\textbf{73}, 172410 (2006)]. We demonstrate that in unbiased lattices and in weakly correlated potentials the decay law is non-exponential. However, the decay is purely exponential when the bias increases and $α$ is large. We relate this exponential decay to the occurrence of the Wannier-Stark ladder in the exciton band.
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