Sincrotrone Trieste, Area Science Park, I-34012 Trieste, Italy.
Nano Lett. 2010 Dec 8;10(12):4819-23. doi: 10.1021/nl1022628. Epub 2010 Nov 8.
We measure the optical conductivity, σ1(ω), of (SrMnO3)n/(LaMnO3)2n superlattices (SL) for n = 1, 3, 5, and 8 and 10 < T < 400 K. Data show a T-dependent insulator to metal transition (IMT) for n ≤ 3, driven by the softening of a polaronic mid-infrared band. At n = 5 that softening is incomplete, while at the largest-period n = 8 compound the MIR band is independent of T and the SL remains insulating. One can thus first observe the IMT in a Manganite system in the absence of the disorder due to chemical doping. Unsuccessful reconstruction of the SL optical properties from those of the original bulk materials suggests that (SrMnO3)n/(LaMnO3)2n heterostructures give rise to a novel electronic state.
我们测量了 (SrMnO3)n/(LaMnO3)2n 超晶格（SL）的光学电导率 σ1(ω)，其中 n = 1、3、5 和 8，10 < T < 400 K。数据显示，n ≤ 3 时存在温度依赖的绝缘到金属转变（IMT），由极化子中红外带的软化驱动。在 n = 5 时，这种软化不完整，而在最大周期 n = 8 的化合物中，MIR 带与 T 无关，SL 保持绝缘。因此，人们可以在没有化学掺杂引起的无序的情况下首次在锰氧化物系统中观察到 IMT。从原始体材料的光学性质重建 SL 光学性质的不成功表明 (SrMnO3)n/(LaMnO3)2n 异质结构产生了一种新的电子态。
