Optical properties of (SrMnO₃)n/(LaMnO₃)₂n superlattices: an insulator-to-metal transition observed in the absence of disorder.

Perucchi, Andrea; Baldassarre, Leonetta; Nucara, Alessandro; Calvani, Paolo; Adamo, Carolina; Schlom, Darrell G; Orgiani, Pasquale; Maritato, Luigi et al. · Nano Lett · 2010

basic_science · Level V

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Abstract

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.