Highly anisotropic and robust excitons in monolayer black phosphorus
Highly anisotropic and robust excitons in monolayer black phosphorus
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DOI：
10.1038/nnano.2015.71
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发表时间：
2015-06-01
影响因子：
38.3
通讯作者：
Xia, Fengnian
中科院分区：
文献类型：
--
作者：
Wang, Xiaomu;Jones, Aaron M.;Xia, Fengnian
半金属石墨烯和半导体单层过渡金属二硫属化物是近年来研究最深入的二维材料（1，2）。最近，黑磷由于其宽可调和直接带隙、高载流子迁移率和显著的面内各向异性电学、光学和声子性质而成为一种有前途的新二维材料（3-9）。然而，目前的进展主要限于其薄膜形式。在这里，我们揭示了高度各向异性和强烈的束缚激子在单层黑磷在室温下使用偏振分辨光致发光测量。我们发现，无论激发激光偏振，从单层发射的光是线性偏振的沿着光的有效质量方向和中心约1.3 eV，从高度各向异性的明亮的激子发射一个明确的签名。此外，光致发光激发光谱表明2.2 eV的准粒子带隙，从中我们估计类似于0.9 eV的激子结合能，与基于第一性原理的理论结果一致。实验观察到的具有大结合能的高度各向异性的明亮激子不仅为这种不寻常的二维材料中的多电子物理的未来探索开辟了道路，而且还表明了其在光电器件中的光明前景。
Semi-metallic graphene and semiconducting monolayer transition- metal dichalcogenides are the most intensively studied two-dimensional materials of recent years(1,2). Lately, black phosphorus has emerged as a promising new two-dimensional material due to its widely tunable and direct bandgap, high carrier mobility and remarkable in-plane anisotropic electrical, optical and phonon properties(3-9). However, current progress is primarily limited to its thin-film form. Here, we reveal highly anisotropic and strongly bound excitons in monolayer black phosphorus using polarization-resolved photoluminescence measurements at room temperature. We show that, regardless of the excitation laser polarization, the emitted light from the monolayer is linearly polarized along the light effective mass direction and centres around 1.3 eV, a clear signature of emission from highly anisotropic bright excitons. Moreover, photoluminescence excitation spectroscopy suggests a quasiparticle bandgap of 2.2 eV, from which we estimate an exciton binding energy of similar to 0.9 eV, consistent with theoretical results based on first principles. The experimental observation of highly anisotropic, bright excitons with large binding energy not only opens avenues for the future explorations of many-electron physics in this unusual two-dimensional material, but also suggests its promising future in optoelectronic devices.