Arora Ashish, Drüppel Matthias, Schmidt Robert, Deilmann Thorsten, Schneider Robert, Molas Maciej R, Marauhn Philipp, Michaelis de Vasconcellos Steffen, Potemski Marek, Rohlfing Michael, Bratschitsch Rudolf
Institute of Physics and Center for Nanotechnology, University of Münster, Wilhelm-Klemm-Strasse 10, 48149, Münster, Germany.
Institute of Solid State Theory, University of Münster, Wilhelm-Klemm-Strasse 10, 48149, Münster, Germany.
Nat Commun. 2017 Sep 21;8(1):639. doi: 10.1038/s41467-017-00691-5.
Bound electron-hole pairs called excitons govern the electronic and optical response of many organic and inorganic semiconductors. Excitons with spatially displaced wave functions of electrons and holes (interlayer excitons) are important for Bose-Einstein condensation, superfluidity, dissipationless current flow, and the light-induced exciton spin Hall effect. Here we report on the discovery of interlayer excitons in a bulk van der Waals semiconductor. They form due to strong localization and spin-valley coupling of charge carriers. By combining high-field magneto-reflectance experiments and ab initio calculations for 2H-MoTe, we explain their salient features: the positive sign of the g-factor and the large diamagnetic shift. Our investigations solve the long-standing puzzle of positive g-factors in transition metal dichalcogenides, and pave the way for studying collective phenomena in these materials at elevated temperatures.Excitons, quasi-particles of bound electron-hole pairs, are at the core of the optoelectronic properties of layered transition metal dichalcogenides. Here, the authors unveil the presence of interlayer excitons in bulk van der Waals semiconductors, arising from strong localization and spin-valley coupling of charge carriers.
被称为激子的束缚电子 - 空穴对支配着许多有机和无机半导体的电学和光学响应。具有电子和空穴空间位移波函数的激子（层间激子）对于玻色 - 爱因斯坦凝聚、超流性、无耗散电流流动以及光致激子自旋霍尔效应具有重要意义。在此，我们报告了在体范德华半导体中发现层间激子的情况。它们是由于电荷载流子的强局域化和自旋 - 谷耦合而形成的。通过结合对2H - MoTe的高场磁反射实验和从头算计算，我们解释了它们的显著特征：g因子的正号和大的抗磁位移。我们的研究解决了过渡金属二卤化物中g因子为正这一长期存在的难题，并为在高温下研究这些材料中的集体现象铺平了道路。激子作为束缚电子 - 空穴对的准粒子，是层状过渡金属二卤化物光电特性的核心。在此，作者揭示了体范德华半导体中层间激子的存在，其源于电荷载流子的强局域化和自旋 - 谷耦合。
