Spin-polarized electrons in monolayer MoS2
Spin-polarized electrons in monolayer MoS2
复制标题
DOI：
10.1038/s41565-019-0397-y
复制
发表时间：
2018-07
影响因子：
38.3
通讯作者：
J. G. Roch;G. Froehlicher;N. Leisgang;P. Makk;Kenji Watanabe;T. Taniguchi;R. Warburton
中科院分区：
文献类型：
--
作者：
J. G. Roch;G. Froehlicher;N. Leisgang;P. Makk;Kenji Watanabe;T. Taniguchi;R. Warburton
库仑相互作用是决定理想二维电子气（2DEG）在低电子密度极限下基态的关键。在这种情况下，库仑相互作用占主导地位的单粒子相空间填充。在硅和砷化镓中，电子通常局限于这些低密度。相反，在过渡金属二硫属化物（TMD），库仑相关的2DEG可以预期在实验相关的电子密度。在这里，我们研究了2DEG在门控单层的TMD二硫化钼。我们测量的光学磁化率，探针的二维电子气，这是局部的，微创和自旋选择性。在9.0 T的磁场中，电子浓度高达1.5 × 1012 cm −2，我们给出了基态是自旋极化的证据。在四个可用的导带中，只有两个被占用。这两个带具有相同的自旋，但不同的谷量子数。我们的研究结果表明，只有两个频带被占领，即使在没有磁场。自旋极化随着2DEG密度的降低而增加，这表明库仑相互作用是对称性破缺的一个关键方面。我们建议交换耦合使自旋对齐。玻尔半径是如此之小，以至于即使是在相空间中相距很远的电子也会相互作用。
Coulomb interactions are crucial in determining the ground state of an ideal two-dimensional electron gas (2DEG) in the limit of low electron densities. In this regime, Coulomb interactions dominate over single-particle phase-space filling. In silicon and gallium arsenide, electrons are typically localized at these low densities. In contrast, in transition-metal dichalcogenides (TMDs), Coulomb correlations in a 2DEG can be anticipated at experimentally relevant electron densities. Here, we investigate a 2DEG in a gated monolayer of the TMD molybdenum disulfide. We measure the optical susceptibility, a probe of the 2DEG which is local, minimally invasive and spin selective. In a magnetic field of 9.0 T and at electron concentrations up ton≃ 5 × 1012cm−2, we present evidence that the ground state is spin-polarized. Out of the four available conduction bands,, only two are occupied. These two bands have the same spin but different valley quantum numbers. Our results suggest that only two bands are occupied even in the absence of a magnetic field. The spin polarization increases with decreasing 2DEG density, suggesting that Coulomb interactions are a key aspect of the symmetry breaking. We propose that exchange couplings align the spins. The Bohr radius is so small that even electrons located far apart in phase-space interact with each other.