Back Patrick, Sidler Meinrad, Cotlet Ovidiu, Srivastava Ajit, Takemura Naotomo, Kroner Martin, Imamoğlu Atac
Institute of Quantum Electronics, ETH Zürich, CH-8093 Zürich, Switzerland.
Phys Rev Lett. 2017 Jun 9;118(23):237404. doi: 10.1103/PhysRevLett.118.237404.
For applications exploiting the valley pseudospin degree of freedom in transition metal dichalcogenide monolayers, efficient preparation of electrons or holes in a single valley is essential. Here, we show that a magnetic field of 7 T leads to a near-complete valley polarization of electrons in a MoSe_{2} monolayer with a density 1.6×10^{12} cm^{-2}; in the absence of exchange interactions favoring single-valley occupancy, a similar degree of valley polarization would have required a pseudospin g factor of 38. To investigate the magnetic response, we use polarization resolved photoluminescence as well as resonant reflection measurements. In the latter, we observe gate voltage dependent transfer of oscillator strength from the exciton to the attractive Fermi polaron: stark differences in the spectrum of the two light helicities provide a confirmation of valley polarization. Our findings suggest an interaction induced giant paramagnetic response of MoSe_{2}, which paves the way for valleytronics applications.
对于利用过渡金属二硫属化物单层中的谷赝自旋自由度的应用而言，在单个谷中高效制备电子或空穴至关重要。在此，我们表明7 T的磁场会导致具有1.6×10¹² cm⁻²密度的MoSe₂单层中电子的近乎完全谷极化；在不存在有利于单谷占据的交换相互作用的情况下，类似程度的谷极化将需要38的赝自旋g因子。为了研究磁响应，我们使用偏振分辨光致发光以及共振反射测量。在后者中，我们观察到振子强度从激子到吸引性费米极化子的栅极电压依赖性转移：两种光螺旋度光谱中的显著差异证实了谷极化。我们的发现表明MoSe₂存在相互作用诱导的巨大顺磁响应，这为谷电子学应用铺平了道路。
