Valley-Selective Exciton Bistability in a Suspended Monolayer Semiconductor,Nano Letters

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Valley-Selective Exciton Bistability in a Suspended Monolayer Semiconductor
Nano Letters ( IF 9.6 ) Pub Date : 2018-04-16 00:00:00 , DOI: 10.1021/acs.nanolett.8b00987
Hongchao Xie _{1,

2} , Shengwei Jiang ₁ , Jie Shan _{1,

3} , Kin Fai Mak _{1,

3}

Affiliation

We demonstrate robust optical bistability, the phenomenon of two well-discriminated stable states depending upon the history of the optical input, in fully suspended monolayers of WSe₂ at low temperatures near the exciton resonance. Optical bistability has been achieved under continuous-wave optical excitation that is red-detuned from the exciton resonance at an intensity level of 10³ W/cm². The observed bistability is originated from a photothermal mechanism, which provides both optical nonlinearity and passive feedback, two essential elements for optical bistability. The low thermal conductance of suspended samples is primarily responsible for the low excitation intensities required for optical bistability. Under a finite out-of-plane magnetic field, the exciton bistability becomes helicity dependent due to the exciton valley Zeeman effect, which enables repeatable switching of the sample reflectance by light polarization. Our study has opened up exciting opportunities in controlling light with light, including its wavelength, power, and polarization, using monolayer semiconductors.

中文翻译：

悬浮单层半导体中的谷选择性激子双稳态

我们在激子共振附近的低温下，在WSe _2的完全悬浮单分子层中，证明了稳健的光学双稳态性，这是两个完全区分的稳定状态的现象，取决于光学输入的历史。在以10 ³ W / cm ²的强度水平从激子共振红色失谐的连续波光学激发下，已经实现了光学双稳性。观察到的双稳态性源自光热机制，该机制提供了光学非线性和被动反馈，这是光学双稳态性的两个基本要素。悬浮样品的低热导率是造成光学双稳态所需的低激发强度的主要原因。在有限的平面外磁场下，由于激子谷的塞曼效应，激子的双稳性变得依赖于螺旋度，这使得能够通过光偏振可重复地切换样品的反射率。我们的研究为使用单层半导体控制光（包括波长，功率和偏振）开辟了令人兴奋的机会。

更新日期：2018-04-16

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