Departments of Physics and Electrical Engineering, Columbia University, New York, New York 10027, USA.
Department of Mechanical Engineering, Columbia University, New York, New York 10027, USA.
Phys Rev Lett. 2015 Sep 18;115(12):126802. doi: 10.1103/PhysRevLett.115.126802. Epub 2015 Sep 16.
We demonstrate continuous tuning of the exciton binding energy in monolayer WS_{2} by means of an externally applied voltage in a field-effect transistor device. Using optical spectroscopy, we monitor the ground and excited excitonic states as a function of gate voltage and track the evolution of the quasiparticle band gap. The observed decrease of the exciton binding energy over the range of about 100 meV, accompanied by the renormalization of the quasiparticle band gap, is associated with screening of the Coulomb interaction by the electrically injected free charge carriers at densities up to 8×10^{12} cm^{-2}. Complete ionization of the excitons due to the electrical doping is estimated to occur at a carrier density of several 10^{13} cm^{-2}.
我们通过在场效应晶体管器件中施加外部电压，证明了单层 WS_{2} 的激子结合能可以连续调节。我们利用光学光谱学，监测了作为栅极电压函数的基态和激发激子态，并跟踪了准粒子带隙的演化。观察到的激子结合能在约 100meV 的范围内减小，同时准粒子带隙的重整化，与在高达 8×10^{12}cm^{-2}的密度下通过电注入的自由电荷载流子屏蔽库仑相互作用有关。由于电掺杂，激子的完全离化估计发生在载流子密度为几个 10^{13}cm^{-2}时。
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