Near-field imaging of WTe2

1.Department of Physics, Sichuan Normal University, Chengdu 610066;2.College of Physics, Sichuan University, Chengdu 610065, China;3.State Key Laboratory of Applied Surface Physics, Fudan University, Shanghai 200438, China;4.Department of Physics, Fudan University, Shanghai 200438, China

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Supported by National Natural Science Foundation of China(11874271)

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    Near-field optical response of WTe2 thin films was studied by using scanning near-field optical microscopy (SNOM) , we have observed bright fringes near the edge of the thin film sample and also a thickness dependence on optical contrast to the sample and substrate. To understand this behavior, first we obtain the dielectric function of WTe2 at room temperature by Drude-Lorentz model via fitting the infrared radiation (IR) reflectance and conductivity spectra, then the near-field ratio of thin film sample to the diamond substrate is calculated by the Finite-dipole model. The experimental result reveals that the behavior of the sample cannot be fully described by the bulk properties. We assume that a decoupled thin layer exists on the surface of the bulk. There are two possible explanations for the observation of the near-field patterns of bright outside fringes. Firstly, a hot-spot field may be produced between the tip and the sample edge due to the enhancement of the local electric field under the IR illumination, a similar behavior has been revealed in surface-metallic black phosphorus. Another probability is that the topological edge states of top decoupled monolayer WTe2 lead to an enhancement of the local optical conductivity. This work provides a reference from the optical research of topological materials in the future.

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DAI Zhen-Bing, LUO Guo-Yu, HE Yan, WANG Chong, YAN Hu-Gen, LI Zhi-Qiang. Near-field imaging of WTe2[J]. Journal of Infrared and Millimeter Waves,2022,41(2):464~469

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  • Received:March 04,2021
  • Revised:March 30,2022
  • Adopted:April 30,2021
  • Online: March 30,2022
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