Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe2 on SrTiO3 (001)

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Structure, STM, and ARPES measurements of the monolayer SnSe2 grown on STO(001) | © 2020 American Chemical Society
Structure, STM, and ARPES measurements of the monolayer SnSe2 grown on STO(001). (a) Schematic view of geometric structure of the monolayer SnSe2/STO sample. (b,c) Structural model and first Brillouin zone of the monolayer SnSe2, respectively. (d) Large-area STM topographic image of the SnSe2/STO (Vbias = 2.0 V, It = 20 pA). (e) Atomic-resolution STM image of the SnSe2/STO (Vbias = −1.0 V, It = 80 pA). (f) ARPES spectra taken on the sample along the Γ−M direction in (c). (g) Second derivative of the ARPES spectra in (f). The in-gap band is marked by red arrows.
Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe2 on SrTiO3 (001) | © 2020 American Chemical Society
Interfacial Polarons in van der Waals Heterojunction of Monolayer SnSe2 on SrTiO3 (001)

Interfacial polarons have been demonstrated to play important roles in heterostructures containing polar substrates. However, most of polarons found so far are diffusive large polarons; the discovery and investigation of small polarons at interfaces are scarce. Herein, Aidi Zhao and Bing Wang et al report the emergence of interfacial polarons in monolayer SnSe2 epitaxially grown on Nb-doped SrTiO3 (STO) surface using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy (STM). ARPES spectra taken on this heterointerface reveal a nearly flat in-gap band correlated with a significant charge modulation in real space as observed with STM. An interfacial polaronic model is proposed to ascribe this in-gap band to the formation of self-trapped small polarons induced by charge accumulation and electron–phonon coupling at the van der Waals interface of SnSe2 and STO. Such a mechanism to form interfacial polaron is expected to generally exist in similar van der Waals heterojunctions consisting of layered 2D materials and polar substrates. 

Authors 

Yahui Mao, Xiaochuan Ma, Daoxiong Wu, Chen Lin, Huan Shan, Xiaojun Wu, Jin Zhao, Aidi Zhao, and Bing Wang 

Institutes 

  1. Yahui Mao – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

  2. Xiaochuan Ma – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

  3. Daoxiong Wu – CAS Key Laboratory of Materials for Energy Conservation, CAS Center for Excellence in Nanoscience, and Department of Material Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China 

  4. Chen Lin – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

  5. Huan Shan – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

  6. Xiaojun Wu – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China; CAS Key Laboratory of Materials for Energy Conservation, CAS Center for Excellence in Nanoscience, and Department of Material Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China 

  7. Jin Zhao – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China; ICQD and CAS Key Laboratory of Strongly-Coupled Quantum Matter Physics, and Department of Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

  8. Aidi Zhao – School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China; Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

Email: zhaoad@shanghaitech.edu.cn 

  1. Bing Wang – Hefei National Laboratory for Physical Sciences at the Microscale and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, Anhui 230026, China 

Email: bwang@ustc.edu.cn