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approvedone_page.pdf2015-04-16 11:34:01Zhang Chendong

Abstracts

Author: Zhang Chendong
Requested Type: Oral
Submitted: 2015-04-14 12:12:34

Co-authors: Yuxuan Chen, Amber Johnson, Ming-Yang Li, Jing-Kai Huang, Lain-Jong Li and Chih-Kang Shih

Contact Info:
Depart. of Phys., UT Austin
2515 Speedway RLM. 5.208
Austin, TX-Texas   78731
United States

Abstract Text:
The recent optical measurements demonstrated the intriguing indirect-to-direct band gap transition of transition metal dichalcogenides (TMDs) at single layer (SL) thickness, while one important issue that remains unresolved is the quasiparticle band structure and the magnitude of the exciton binding energy. Compared with the previous optical spectroscopies and angle resolved photoemission investigations, the scanning tunneling spectroscopy (STS) has the unique advantages in probing the quasiparticle band structures of the TMD samples with a limited lateral size. However, the STS investigations thus far have not yield consistent results. Here with a comprehensive approach of STS, we map out, for first time, the critical point energy locations in both the valence and conduction bands of TMD compounds. The systematic trend of such energy locations is unraveled as a function of the TM-Chalcogene orbital coupling, the TM spin-orbital coupling, as well as the interlayer coupling. Combining with optical studies, this capability also allows us to address the issue of exciton binding energy with much less uncertainty. In addition, we apply this technique to investigate how the dielectric screening environment would renormalize the band structures. Such knowledge is critical for the flourishing field of TMDs as emerging atomically thin 2D electronic and photonic materials.

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