Bulletin of the American Physical Society
APS March Meeting 2018
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session S08: Transport, Optical, and Thermodynamic Phenomena
11:15 AM–2:15 PM,
Thursday, March 8, 2018
LACC Room: 153C
Sponsoring Unit: DCMP
Chair: Heng Guo, UESTC China
Abstract: S08.00011 : Optical phonons in layer crystal of As2S3: effect of weak interlayer interaction.
1:15 PM–1:27 PM
(Physics, John Hopkins University)
As2S3 is known as layer crystal with structure which is very similar to the metal chalcogenides as MoS2 and some other. In such crystalline structure, the molecular unit is indefinitely extended in two dimensions. Center-zone optical phonons in 2D layer crystal As2S3 have been investigated in Raman scattering in temperature range of 4K-300K for both polarizations in the layer plane. Analysis of the symmetry of the crystal and 2D symmetry of the individual layer reveals that two symmetries predict different selection rules for optical phonons. Because crystal unit cell contains two layers, there are two times more (60) normal mode for the crystal compare to the layer (30). In the vanishing interaction between the layers, 60 modes collapse to 30 degenerated doublets. Weak interlayer interaction lifts these degeneracies with results of closely spaced doublets. Our experimental data show strong polarization dependence of Raman bands in ac plane at 134.4, 152.3, 185.5, 290.0, 309.4 and triplet 351.8, 354.1, 356.9 cm-1. The important evidence for the dominance of layer symmetry, along with very weak interaction between the layers, provides understanding of structural motives of As2S3 and may predict optical/electronic properties of similar 2D materials.
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