Work

Identifying Degenerate Shear and Layer Breathing Modes in Few‐Layer 1T‐PtS 2 by Circularly Polarized Raman Spectroscopy

Year: 2026

Type: article

Abstract: ABSTRACT Quasi‐covalent interlayer bonding in 1T‐PtS 2 gives rise to pronounced thickness‐dependent optical and electronic properties, yet its impact on vibrational properties remains poorly understood. In particular, low‐frequency interlayer vibrations probe directional restoring forces, but the shear and breathing components have not been independently identified in 1T‐PtS 2 . In this work, nearly degenerate in‐plane shear modes and out‐of‐plane layer‐breathing modes in few‐layer 1T‐PtS 2 are resolved using circularly polarized Raman spectroscopy. Helicity selection rules separate E‐symmetry in‐plane vibrations from A‐symmetry out‐of‐plane vibrations, enabling independent extraction of shear and breathing force constants with a linear chain model. The extracted values are nearly identical, in sharp contrast to conventional van der Waals layered materials, where the breathing response is typically much stiffer than the shear response. The same helicity‐resolved spectra further clarify the Davydov splitting of high‐frequency intralayer modes and reveal additional E‐symmetry features tentatively assigned to second‐order combination modes. These findings show that strong interlayer bonding in 1T‐PtS 2 underlies a nearly isotropic interlayer force landscape, providing a vibrational basis for its thickness‐tunable optoelectronic and phononic functionality.

Source: Small

DOI: 10.1002/smll.76236

Authors: Byeong Wook Cho, Jina Lee, Duhee Yoon, Young Hee Lee

Institutions: Institute for Basic Science, Sungkyunkwan University, Peking University, Hubei University of Technology

Language: English

Topic: 2D Materials and Applications

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: bronze

Funder: Institute for Basic Science

Awards: G1330615973, G258299307