title: Unusual lattice vibration characteristics in whiskers of the pseudo-one-dimensional titanium trisulfide TiS3.
abstract: Transition metal trichalcogenides form a class of layered materials with strong in-plane anisotropy. For example, titanium trisulfide (TiS3) whiskers are made out of weakly interacting TiS3layers, where each layer is made of weakly interacting quasi-one-dimensional chains extending along the b axis. Here we establish the unusual vibrational properties of TiS3both experimentally and theoretically. Unlike other two-dimensional systems, the Raman active peaks of TiS3have only out-of-plane vibrational modes, and interestingly some of these vibrations involve unique rigid-chain vibrations and S-S molecular oscillations. High-pressure Raman studies further reveal that the AgS-SS-S molecular mode has an unconventional negative pressure dependence, whereas other peaks stiffen as anticipated. Various vibrational modes are doubly degenerate at ambient pressure, but the degeneracy is lifted at high pressures. These results establish the unusual vibrational properties of TiS3with strong in-plane anisotropy, and may have relevance to understanding of vibrational properties in other anisotropic two-dimensional material systems.
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Kedi
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Physics, University of Antwerp, Groenenborgerlaan 171, Antwerpen B-2020, Belgium.
authors.forename: Engin
authors.initials: E
authors.lastname: Torun
authors.affiliation: Department of Physics, University of Antwerp, Groenenborgerlaan 171, Antwerpen B-2020, Belgium.|Department of Photonics, Izmir Institute of Technology, Izmir 35430, Turkey.
authors.forename: Hasan
authors.identifier: http://orcid.org/0000-0002-6189-6707
authors.initials: H
authors.lastname: Sahin
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Chen
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Xi
authors.initials: X
authors.lastname: Fan
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Anupum
authors.initials: A
authors.lastname: Pant
authors.affiliation: LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: David
authors.initials: D
authors.lastname: Parsons Wright
authors.affiliation: LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Aoki
authors.affiliation: Department of Physics, University of Antwerp, Groenenborgerlaan 171, Antwerpen B-2020, Belgium.
authors.forename: Francois M
authors.initials: FM
authors.lastname: Peeters
authors.affiliation: LeRoy Eyring Center for Solid State Science, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Soignard
authors.affiliation: School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287, USA.
authors.forename: Sefaattin
authors.initials: S
authors.lastname: Tongay