Anomalous interlayer vibrations in strongly coupled layered PdSe2

Alexander A. Puretzky; Akinola D. Oyedele; Kai Xiao; Amanda V. Haglund; Bobby G. Sumpter; David Mandrus; David B. Geohegan; Liangbo Liang

doi:10.1088/2053-1583/aabe4d

Anomalous interlayer vibrations in strongly coupled layered PdSe₂

Alexander A. Puretzky, Akinola D. Oyedele, Kai Xiao, Amanda V. Haglund, Bobby G. Sumpter, David Mandrus, David B. Geohegan, Liangbo Liang

Research output: Contribution to journal › Article › peer-review

65 Scopus citations

Abstract

In this work, we show unusual effects of strong interlayer coupling on low-frequency (LF) Raman scattering in exfoliated PdSe₂ crystals with different number of layers. Unlike many other layered materials, it is found that the measured frequencies of the breathing modes cannot be simply described by a conventional linear chain model (LCM) that treats each layer as a single rigid object. By using first-principles calculations, we show that strong deviations from layer rigidity can occur for the LF breathing vibrations of PdSe₂, which accounts for the observed disagreement with the conventional LCM. The layer non-rigidity and strong interlayer coupling could also explain the unusual strong intensities of the LF breathing modes that are comparable with those of the high-frequency Raman modes. These strong intensities allowed us to use a set of the measured LF Raman lines as unique fingerprints for a precise assignment of the layer numbers. The assignment of the layer numbers was further confirmed using second harmonic generation that appeared only in the noncentrosymmetric even-layer PdSe₂ crystals. This work thus demonstrates a simple and fast approach for the determination of the number of layers in 2D materials with strong interlayer coupling and non-rigid interlayer vibrations.

Original language	English
Article number	035016
Journal	2D Materials
Volume	5
Issue number	3
DOIs	https://doi.org/10.1088/2053-1583/aabe4d
State	Published - May 4 2018

Funding

This research was conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. LL was also supported by a Eugene P Wigner Fellowship at Oak Ridge National Laboratory.DM and AVH acknowledge support from the National Science Foundation under Grant No. NSF DMR-1410428. This research was conducted at the Center for Nanophase Materials Sciences (CNMS), which is a DOE Office of Science User Facility. LL was also supported by a Eugene P Wigner Fellowship at Oak Ridge National Laboratory. DM and AVH acknowledge support from the National Science Foundation under Grant No. NSF DMR-1410428. *Notice: This manuscript has been authored by UT-Battelle, LLC, under contract DE-AC05-00OR22725 with the US Department of Energy (DOE). The US government retains and the publisher, by accepting the article for publication, acknowledges that the US government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for US government purposes. DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).

Keywords

2D materials
PdSe
layer partial-rigidity
linear chain model
low-frequency Raman
strong interlayer coupling

Access to Document

10.1088/2053-1583/aabe4d

Cite this

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title = "Anomalous interlayer vibrations in strongly coupled layered PdSe2 ",

abstract = "In this work, we show unusual effects of strong interlayer coupling on low-frequency (LF) Raman scattering in exfoliated PdSe2 crystals with different number of layers. Unlike many other layered materials, it is found that the measured frequencies of the breathing modes cannot be simply described by a conventional linear chain model (LCM) that treats each layer as a single rigid object. By using first-principles calculations, we show that strong deviations from layer rigidity can occur for the LF breathing vibrations of PdSe2, which accounts for the observed disagreement with the conventional LCM. The layer non-rigidity and strong interlayer coupling could also explain the unusual strong intensities of the LF breathing modes that are comparable with those of the high-frequency Raman modes. These strong intensities allowed us to use a set of the measured LF Raman lines as unique fingerprints for a precise assignment of the layer numbers. The assignment of the layer numbers was further confirmed using second harmonic generation that appeared only in the noncentrosymmetric even-layer PdSe2 crystals. This work thus demonstrates a simple and fast approach for the determination of the number of layers in 2D materials with strong interlayer coupling and non-rigid interlayer vibrations.",

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author = "Puretzky, {Alexander A.} and Oyedele, {Akinola D.} and Kai Xiao and Haglund, {Amanda V.} and Sumpter, {Bobby G.} and David Mandrus and Geohegan, {David B.} and Liangbo Liang",

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AU - Haglund, Amanda V.

AU - Sumpter, Bobby G.

AU - Mandrus, David

AU - Geohegan, David B.

AU - Liang, Liangbo

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N2 - In this work, we show unusual effects of strong interlayer coupling on low-frequency (LF) Raman scattering in exfoliated PdSe2 crystals with different number of layers. Unlike many other layered materials, it is found that the measured frequencies of the breathing modes cannot be simply described by a conventional linear chain model (LCM) that treats each layer as a single rigid object. By using first-principles calculations, we show that strong deviations from layer rigidity can occur for the LF breathing vibrations of PdSe2, which accounts for the observed disagreement with the conventional LCM. The layer non-rigidity and strong interlayer coupling could also explain the unusual strong intensities of the LF breathing modes that are comparable with those of the high-frequency Raman modes. These strong intensities allowed us to use a set of the measured LF Raman lines as unique fingerprints for a precise assignment of the layer numbers. The assignment of the layer numbers was further confirmed using second harmonic generation that appeared only in the noncentrosymmetric even-layer PdSe2 crystals. This work thus demonstrates a simple and fast approach for the determination of the number of layers in 2D materials with strong interlayer coupling and non-rigid interlayer vibrations.

AB - In this work, we show unusual effects of strong interlayer coupling on low-frequency (LF) Raman scattering in exfoliated PdSe2 crystals with different number of layers. Unlike many other layered materials, it is found that the measured frequencies of the breathing modes cannot be simply described by a conventional linear chain model (LCM) that treats each layer as a single rigid object. By using first-principles calculations, we show that strong deviations from layer rigidity can occur for the LF breathing vibrations of PdSe2, which accounts for the observed disagreement with the conventional LCM. The layer non-rigidity and strong interlayer coupling could also explain the unusual strong intensities of the LF breathing modes that are comparable with those of the high-frequency Raman modes. These strong intensities allowed us to use a set of the measured LF Raman lines as unique fingerprints for a precise assignment of the layer numbers. The assignment of the layer numbers was further confirmed using second harmonic generation that appeared only in the noncentrosymmetric even-layer PdSe2 crystals. This work thus demonstrates a simple and fast approach for the determination of the number of layers in 2D materials with strong interlayer coupling and non-rigid interlayer vibrations.

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