[Paper Review] Strong many-body interactions in ultrathin anisotropic tin (II) monosulfide

Abdus Salam Sarkar, Aamir Mushtaq+2 more|arXiv (Cornell University)|Nov 1, 2018

2D Materials and Applications64 references18 citations

TL;DR

This study demonstrates strong many-body interactions in ultrathin, anisotropic tin(II) monosulfide (SnS) synthesized via liquid phase exfoliation. Using temperature-dependent Raman spectroscopy, Z-scan, and ultrafast spectroscopy, the authors reveal linear phonon shifts, enhanced electron-phonon coupling, and significant exciton-exciton and coherent exciton-photon interactions, leading to strong nonlinear optical responses, positioning ultrathin SnS as a promising material for advanced thermoelectric and photonic devices.

ABSTRACT

Two-dimensional (2D) tin(II) monosulfide (SnS) with strong structural anisotropy has been proven to be a phosphorene analogue. However, difficulty in isolating very thin layer of SnS pose challenges in practical utilization. Here, we prepare ultrathin SnS via liquid phase exfoliation. With transmission electron microscopy, we identify the buckled structure of 2D SnS. We employ temperature dependent Raman spectroscopy to elucidate electron-phonon interactions, which reveals a linear phonon shifts. The active Raman modes of ultrathin SnS exhibit higher sensitivity to temperature than other 2D materials. Moreover, we demonstrate strong light-matter interaction in ultrathin SnS using Z-scan and ultrafast spectroscopy. Rich exciton-exciton and coherent exciton-photon interactions arising from many-particle excited effects in ultrathin SnS eventually enhances the nonlinear optical properties. Our findings highlight the prospects for the synthesis of ultrathin anisotropic SnS towards the betterment of thermoelectric and photonic devices.

Motivation & Objective

• To overcome challenges in isolating ultrathin SnS layers for practical applications.
• To investigate the electronic and vibrational properties of ultrathin SnS with strong structural anisotropy.
• To explore light-matter interactions and many-body effects in 2D SnS for enhanced nonlinear optical properties.
• To establish ultrathin SnS as a viable alternative to phosphorene in optoelectronic and thermoelectric applications.

Proposed method

• Ultrathin SnS was synthesized via liquid phase exfoliation to achieve few-layer structures.
• Transmission electron microscopy was used to confirm the buckled, anisotropic crystal structure of 2D SnS.
• Temperature-dependent Raman spectroscopy was employed to analyze electron-phonon coupling and phonon behavior.
• Z-scan technique was applied to measure nonlinear optical absorption and refraction.
• Ultrafast spectroscopy was used to probe coherent exciton-photon and exciton-exciton interactions.
• Theoretical analysis of Raman mode shifts and temperature sensitivity was performed to interpret experimental data.

Experimental results

Research questions

• RQ1 How do electron-phonon interactions manifest in ultrathin, anisotropic SnS at varying temperatures?
• RQ2 What is the role of many-body effects in enhancing nonlinear optical properties in 2D SnS?
• RQ3 How does the temperature-dependent Raman response of ultrathin SnS compare to other 2D materials?
• RQ4 To what extent do exciton-exciton and exciton-photon interactions contribute to the observed nonlinear optical response?
• RQ5 Can ultrathin SnS be effectively synthesized and characterized for use in photonic and thermoelectric devices?

Key findings

• Ultrathin SnS exhibits linear phonon frequency shifts with temperature, indicating strong electron-phonon coupling.
• Active Raman modes in ultrathin SnS show higher temperature sensitivity than in other 2D materials.
• Z-scan measurements confirm strong nonlinear optical absorption and refraction due to enhanced many-body interactions.
• Ultrafast spectroscopy reveals rich exciton-exciton and coherent exciton-photon interactions in ultrathin SnS.
• The material displays significantly enhanced nonlinear optical properties arising from many-particle excited-state effects.
• The buckled structure of 2D SnS was experimentally confirmed via transmission electron microscopy.