Nonlinear optical spectroscopy and imaging in 2D materials – Leandro Malard – FIS-UFMG

Data / Hora
Date(s) - 14/05/2020
17:00

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COLÓQUIO DO DEPARTAMENTO DE FÍSICA

Nonlinear optical spectroscopy and imaging in 2D materials

Leandro M. Malard

Departamento de Física
Universidade Federal de Minas Gerais

14/05 – 5a. f – 17h

In this work we will show our recent developments on the non-linear optical properties of novel
2D materials. We have used both Second Harmonic Generation (SHG) and Coherent Anti Stokes
Raman Scattering (CARS) to study mono- and few-layers of semiconducting dichalcogenides
and graphene respectively. In the case of the MoS2 we have observed efficient SHG from odd
number of layers due to the absence of inversion symmetry [1]. By using different laser
excitation energies, we could probe the resonant effect in the SHG in MoS2, MoSe2 and WS2. By
analyzing the resonant profile of SHG we can observe the different types of excitons in this
material, which are compared with recent theoretical results in the literature [2]. Because
graphene have inversion symmetry, the SHG is almost absent, however third order nonlinearities
are greatly enhanced in this material due its peculiar band structure. We will discuss the CARS
process in graphene and h-BN [3]. More recently we have also shown that SHG can be a useful
tool to identify and characterize grain boundaries and edges in different 2D materials [4].

[1] L. M. Malard et al., Phys. Rev. B 87, 201401 (2013).
[2] A. Corradi, in preparation.
[3] L. Lafetá, Nano Lett. 17, 3447 (2017).
[4] B. R. Carvalho, Nano Lett. in press (2020).