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Local strain engineering in atomically thin MoS2 and black phosphorus

Rafael Roldán

Orsay, pièce 355 aile Sud

Controlling the bandgap through local-strain engineering is an exciting avenue for tailoring optoelectronic materials. Two-dimensional crystals are particularly suited for this purpose because they can withstand unprecedented non-homogeneous deformations before rupture : one can literally bend them and fold them up almost like a piece of paper. In this talk, I will discuss our recent results on multi-layer MoS2 and black phosphorus sheets subjected to periodic stress, that allows to modulate their optoelectronic properties [1,2]. The experimental measurements show a remarkable shift of the optical absorption band-edge, which in the case of black phosphorus can be of up to 1 eV between the regions under tensile and compressive stress. To understand these results, we generalize a proper tight-binding model for MoS2 [3] and black phosphorus [4] under non-uniform conditions, accounting for the local modulation of the hopping integrals. Our results suggest, for the case of black phosphorus, that periodic stress modulation can yield to quantum confinement of carriers. The possibility of generating large strain-induced variations in the local density of charge carriers opens the door for a variety of applications including photovoltaics and two-dimensional optoelectronic devices.

[1] A. Castellanos-Gomez, R. Roldán, E. Cappelluti, M. Buscema, F. Guinea, H. SJ van der Zant and G. A. Steele. Nano Letters 13, 5361 (2013)
[2] J. Quereda, V. Parente, P. San-José, N. Agraït, G. Rubio-Bollinger, F. Guinea, R. Roldán and A. Castellanos-Gomez. arXiv : 1509.01182
[3] E. Cappelluti, R. Roldán, J.A. Silva-Guillén, P. Ordejón and F. Guinea. Phys. Rev. B 80, 085408 (2013).
[4] A. N. Rudenko and M. I. Katsnelson. Phys. Rev. B 89, 201408 (2014).

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