Condensed Matter Seminar
Effects of non-uniform and uniaxial strain in transition-metal dichalcogenides
Dr. Moshe G. Harats
Department of Materials Engineering, Ben-Gurion University
Abstract
2D materials, and in particular transition-metal dichalcogenides (TMDs) are elastic materials that can sustain high strain. The effects of uniform (uniaxial) strain and non-uniform strain have been investigated in the last decade. In this talk I will present recent studies done in our lab which reveal new phenomena that were not observed (or at least not understood) with different strain engineering methods. In the first part I will present new results of the photoluminescence from uniaxially strained TMDs where we observe fluctuating intensities as a function of strain for low strain magnitudes (<0.2%). By combining k-space imaging with the strain, we find that both the choice of substrate and the curvature define the intensity of the emission [1].
In the second part we will present recent results that resolve a long-standing debate between funneling of excitons under non-uniform strain and exciton-to-trion conversion due to limited funneling [2]. We show that by suspending monolayers on top of large holes, and by choosing the right configuration of substrate, funneling can be reached for micron-size regions while avoiding exciton-to-trion conversion that was observed in previous works [3].
[1] L. Grimberg, S. Kostyukovets, N. Basu, and M. G. Harats, Angular Emission Properties of Strained Transition-Metal Dichalcogenides in the Low Strain Regime, ACS Appl. Mater. Interfaces 18, 29337 (2026).
[2] M. G. Harats and K. I. Bolotin, Limits of funneling efficiency in non-uniformly strained 2D semiconductors, 2d Mater. 8, 015010 (2021).
[3] M. G. Harats, J. N. Kirchhof, M. Qiao, K. Greben, and K. I. Bolotin, Dynamics and efficient conversion of excitons to trions in non-uniformly strained monolayer WS2, Nature Photonics 14, 324 (2020).
In the second part we will present recent results that resolve a long-standing debate between funneling of excitons under non-uniform strain and exciton-to-trion conversion due to limited funneling [2]. We show that by suspending monolayers on top of large holes, and by choosing the right configuration of substrate, funneling can be reached for micron-size regions while avoiding exciton-to-trion conversion that was observed in previous works [3].
[1] L. Grimberg, S. Kostyukovets, N. Basu, and M. G. Harats, Angular Emission Properties of Strained Transition-Metal Dichalcogenides in the Low Strain Regime, ACS Appl. Mater. Interfaces 18, 29337 (2026).
[2] M. G. Harats and K. I. Bolotin, Limits of funneling efficiency in non-uniformly strained 2D semiconductors, 2d Mater. 8, 015010 (2021).
[3] M. G. Harats, J. N. Kirchhof, M. Qiao, K. Greben, and K. I. Bolotin, Dynamics and efficient conversion of excitons to trions in non-uniformly strained monolayer WS2, Nature Photonics 14, 324 (2020).