Rhombohedral(R)-stacked TMD means the neighbouring layers are oriented in the same direction, which can be obtained through either chemical synthesis or artificial stack with a small twist. The investigation into how the stacking order determines the properties of TMD homobilayers is crucial for understanding the exotic physics observed in two-dimensional semiconductors.
Here we use various optical spectroscopy techniques to explore the emergent excitonic and correlated phenomena in both homogeneous and twisted TMD homobilayers of rhombohedral stacking. Specifically, we observe a spontaneous electrical polarization arising from the asymmetric interlayer-coupling-induced Berry phase in R-stacked MoS2 bilayer. Utilizing this polarization, we achieve an efficient and scalable photovoltaic effect in a Gr/R-MoS2/Gr heterostructure. By employing non-degenerate pump-probe photocurrent spectroscopy, we disentangle the competition between thermal and electronic effects, extracting a 2ps intrinsic photocurrent speed.
More importantly, the out-of-plane electrical polarization in R-stacked MoS2 can be switched through in-plane sliding motion, which is referred to as sliding ferroelectricity. By harnessing the coupling between electronic polarization and excitonic effects, we demonstrate an optical method to probe the domain wall motion in both R-stacked MoS2 homo-bilayer and tri-layer.
Finally, we report the discovery of a series of correlated insulating states at both integer and fractional fillings, arising from Γ-valley flat bands, in a small-angle twisted MoSe2 homo-bilayer. We observe a Mott-insulator state instead of a semi-metal on the half-filled honeycomb lattice, in contrast to the theoretical prediction based on continuum model. The observed phenomenon is consistent with the picture of semi-metal to insulator transition at large U/t limit. Our exploration on the moire homo-bilayer in rhombohedral stacking offers a new opportunity to simulate the Mott-Hubbard physics with spin SU (2) symmetry.
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2024-05-01T12:00:002024-05-01T14:00:00Emergent optical and electronic properties in atomically thin rhombohedral-stacked transition metal dichalcogenidesEvent Information:
Abstract:
Rhombohedral(R)-stacked TMD means the neighbouring layers are oriented in the same direction, which can be obtained through either chemical synthesis or artificial stack with a small twist. The investigation into how the stacking order determines the properties of TMD homobilayers is crucial for understanding the exotic physics observed in two-dimensional semiconductors.
Here we use various optical spectroscopy techniques to explore the emergent excitonic and correlated phenomena in both homogeneous and twisted TMD homobilayers of rhombohedral stacking. Specifically, we observe a spontaneous electrical polarization arising from the asymmetric interlayer-coupling-induced Berry phase in R-stacked MoS2 bilayer. Utilizing this polarization, we achieve an efficient and scalable photovoltaic effect in a Gr/R-MoS2/Gr heterostructure. By employing non-degenerate pump-probe photocurrent spectroscopy, we disentangle the competition between thermal and electronic effects, extracting a 2ps intrinsic photocurrent speed.
More importantly, the out-of-plane electrical polarization in R-stacked MoS2 can be switched through in-plane sliding motion, which is referred to as sliding ferroelectricity. By harnessing the coupling between electronic polarization and excitonic effects, we demonstrate an optical method to probe the domain wall motion in both R-stacked MoS2 homo-bilayer and tri-layer.
Finally, we report the discovery of a series of correlated insulating states at both integer and fractional fillings, arising from Γ-valley flat bands, in a small-angle twisted MoSe2 homo-bilayer. We observe a Mott-insulator state instead of a semi-metal on the half-filled honeycomb lattice, in contrast to the theoretical prediction based on continuum model. The observed phenomenon is consistent with the picture of semi-metal to insulator transition at large U/t limit. Our exploration on the moire homo-bilayer in rhombohedral stacking offers a new opportunity to simulate the Mott-Hubbard physics with spin SU (2) symmetry.Event Location:
QMI 188 (2355 East Mall)