Manipulating anisotropy in 2D ferroelectric materials
Invited-In-person · Invited · Withdrawn
Abstract
2D ferroelectric materials are bringing us new opportunities in controlling material response to external stimuli and enabling novel device applications. The MX (M= Sn, Ge; X=S, Se) material family offers a unique combination of both 2D ferroelectricity and strong in-plane anisotropy, enabling a number of unique electrical, optical, thermal and mechanical properties. Here I would like to share some of our recent discoveries about this unique family of materials.
We have realized direct growth of 2D SnSe layers with AA stacking, which preserves the broken inversion symmetry of the monolayer crystals, leading to strong ferroelectric responses. The co-existence of in-plane and out-of-plane polarizations in different thicknesses of SnSe sheets is observed. More interestingly, these two polarizations are strongly correlated, enabling novel applications such as the dynamic tuning of in-plane optical second harmonic generation via controlling the out-of-plane electric field.
The strong in-plane anisotropy of the MX materials, such as SnS, also leads to novel energy valleys with selection rules that are fundamentally different from conventional valleytronic materials where cryogenic temperatures, strong electric or magnetic field are needed to differentiate the valleys. I will talk about our experimental demonstration of the valley effect in an ambient, and bias-free model system of SnS. We elucidate the direct access and identification of different sets of valleys, based on the selectivity in absorption and emission of linearly polarized light, and demonstrate strong optical dichroic anisotropy of up to 600% and nominal polarization degrees of up to 96%.
Another intriguing consequence of the in-plane anisotropy of MX materials is the unique ferroelectric responses with four ground states. We demonstrate that by leveraging the ultrafast and low-power crystallographic direction change of the MX material such as SnSe, the optical polarization state of the input signal can be tuned. This enables the implementation of next-generation high-speed polarization-encodable photonic memory cells for future photonic computing systems. Compared to the conventional PCMs, MX-based photonic memory offers ultrafast switching and low-optical-loss operations.
We have realized direct growth of 2D SnSe layers with AA stacking, which preserves the broken inversion symmetry of the monolayer crystals, leading to strong ferroelectric responses. The co-existence of in-plane and out-of-plane polarizations in different thicknesses of SnSe sheets is observed. More interestingly, these two polarizations are strongly correlated, enabling novel applications such as the dynamic tuning of in-plane optical second harmonic generation via controlling the out-of-plane electric field.
The strong in-plane anisotropy of the MX materials, such as SnS, also leads to novel energy valleys with selection rules that are fundamentally different from conventional valleytronic materials where cryogenic temperatures, strong electric or magnetic field are needed to differentiate the valleys. I will talk about our experimental demonstration of the valley effect in an ambient, and bias-free model system of SnS. We elucidate the direct access and identification of different sets of valleys, based on the selectivity in absorption and emission of linearly polarized light, and demonstrate strong optical dichroic anisotropy of up to 600% and nominal polarization degrees of up to 96%.
Another intriguing consequence of the in-plane anisotropy of MX materials is the unique ferroelectric responses with four ground states. We demonstrate that by leveraging the ultrafast and low-power crystallographic direction change of the MX material such as SnSe, the optical polarization state of the input signal can be tuned. This enables the implementation of next-generation high-speed polarization-encodable photonic memory cells for future photonic computing systems. Compared to the conventional PCMs, MX-based photonic memory offers ultrafast switching and low-optical-loss operations.
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Presenters
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Jie Yao
- UC Berkeley