DQMP Forum - Vivienne Chih-Ying Hsu - Tancredi Thai Angeloni

15.04.2025 13:00 – 14:00

Investigations on perovskite thin films and membranes using aberration corrected STEM
Vivienne Chih-Ying Hsu (group of prof. Triscone and prof. Caviglia)

Transition metal perovskite oxides illustrate strong correlations between atomic structure and functional properties [1].
When deposited as thin films, this enables manipulation of their electronic or magnetic properties by tuning their composition or strain state. On the other hand, perovskite membrane has come into interest for its different advantages, i.e. no structural mismatch, possibilities to create texture (wrinkels), stacking, and eventually down scaling towards 2D materials,etc [2].
To understand these different correlations and different possibilities, aberration corrected scanning transmission electron microscopy (Cs-STEM) has become an important tool to measure the deposited lattices and transferred membranes, not only to resolve and identify atomic columns, but also to characterize the local electronic states and chemical compositions.
[1] Ngai, J.H. et al. Annu. Rev. Mater. Res. 44 (2014) 1–17.
[2] A. J. Yang et al., ACS Nano. 17, 9748–9762 (2023).

Excitation of surface phonon polaritons in the far field
Tancredi Thai Angeloni (group of prof. Caviglia)

Non-linear interactions between phonons have
been sucessfullly used to induce transient lattice distoritions and phase transitions [1]. In this context, the engineering and manipulation
of the light-phonon interactions opens up new possibilities for non-linear phononics. Through taylored gold microstructures it is indeed possible to excite and manipulate surface phonon modes, known as surface phonon polaritons(SPhP). These modes show a mixture of longitudinal and transverse polarization and reside in the Resthralen band, the frequency interval where no direct coupling of phonons and radiation is allowed. A systematic engineering of the gold gratings on top of lanthanum aluminate is done to study the dispersion relation and access the SPhP modes in the far field. Lanthanum aluminate is known to have non-linear phononics processes [2], picturing an interesting perspective on further study of its surface phonon modes.
[1] Disa, A.S., Nova, T.F. Cavalleri, A., “Engineering crystal structures with light”, Nat. Phys. 17, 1087–1092 (2021).
[2] Hortensius, J.R., Afanasiev, D., Sasani, A. et al., “Ultrafast strain engineering and coherent structural dynamics from resonantly driven optical phonons in LaAlO3”, NPJ Quantum
Mater. 5, 95 (2020).

Lieu

Bâtiment: Ecole de Physique

Auditoire Stückelberg

entrée libre