Optical Signature of Moiré Superlattices Formed by Twisted SrTiO3 Membranes
Abstract
Moiré superlattices formed at the interfaces of mismatched lattices have attracted significant interest over the past decade due to their large tunability of band parameters and interactions among electrons, spins, and lattices. Superlattices made from twisted perovskite oxides may have strong structure and potential modulation, but evidence of such modulation over macroscopic areas, particularly at large twisting angles, has not been clearly demonstrated so far. Here, we fabricated millimeter-scale twisted oxide bilayers at 36∘ angle, close to the simple coincidence site lattice condition Σ5, from freestanding SrTiO3 membranes. We discovered new low-frequency vibrational modes whose Raman activity, according to molecular dynamics simulations, is greatly enhanced by an asymmetric, twisted interface between the SrO and TiO2 layers. Such an interface is energetically favorable from first-principles calculations and is corroborated by the observation of strong second harmonic generation from the interface comparable to that from the SrTiO3 surface throughout the bilayer region. The results are consistent with interlayer coupling enhanced by high-temperature annealing and confirmed by cross-sectional scanning transmission electron microscopy imaging. Our work sheds light on the structural behavior of twisted oxides and provides directions for tuning their phononic and nonlinear optical properties in future studies.
Versions
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BibTeX
@misc{shahriar2026optical,
title = {{Optical Signature of Moiré Superlattices Formed by Twisted SrTiO$_3$ Membranes}},
author = {T. A. M. Ragib Shahriar and Fumikazu Murakami and Xing He and Konnor Koons and Xinyan Li and Bumseop Kim and Shihan Qin and Varun Harbola and Jochen Mannhart and Yimo Han and Ruijuan Xu and Shengxi Huang and Andrew Rappe and Hanyu Zhu},
howpublished = {arXiv},
year = {2026},
month = jun,
doi = {10.48550/arxiv.2606.06289},
eprint = {2606.06289},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2606.06289},
note = {CC BY-NC-ND 4.0},
}
RIS
TY - UNPB
TI - Optical Signature of Moiré Superlattices Formed by Twisted SrTiO_3 Membranes
AU - T. A. M. Ragib Shahriar
AU - Fumikazu Murakami
AU - Xing He
AU - Konnor Koons
AU - Xinyan Li
AU - Bumseop Kim
AU - Shihan Qin
AU - Varun Harbola
AU - Jochen Mannhart
AU - Yimo Han
AU - Ruijuan Xu
AU - Shengxi Huang
AU - Andrew Rappe
AU - Hanyu Zhu
PY - 2026
DA - 2026/06/04
PB - arXiv
DO - 10.48550/arxiv.2606.06289
UR - https://arxiv.org/abs/2606.06289
AB - Moiré superlattices formed at the interfaces of mismatched lattices have attracted significant interest over the past decade due to their large tunability of band parameters and interactions among electrons, spins, and lattices. Superlattices made from twisted perovskite oxides may have strong structure and potential modulation, but evidence of such modulation over macroscopic areas, particularly at large twisting angles, has not been clearly demonstrated so far. Here, we fabricated millimeter-scale twisted oxide bilayers at 36^∘ angle, close to the simple coincidence site lattice condition Σ5, from freestanding SrTiO_3 membranes. We discovered new low-frequency vibrational modes whose Raman activity, according to molecular dynamics simulations, is greatly enhanced by an asymmetric, twisted interface between the SrO and TiO_2 layers. Such an interface is energetically favorable from first-principles calculations and is corroborated by the observation of strong second harmonic generation from the interface comparable to that from the SrTiO_3 surface throughout the bilayer region. The results are consistent with interlayer coupling enhanced by high-temperature annealing and confirmed by cross-sectional scanning transmission electron microscopy imaging. Our work sheds light on the structural behavior of twisted oxides and provides directions for tuning their phononic and nonlinear optical properties in future studies.
ER -