Kavli Affiliate: Darrell G. Schlom
| First 5 Authors: , , , ,
| Summary:
The search for thin film electro-optic (EO) materials that can retain
superior performance under cryogenic conditions has become critical for quantum
computing. Barium titanate thin films show large linear EO coefficients in the
tetragonal phase at room temperature, which is severely degraded down to ~200
pm V$^-1$ in the rhombohedral phase at cryogenic temperatures. There is
immense interest in manipulating these phase transformations and retaining
superior EO properties down to liquid helium temperature. Utilizing the
thermodynamic theory of optical properties, a large low-temperature EO response
is designed by engineering the energetic competition between different
ferroelectric phases, leading to a low-symmetry monoclinic phase with a massive
EO response. The existence of this phase is demonstrated in a strain-tuned
BaTiO$_3$ thin film that exhibits a linear EO coefficient of 2516 +/- 100 pm
V$^-1$ at 5 K, which is an order of magnitude higher than the best reported
performance thus far. Importantly, the EO coefficient increases by 100x during
cooling, unlike the conventional films, where it degrades. Further, at the
lowest temperature, significant higher order EO responses also emerge. These
results represent a new framework for designing materials with property
enhancements by stabilizing highly tunable metastable phases with strain.
Copyright 2025 The Author(s). Advanced Materials published by Wiley-VCH GmbH.
This is an open access article under the terms of the Creative Commons
Attribution License, which permits use, distribution and reproduction in any
medium, provided the original work is properly cited. (A. Suceava, S. Hazra, A.
Ross, et al. "Colossal Cryogenic Electro-Optic Response Through Metastability
in Strained BaTiO3 Thin Films." Adv. Mater. (2025): e07564.
https://doi.org/10.1002/adma.202507564)
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