from first-principles

Recent development of intense ultrashort mid and far infrared laser sources has created an opportunity for functional materials based on direct excitation of infrared active phonons. Strong excitation of infrared active phonons can produce large unidirectional distortions of the crystal structure through special non-linear coupling^1-4. Complex oxides provide an important test-ground for this experimental approach due to their diversity, strong coupling to optical fields, and demonstrated connection between subtle structural changes and fundamental properties. Early experiments in complex oxides are intriguing - suggesting that this mechanism can transiently induce insulator-metal phase transitions¹ and enhance superconductivity². Hidden A-type antiferromagnetism (A-AFM) has been predicted in rare-earth titanates (between SmTiO₃ and GdTiO₃) but not found using static techniques like solid solution or strain. We show how optical excitation of infrared phonons gives dynamical access to the A-AFM phase in GdTiO₃ through Jahn-Teller and Gd distortions that are challenging to access with static techniques.

1) Forst, M. et al. Nat Phys 7, 854–856 (2011)
2) Mankowsky, R. et al. Nature 516, 71–73 (2014)
3) Subedi, A. PRB 92, 214303 (2015)
4) Juraschek, D. M. et al. PRL 118, 054101 (2017)