Ultrafast optical probes of dynamic behavior in La0.7Sr0.3MnO3/YBa2Cu3O7 − δ/La0.7Sr0.3MnO3 heterostructure

Surface Recombination in Ultra-Fast Carrier Dynamics of Perovskite Oxide La0.7Sr0.3MnO3 Thin Films

“…For comparison, first-principles calculations and TR experiments on the thicker LSMO films (bulk) reveal large spin-polarity in the optical transitions, occurring through O­(2 p ) → Mn­(3 d ) transition. While our results on the bulk LSMO films are consistent with previous reports, − excitation-density dependent TR on thinner LSMO films ( d < 20 nm) reveals a faster relaxation mechanism (τ ∼ 10 ps), which is attributed to the surface recombination. DFT calculations also indicate a significant enhancement in the surface density of states (DOS) with decreasing film thickness, yielding an additional surface relaxation mechanism in ultrathin films.…”

“…Previous studies on bulk LSMO films have identified electron–phonon relaxation (τ < 1 ps) and phonon-assisted spin–lattice relaxation (τ ∼ 10 ps) through the low-temperature-dependent transient-optical response. − However, there is limited information about this response in thin films near room temperature, which will be relevant for many future device applications and where differences in ultrafast dynamics due to surface and interface effects are expected. For example, by decreasing the film thickness, the surface to bulk ratio increases and the surface electrons dominate the features from the bulk electrons.…”