Flexible ultrafast spintronic terahertz emitter with exceptional working temperature range

Public summary

* An unprecedentedly wide working temperature range for ultrafast terahertz emitters (TEs) is achieved.

* The first all-inorganic soft ultrafast TE is achieved.

* A curved NiFe/SrRuO3/SrTiO3/mica heterostructure is fabricated as an ultrafast spintronic THz emitter.

Abstract

Spintronic terahertz (THz) emitters (TEs) leverage the spin degree of freedom. To address the growing demand for flexible TEs, we demonstrate a soft spintronic ultrafast TE based on a NiFe/SrRuO3/SrTiO3/mica(substrate) heterostructure. It emits picosecond 0–4 THz waves under near-infrared laser excitation, driven by the inverse spin Hall effect. Bendable samples with largely tunable curvatures (−2 cm−1≤ κ ≤ 2 cm−1) are achieved, by which a maximum 82% enhancement in the THz field strength is observed. We attribute it to tensile strain-induced large spin-orbit torque in SrRuO3. Significantly, we demonstrate an 80–500 K working temperature range for this all-inorganic flexible device, enabling applications under unprecedented extreme conditions (e.g., on the Moon’s surface or at the poles). Our work ushers in the dawn of extreme-temperature-environment, all-inorganic, wearable, and broadband ultrafast THz devices, which uncovers an unexplored area for the application of ultrafast THz photonics.