Ultrafast Photo‐Thermal Switching of Terahertz Spin Currents

Abstract

Dissipationless and scattering‐free spin‐based terahertz electronics is the futuristic technology for energy‐efficient information processing. Femtosecond light pulse provides an ideal pathway for exciting the ferromagnet (FM) out‐of‐equilibrium, causing ultrafast demagnetization and superdiffusive spin transport at sub‐picosecond timescale, giving rise to transient terahertz radiation. Concomitantly, light pulses also deposit thermal energy at short timescales, suggesting the possibility of abrupt change in magnetic anisotropy of the FM that could cause ultrafast photo‐thermal switching (PTS) of terahertz spin currents. Here, a single light pulse induced PTS of the terahertz spin current manifested through the phase reversal of the emitted terahertz photons is demonstrated. The switching of the transient spin current is due to the reversal of the magnetization state across the energy barrier of the FM layer. This demonstration opens a new paradigm for on‐chip spintronic devices enabling ultralow‐power hybrid electronics and photonics fueled by the interplay of charge, spin, thermal, and optical signals.

Reconfigurable terahertz metamaterials: From fundamental principles to advanced 6G applications

“…In conclusion, with the rapid development of critical science and technology in recent years, metamaterial-based THz photonics have been developed toward a standard and robust platform to achieve basic tunability for more functional applications. On the one hand, higher tunability, faster response rate, and lower power consumption are the challenges that remain for more commercial applications ( Li et al., 2020a ) ( Manjappa and Singh, 2020 ; Agarwal et al., 2021 ; Dong et al., 2021 ; Pitchappa et al., 2021b ). On the other hand, systematical work that required high integration and feasible software platform is also current blocks to be overcome ( Wu et al., 2019 ; Wan et al., 2021 ).…”

Large interfacial contribution to ultrafast THz emission by inverse spin Hall effect in CoFeB/Ta heterostructure

“…In recent years, THz emission time-domain spectroscopy has become another more promising technique for these measurements in a non-destructive and contactless manner ( Cheng et al., 2019 , 2021 ; Matthiesen et al., 2020 ). Either the spin-to-charge conversion in spintronic structures is directly seen in terms of the THz emission efficiency or THz pulses can be employed in time-domain spectroscopy to characterize them ( Agarwal et al., 2021 ). For example, temperature-dependent THz emission studies were used to determine the dominant intrinsic contribution to the spin-charge conversion mechanism in Co/Pt bilayer heterostructure ( Matthiesen et al., 2020 ).…”

THz emission from Fe/Pt spintronic emitters with L10-FePt alloyed interface

“…The THz emission from these spintronic THz emitters (STE) has remarkable properties in terms of signal strength and bandwidth; they are easy to use, robust, and do not require electrical connections. Their potential for technological applications is large, while the rich physics behind the excitation and emission has attracted scientific attention ( Agarwal et al., 2021 ; Hawecker et al., 2021 ; Zhang et al., 2020 ; Hoppe et al., 2021 ). During the last years, THz spintronic emitters have been heavily investigated aiming to obtain large signals and spectral bandwidths and to incorporate them into THz applications ( Papaioannou and Beigang, 2021 ; Bull et al., 2021 ; Wu et al., 2021 ).…”