We investigate the ultrafast photoinjection process initiated by a few-femtosecond optical pulse in monocrystalline undoped germanium with attosecond transient reflectivity spectroscopy. By comparison with theoretical calculations, we decouple several distinct but concurring physical phenomena that are found to exhibit different timing within the pump envelope. As a result of their complex interplay, we found that intra-band motion hinders charge injection, in contrast with what has previously been observed in other semiconductors.
Light fields can sculpt the optical and electronic properties of solids by injecting charge carriers from the valence to the conduction band. The photoinjection process typically unfolds on time scales shorter than the period of the driving radiation, thus being - for visible and near-infrared light - below one femtosecond. Despite being pervasive, only a few experiments investigated the photoinduced charge excitation produced by an intense, ultrashort laser pulse with attosecond temporal resolution. Here we used attosecond transient reflection spectroscopy in combination with a two-fold, advanced theoretical approach to demonstrate that there is not a single photoexcitation mechanism responsible for charge injection in germanium. Instead, it stems from multi-photon absorption and band dressing, while intra-band motion has a hindering effect.
Tuning the Dzyaloshinskii-Moriya interaction (DMI) using electric (E)-fields in magnetic devices has opened up new perspectives for controlling the stabilization of chiral spin structures. Recent efforts have used voltage-induced charge redistribution at magnetic/oxides interfaces to modulate the DMI. This approach is attractive for active devices but tends to be volatile, making it energy-demanding. Here we demonstrate nonvolatile E-field manipulation of the DMI by ionic-liquid gating of Pt/Co/HfO2 ultra thin films. The E-field effect on the DMI is linked to the migration of oxygen species from the HfO2 layer into the Co and Pt layers and subsequent anchoring. This effect permanently changes the properties of the material, showing that E-fields can be used not only for local gating in devices but also as a material design tool for post growth tuning of the DMI.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.