arXiv subjects

Fernando Calle

Publications and source records attributed to Fernando Calle.

5 recordsLinked to original sources

arXiv2025

Moving magnetic domain walls with sound alone

Surface Acoustic Waves (SAW) have been used in spintronic applications to decrease the magnetic field or the electric current required to act on the magnetization. A common belief is that a SAW alone cannot achieve a directed magnetic switching in a device without an assisting magnetic field or electric current. In this work, we demonstrate magnetic domain wall motion driven solely by an acoustic wave. Using XMCD-PEEM, we show extensive evidence of SAW-induced and field-free magnetic domain wall motion (DW) in the direction of the wave propagation. Our micromagnetic simulations reveal a mechanism that allows the SAW to transfer linear momentum to the DW. Experimentally, the largest DW average velocity measured was ~12 m/s, although our simulations predict that velocities in the range of 100 m/s could be attained. This new mechanism opens the door to designing innovative spintronic devices where the magnetization can be controlled exclusively by an acoustic wave.

cond-mat.mes-hall↗

arXiv2020

Exciton-Plasmon Coupling in 2D Semiconductors by Surface Acoustic Waves

We theoretically demonstrate the coupling between excitons in 2D semiconductors and surface plasmons in a thin metal film by means of a surface acoustic wave (SAW), proving that the generated exciton-plasmon polaritons (or plexcitons) are in the strong coupling regime. The strain field of the SAW creates a dynamic diffraction grating providing the momentum match for the surface plasmons, whereas the piezoelectric field, that could dissociate the excitons, is cancelled out by the metal. This is exemplified for monolayer MoS$\mathrm{_{2}}$ and mono- and few-layer black phosphorus on top of a thin silver layer on a LiNbO$\mathrm{_{3}}$ piezoelectric substrate, providing Rabi splittings of 100-150 meV. Thus, we demonstrate that SAWs are powerful tools to modulate the optical properties of supported 2D semiconductors by means of the high-frequency localized deformations tailored by the acoustic transducers, that can serve as electrically switchable launchers of propagating plexcitons suitable for active high-speed nanophotonic applications.

cond-mat.mes-hall↗

arXiv2019

Dynamic local strain in graphene generated by surface acoustic waves

We experimentally demonstrate that the Raman active optical phonon modes of single layer graphene can be modulated by the dynamic local strain created by surface acoustic waves (SAWs). In particular, the dynamic strain field of the SAW is shown to induce a Raman scattering intensity variation as large as 15% and a phonon frequency shift of up to 10 cm$^{-1}$ for the G band, for instance, for an effective hydrostatic strain of 0.24% generated in a single layer graphene atop a LiNbO$_{3}$ piezoelectric substrate with a SAW resonator operating at a frequency of $ \sim $ 400 MHz. Thus, we demonstrate that SAWs are powerful tools to modulate the optical and vibrational properties of supported graphene by means of the high-frequency localized deformations tailored by the acoustic transducers, which can also be extended to other 2D systems.

cond-mat.mes-hall↗

arXiv2018

Impact of 2D-Graphene on SiN Passivated AlGaN/GaN MIS-HEMTs under Mist Exposure

The effect of a two dimensional (2D) graphene layer (GL) on top of the silicon nitride (SiN) passivation layer of AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) has been systematically analyzed. Results showed that in the devices without the GL, the maximum drain current density (I_D,max) and the maximum transconductance (g_m,max) decreased gradually as the mist exposure time increased, up to 23% and 10%, respectively. Moreover, the gate lag ratio (GLR) increased around 10% during mist exposure. In contrast, devices with a GL showed a robust behavior and not significant changes in the electrical characteristics in both DC and pulsed conditions. The origin of these behaviors has been discussed and the results pointed to the GL as the key factor for improving the moisture resistance of the SiN passivation layer.

physics.app-ph↗

arXiv2013

Coupling light into graphene plasmons through surface acoustic waves

We propose a scheme for coupling laser light into graphene plasmons with the help of electrically generated surface acoustic waves. The surface acoustic wave forms a diffraction grating which allows to excite the long lived phonon-like branch of the hybridized graphene plasmon-phonon dispersion with infrared laser light. Our approach avoids patterning the graphene sheet, does not rely on complicated optical near-field techniques, and allows to electrically switch the coupling between far field radiation and propagating graphene plasmons.

cond-mat.mes-hall↗