Reconfigurable Mie resonator metasurfaces may give rise to new classes of programmable optical devices. Large phase and amplitude modulations can be achieved with high-Q resonances that are tunable by at least one line-width. We experimentally demonstrate narrow linewidth, reconfigurable Mie resonators comprising undoped InSb wires embedded inside a highly doped InSb Epsilon-Near-Zero (ENZ) cavity. We demonstrate a Q-factor increase of 400% by embedding a high index resonator within, instead of atop, an ENZ substrate. Systematic studies of varying width resonators reveal significant differences in coupling to the ENZ media for TM and TE resonators. A large refractive index modulation (Δn ≥1.5) is achieved with heating (80-575K), stemming from variations in the effective mass of free-carriers. Thermally tuning the ENZ wavelength of the cavity by >2μm (13-15.5μm) emables reconfigurable tuning by multiple line-widths. This ultra-wide thermal tunability of high-Q embedded resonators may enable new class of active metadevices in the mid-infrared wavelength regime.
A distinguishing feature of spin accumulation in ferromagnet-semiconductor devices is its precession in a magnetic field. This is the basis for detection techniques such as the Hanle effect, but these approaches become ineffective as the spin lifetime in the semiconductor decreases. For this reason, no electrical Hanle measurement has been demonstrated in GaAs at room temperature. We show here that by forcing the magnetization in the ferromagnet to precess at resonance instead of relying only on the Larmor precession of the spin accumulation in the semiconductor, an electrically generated spin accumulation can be detected up to 300~K. The injection bias and temperature dependence of the measured spin signal agree with those obtained using traditional methods. We further show that this new approach enables a measurement of short spin lifetimes (< 100~psec), a regime that is not accessible in semiconductors using traditional Hanle techniques.
The measurements were carried out on epitaxial Heusler alloy (Co2FeSi or Co2MnSi)/n-GaAs heterostructures. Lateral spin valve devices were fabricated by electron beam and photolithography. We compare measurements carried out by the new FMR-based technique with traditional non-local and three-terminal Hanle measurements. A full model appropriate for the measurements will be introduced, and a broader discussion in the context of spin pumping experimenments will be included in the talk. The new technique provides a simple and powerful means for detecting spin accumulation at high temperatures.
Reference: C. Liu, S. J. Patel, T. A. Peterson, C. C. Geppert, K. D. Christie, C. J. Palmstrøm, and P. A. Crowell, “Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance,” Nature Communications 7, 10296 (2016). http://dx.doi.org/10.1038/ncomms10296
The recent rapid progress in the field of spintronics requires extensive studies of carrier and spin relaxation dynamics in
semiconductors. In this work, we employed time and spin resolved differential transmission measurements in order to
probe carrier and spin relaxation times in several InAsP ternary alloys. In addition, the dynamics of the excitonic
radiative transitions of InAs<sub>0.13</sub>P<sub>0.87</sub> epitaxial layer were studied through the time-resolved photoluminescence
Transition metal aluminides and gallides and rare earth monopnictides have been grown as buried conducting layers in
111-v compound semiconductor heterostructures. These metallic and semi-metallic compounds have the CsC1 and NaC1
structures, respectively. The criteria for achieving (100) oriented epitaxial growth on (100)111-V semiconductor surfaces are
different for each class of material. The methods used to achieve 111-V/metal/Ill-V heteroepitaxial structures are described. The
different approaches needed for the aluminides or gallides and the monopnictides form the basis for a comparative study.