arXiv subjects

C. T. Harris

Publications and source records attributed to C. T. Harris.

3 recordsLinked to original sources

arXiv2026

Cryogenic enhancement of phononic four-wave mixing in AlScN/SiC

Surface acoustic wave platforms based on piezoelectric thin-film heterostructures provide sub-wavelength acoustic confinement, making them attractive for compact nonlinear phononic systems with applications including frequency conversion, parametric interactions, and nonlinear signal processing. Here, we investigate guided surface acoustic wave phononic four-wave mixing at gigahertz frequencies in an aluminum scandium nitride/4H-silicon carbide heterostructure operated at both room temperature (295 K) and cryogenic temperature (4 K). The 500 nm thick aluminum scandium nitride film supports guided Rayleigh and Sezawa modes with distinct displacement and strain energy density distributions, allowing a direct comparison of mode-dependent nonlinear behavior within the same device. Continuous-wave four-wave mixing measurements reveal an enhancement in the extracted modal nonlinear coefficient at 4 K relative to 295 K for both modes. In addition, the Rayleigh mode exhibits a modal nonlinearity approximately two orders of magnitude larger than that of the Sezawa mode across both temperature regimes. These results demonstrate that phononic four-wave mixing is strongly influenced by temperature, mode confinement, and strain localization while establishing aluminum scandium nitride on silicon carbide heterostructures as a promising platform for engineering enhanced nonlinear phononic interactions for future classical and quantum acoustic on-chip signal processing systems.

physics.app-ph↗

arXiv2021

Towards Deterministic Creation of Single Photon Sources in Diamond using In-Situ Ion Counting

We present an in-situ counted ion implantation experiment reducing the error on the ion number to 5 % enabling the fabrication of high-yield single photon emitter devices in wide bandgap semiconductors for quantum applications. Typical focused ion beam implantation relies on knowing the beam current and setting a pulse length of the ion pulse to define the number of ions implanted at each location, referred to as timed implantation in this paper. This process is dominated by Poisson statistics resulting in large errors for low number of implanted ions. Instead, we use in-situ detection to measure the number of ions arriving at the substrate resulting in a two-fold reduction in the error on the number of implanted ions used to generate a single optically active silicon vacancy (SiV) defect in diamond compared to timed implantation. Additionally, through post-implantation analysis, we can further reduce the error resulting in a seven-fold improvement compared to timed implantation, allowing us to better estimate the conversion yield of implanted Si to SiV. We detect SiV emitters by photoluminescence spectroscopy, determine the number of emitters per location and calculate the yield to be 2.98 + 0.21 / - 0.24 %. Candidates for single photon emitters are investigated further by Hanbury-Brown-Twiss interferometry confirming that 82 % of the locations exhibit single photon emission statistics. This counted ion implantation technique paves the way towards deterministic creation of SiV when ion counting is used in combination with methods that improve the activation yield of SiV.

quant-ph↗

arXiv2017

Effective g factor of low-density two-dimensional holes in a Ge quantum well

We report measurements of the effective $g$ factor of low-density two-dimensional holes in a Ge quantum well. Using the temperature dependence of the Shubnikov-de Haas oscillations, we extract the effective $g$ factor in a magnetic field perpendicular to the sample surface. Very large values of the effective $g$ factor, ranging from $\sim13$ to $\sim28$, are observed in the density range of $1.4\times10^{10}$ cm$^{-2}$ to $1.4\times10^{11}$ cm$^{-2}$. When the magnetic field is oriented parallel to the sample surface, the effective $g$ factor is obtained from a protrusion in the magneto-resistance data that signifies full spin polarization. In the latter orientation, a small effective $g$ factor, $\sim1.3-1.4$, is measured in the density range of $1.5\times10^{10}$ cm$^{-2}$ to $2\times10^{10}$ cm$^{-2}$. This very strong anisotropy is consistent with theoretical predictions and previous measurements in other 2D hole systems, such as InGaAs and GaSb.

cond-mat.mes-hall↗