arXiv subjects

J. C. Woo

Publications and source records attributed to J. C. Woo.

5 recordsLinked to original sources

arXiv2006

Interplay between carrier and impurity concentrations in annealed Ga$_{1-x}$Mn$_{x}$As intrinsic anomalous Hall Effect

Investigating the scaling behavior of annealed Ga$_{1-x}$Mn$_{x}$As anomalous Hall coefficients, we note a universal crossover regime where the scaling behavior changes from quadratic to linear, attributed to the anomalous Hall Effect intrinsic and extrinsic origins, respectively. Furthermore, measured anomalous Hall conductivities when properly scaled by carrier concentration remain constant, equal to theoretically predicated values, spanning nearly a decade in conductivity as well as over 100 K in T$_{C}$. Both the qualitative and quantitative agreement confirms the validity of new equations of motion including the Berry phase contributions as well as tunablility of the intrinsic anomalous Hall Effect.

cond-mat.mtrl-sci↗

arXiv2006

Evidence of metallic clustering in annealed Ga1-xMnxAs from atypical scaling behavior of the anomalous Hall coefficient

We report on the anomalous Hall coefficient and longitudinal resistivity scaling relationships on a series of annealed Ga1-xMnxAs epilayers (x~0.055). As-grown samples exhibit scaling parameter n of ~ 1. Near the optimal annealing temperature, we find n ~ 2 to be consistent with recent theories on the intrinsic origins of anomalous Hall Effect in Ga1-xMnxAs. For annealing temperatures far above the optimum, we note n > 3, similar behavior to certain inhomogeneous systems. This observation of atypical behavior agrees well with characteristic features attributable to spherical resonance from metallic inclusions from optical spectroscopy measurements.

cond-mat.mtrl-sci↗

arXiv2005

Near-field spectroscopy of bimodal size distribution of InAs/AlGaAs quantum dots

We report on high-resolution photoluminescence (PL) spectroscopy of spatial structure of InAs/AlGaAs quantum dots (QDs) by using a near-field scanning optical microscope (NSOM). The double-peaked distribution of PL spectra is clearly observed, which is associated with the bimodal size distribution of single QDs. In particular, the size difference of single QDs, represented by the doublet spectral distribution, can be directly observed by the NSOM images of PL.

physics.optics↗

arXiv2005

Near-field photoluminescence study of InAs/AlGaAs quantum-dot-based nanoclusters: band filling effect

We have performed near-field spectroscopy and microscopy of the InAs/AlGaAs quantum-dot-based nanoclusters. It is observed that the photoluminescence spectra of spatially confined excitons in the nanoclusters is blue-shifted up to 20 meV as the power density is increased. In particular, the near-field photoluminescence images have shown that excitons became spatially confined gradually from lower energy state (1.4150 eV) to higher energy state (1.4392 eV) as the excitation power is increased, which is indicative of the band-filling effect of semiconductor nanostructures.

physics.optics↗

arXiv1998

Spin-Landau Orbit Coupling in Units of the Flux Quantum Observed from Zeeman Splitting of a Quantum Wire Array

In Zeeman spectra of a GaAs-AlGaAs quantum wire array with superlattice period lp, the zero-field shift is found to increase in steps of (2 pi hbar/ e)lp^{-2} at the cyclotron radius Rc ~lp, lp/2, and lp/3. This shift, caused by spin-Landau orbit coupling and quantized in units of the flux quantum 2 pi hbar /e,is a manifestation of the gauge invariance, and the first observation of the flux quantization in a non-superconducting material.The quantum interference associated with the phase difference in the quantum barrier scattering is also reported.

cond-mat.mes-hall↗