arXiv subjects

A. P. Micolich

Publications and source records attributed to A. P. Micolich.

61 records · Page 4Linked to original sources

arXiv2006

Anisotropic Zeeman splitting in ballistic one-dimensional hole systems

We have studied the effect of an in-plane magnetic field B on a one-dimensional hole system in the ballistic regime created by surface gate confinement. We observed clearly the lifting of the spin degeneracy due to the Zeeman effect on the one dimensional subbands for B applied parallel to the channel. In contrast, no Zeeman splitting is detected for B applied perpendicular to the channel, revealing an extreme anisotropy of the effective Lande g-factor g*. We demonstrate that this anisotropy is a direct consequence of the one-dimensional confinement on a system with strong spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2006

Zeeman splitting in ballistic hole quantum wires

We have studied the Zeeman splitting in ballistic hole quantum wires formed in a (311)A quantum well by surface gate confinement. Transport measurements clearly show lifting of the spin degeneracy and crossings of the subbands when an in-plane magnetic field B is applied parallel to the wire. When B is oriented perpendicular to the wire, no spin-splitting is discernible up to B = 8.8 T. The observed large Zeeman splitting anisotropy in our hole quantum wires demonstrates the importance of quantum-confinement for spin-splitting in nanostructures with strong spin-orbit coupling.

cond-mat.mes-hall↗

arXiv2006

Superconductivity in Metal-mixed Ion-Implanted Polymer Films

Ion-implantation of normally insulating polymers offers an alternative to depositing conjugated organics onto plastic films to make electronic circuits. We used a 50 keV nitrogen ion beam to mix a thin 10 nm Sn/Sb alloy film into the sub-surface of polyetheretherketone (PEEK) and report the low temperature properties of this material. We observed metallic behavior, and the onset of superconductivity below 3 K. There are strong indications that the superconductivity does not result from a residual thin-film of alloy, but instead from a network of alloy grains coupled via a weakly conducting, ion-beam carbonized polymer matrix.

cond-mat.supr-con↗

arXiv2005

Conductance quantization and the 0.7x2e2/h conductance anomaly in one-dimensional hole systems

We have studied ballistic transport in a 1D channel formed using surface gate techniques on a back-gated, high-mobility, bilayer 2D hole system. At millikelvin temperatures, robust conductance quantization is observed in the quantum wire formed in the top layer of the bilayer system, without the gate instabilities that have hampered previous studies of 1D hole systems. Using source drain bias spectroscopy, we have measured the 1D subband spacings, which are 5-10 times smaller than in comparable GaAs electron systems, but 2-3 times larger than in previous studies of 1D holes. We also report the first observation of the anomalous conductance plateau at G = 0.7 x 2e2/h in a 1D hole system.

cond-mat.mes-hall↗

arXiv2004

Three Key Questions on Fractal Conductance Fluctuations: Dynamics, Quantization and Coherence

Recent investigations of fractal conductance fluctuations (FCF) in electron billiards reveal crucial discrepancies between experimental behavior and the semiclassical Landauer-Buttiker (SLB) theory that predicted their existence. In particular, the roles played by the billiard's geometry, potential profile and the resulting electron trajectory distribution are not well understood. We present measurements on two custom-made devices - a 'disrupted' billiard device and a 'bilayer' billiard device - designed to probe directly these three characteristics. Our results demonstrate that intricate processes beyond those proposed in the SLB theory are required to explain FCF.

cond-mat.mes-hall↗

arXiv2004

Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance

We use high-mobility bilayer hole systems with negligible tunneling to examine how the bilayer nu = 1 quantum Hall state evolves as charge is transferred from one layer to the other at constant total density. We map bilayer nu = 1 state stability versus imbalance for five total densities spanning the range from strongly interlayer coherent to incoherent. We observe competition between single-layer correlations and interlayer coherence. Most significantly, we find that bilayer systems that are incoherent at balance can develop spontaneous interlayer coherence with imbalance, in agreement with recent theoretical predictions.

cond-mat.mes-hall↗

arXiv2004

Interaction Correction to the Longitudinal Conductivity and Hall Resistivity in High Quality Two-Dimensional GaAs Electron and Hole Systems

We present a systematic study of the corrections to both the longitudinal conductivity and Hall resistivity due to electron-electron interactions in high quality GaAs systems using the recent theory of Zala et al. [Phys. Rev. B 64, 214204 (2001)]. We demonstrate that the interaction corrections to the longitudinal conductivity and Hall resistivity predicted by the theory are consistent with each other. This suggests that the anomalous metallic drop in resistivity at B=0 is due to interaction effects and supports the theory of Zala et al.

cond-mat.str-el↗