arXiv subjects

David Ritchie

Publications and source records attributed to David Ritchie.

23 records · Page 2Linked to original sources

arXiv2016

Observation of geometry dependent conductivity in two-dimensional electron systems

We report electrical conductivity $σ$ measurements on a range of two-dimensional electron gases (2DEGs) of varying linear extent. Intriguingly, at low temperatures ($T$) and low carrier density ($n_{\mathrm{s}}$) we find the behavior to be consistent with $σ\sim L^α$, where $L$ is the length of the 2DEG along the direction of transport. Importantly, such scale-dependent behavior is precisely in accordance with the scaling hypothesis of localization~[Abrahams~\textit{et al.}, Phys. Rev. Lett. \textbf{42}, 673 (1979)] which dictates that in systems where the electronic wave function $ξ$ is localized, $σ$ is not a material-specific parameter, but depends on the system dimensions. From our data we are able to construct the "$β$-function" $\equiv (h/e^2) d \ln σ/ d \ln L$ and show this to be strongly consistent with theoretically predicted limiting values. These results suggest, remarkably, that the electrons in the studied 2DEGs preserve phase coherence over lengths $\sim~10~μ$m. This suggests the utility of the 2DEGs studied towards applications in quantum information as well as towards fundamental investigations into many-body localized phases.

cond-mat.mes-hall↗

arXiv2015

Determining energy relaxation length scales in two-dimensional electron gases

We present measurements of the energy relaxation length scale $\ell$ in two-dimensional electron gases (2DEGs). A temperature gradient is established in the 2DEG by means of a heating current, and then the elevated electron temperature $T_e$ is estimated by measuring the resultant thermovoltage signal across a pair of deferentially biased bar-gates. We adapt a model by Rojek and König [Phys. Rev. B \textbf{90}, 115403 (2014)] to analyse the thermovoltage signal and as a result extract $\ell$, $T_e$, and the power-law exponent $α_i$ for inelastic scattering events in the 2DEG. We show that in high-mobility 2DEGs, $\ell$ can attain macroscopic values of several hundred microns, but decreases rapidly as the carrier density $n$ is decreased. Our work demonstrates a versatile low-temperature thermometry scheme, and the results provide important insights into heat transport mechanisms in low-dimensional systems and nanostructures. These insights will be vital for practical design considerations of future nanoelectronic circuits.

cond-mat.mes-hall↗

arXiv2014

Many-body effects in a quasi-one-dimensional electron gas

We have investigated electron transport in a quasi-one dimensional (quasi-1D) electron gas as a function of the confinement potential. At a particular potential configuration, and electron concentration, the ground state of a 1D quantum wire splits into two rows to form an incipient Wigner lattice. It was found that application of a transverse magnetic field can transform a double-row electron configuration into a single-row due to magnetic enhancement of the confinement potential. The movements of the energy levels have been monitored under varying conditions of confinement potential and in-plane magnetic field. It is also shown that when the confinement is weak, electron occupation drives a reordering of the levels such that the normal ground state passes through the higher levels. The results show that the levels can be manipulated by utilising their different dependence on spatial confinement and electron concentration, thus enhancing the understanding of many body interactions in mesoscopic 1D quantum wires.

cond-mat.mes-hall↗

arXiv2005

Zero-bias anomaly and Kondo-assisted quasi-ballistic 2D transport

Nonequilibrium transport measurements in mesoscopic quasi-ballistic 2D electron systems show an enhancement in the differential conductance around the Fermi energy. At very low temperatures, such a zero-bias anomaly splits, leading to a suppression of linear transport at low energies. We also observed a scaling of the nonequilibrium characteristics at low energies which resembles electron scattering by two-state systems, addressed in the framework of two-channel Kondo model. Detailed sample-to-sample reproducibility indicates an intrinsic phenomenon in unconfined 2D systems in the low electron-density regime.

cond-mat.mes-hall↗

arXiv2002

A Virtual Library of Technical Publications

Through a collaborative effort, the Fermilab Information Resources Department and Computing Division have created a "virtual library" of technical publications that provides public access to electronic full-text documents. This paper will discuss the vision, planning and milestones of the project, as well as the hardware, software and interdepartmental cooperation components.

cs.DL↗