Coherent electron focusing

Abstract

Summnry: Thcory and cxpcrimcnl arc rcvicwcd οΓ Ihc clussical and quantum mcchanical focusing by a niagncüc fickl of ballislic clcctrons injcctcd tlirough a point contact in a Uvo-dimcnsional electron gas. Two altcrnalivc poinLs of vicw arc cmphasizcd. On thc onc band, thc cxpcrimcnL i s n rcalizntion ofclcclron oplics in Ihc solid stalc. Thc thrcc basic building blocks arc a cohcicnt and monochromalic point sourcc/dctcctor, an elcctrostalic mirror wilh littlc diffuse scatlcring, and a magnclic Icns. On thc othcr band, cohcrent clcclron focusing is a rcsislancc mcasurcmcnl in thc quantum ballistic transport rcgime, which cxhibits Ihc charactcristic featurcs of this rcgime in a most extreme way. For cxamplc, largc magnclorcsi.stancc oscillations occur (up to 9.5% amplitudc modulalion is obscrvcd), with a pcriodicily which is non-locally dclcrmincd by thc Separation bctwccn currcnl and vollage point contacLs. Λ WKB calculation of Ihc liansmission probabililics shows lliat Ihis cffect is thc rcsult of thc intcrfcrcncc of cohcrcnlly cxcitcd magnctic edgc slalcs al the electron gas boundary, Anothcr cxamplc is thc abscncc of local cquilibrium: Thc mcasurcmcnts shovv that thc point conlacts can sclectivcly populatc (and clelcct) specific Land au Icvcls, and that Ihis highly non-cquilibrium population is mainlaincd ovcr dislances of microns.

Weak antilocalization and conductance fluctuation in a single crystalline Bi nanowire

“…For a mesoscopic system with disorder and strong spin-orbit coupling, the phase coherent magneto-transport at low temperatures result in the appearance of weak antilocalization (WAL) and universal conductance fluctuations (UCF) effects. [10][11][12] These phenomena are affected by the phase-coherence length, l a , defined as the length where phase-coherent transport is preserved. Therefore, WAL and UCF are commonly used in determining the phase-coherence length of a material system.…”

“…The first is the narrow valley originating from WAL near the zero magnetic field. 10,14 Usually, WAL occurs when the strong spin-orbit interaction reverses the sign of the resistance correction in the weak localization (WL) phenomena. Without a strong spin-orbit coupling, the WL effect can be identified by the increase of resistance near the zero magnetic field because of the conductance correction by electron localization.…”

Submicron processing of InAs based quantum wells: A new, highly selective wet etchant for AlSb

“…2. 15 The Shubnikov-de Haas oscillations observed at high field ͑Fig. 2͒ are due to the series resistance.…”

Anomalous Goos-Hänchen shift in the Floquet scattering of Dirac fermions

“…Many analogies exist between the scattering of an electron beam from electrostatic potentials in 2D electron gases and the one of a light beam from an interface between two media of different refraction index. In condensed matter physics they have been recognized and exploited long ago as for instance in the early beginning of quantum transport in mesoscopic heteroestructures [46][47][48]. Very recently, the analogy has been pushed even further, to the realm of metamaterials [49], with the proposal to construct Veselago lenses using pn junctions in graphene [50,51] to effectively built a negative refraction index for electrons.…”