Propagation of superconducting coherence via chiral quantum-Hall edge channels

Recently, there has been significant interest in superconducting coherence via chiral quantum-Hall (QH) edge channels at an interface between a two-dimensional normal conductor and a superconductor (N-S) in a strong transverse magnetic field. In the field range where the superconductivity and the QH state coexist, the coherent confinement of electron-and hole-like quasiparticles by the interplay of Andreev reflection and the QH effect leads to the formation of Andreev edge states (AES) along the N-S interface. Here, we report the electrical conductance characteristics via the AES formed in graphene-superconductor hybrid systems in a three-terminal configuration. This measurement configuration, involving the QH edge states outside a graphene-S interface, allows the detection of the longitudinal and QH conductance separately, excluding the bulk contribution. Convincing evidence for the superconducting coherence and its propagation via the chiral QH edge channels is provided by the conductance enhancement on both the upstream and the downstream sides of the superconducting electrode as well as in bias spectroscopy results below the superconducting critical temperature. Propagation of superconducting coherence via QH edge states was more evident as more edge channels participate in the Andreev process for high filling factors with reduced valley-mixing scattering.115Ysciescopu

The Physico-Chemical and Microbiological Water Quality of the Artificial Lake Keumgang

This study was performed to investigate the changing encironment of Keum River after the construction of the floodgate at the mouth of Keum River. Samples were taken from the surface wateres at 3 stations near the floodgate of the artificial lake Keumgang to measure the physico-chemikcal and microbiological water qualities from May, 2001 to April, 2002. The results were as follows; water temperature ranged from 2 to 28℃, and pH values caried from 7.5 to 9.1 respectively. The dissolced oxygen contents and COD of each station varied from 7.13 to 14.10 mg l⁻¹ and from 5.2 to 9.4 mg l⁻¹resoectively. And total nitrogen and total phosphate values varied from 0.99 to 3.15 mg l⁻¹, and from 0.01 to 0.12 mg l⁻¹ during survey periods,which meant the sampling stations have set in eutrophic level The population density of heterotrophic bacteria ranged from 0.4±0.1 x 103 cfu ml⁻¹ to 3.5±0.6 x 10³cfu ml⁻¹ for during survey periods. The population densities of physiological groups of aerobic bacteria ranged from 2.0±1.0 x 10² to 1.7±0.2 x 10³ cfu ml⁻¹ for amylolytic bacteria, from 0.3±0.1 x 10² to 1.3±+0.5 x 10³ cfu ml⁻¹ for proteolytix bacteria, from 0.2±0.1 x 10³ to 4.9±1.3 x 10³ cfu ml⁻¹ for lipolytic bacteria, and from 0.2±0.1 x 10² to 2.7±0.7 x 10³ cfu ml⁻¹ for cellulolytic bacteria during survey periods, respectively. Among the measured numbers of physiological groups of bacteria, lipolytic bacteria showed the highest population density. Howecer, the numbers of amylolytic, pyoteolytic, and cellulolylic bacteria showed the similar tendency.Article信州大学山地水環境教育研究センター研究報告 2: 57-61(2004)departmental bulletin pape

Negative refractive transport of electrons in ballistic graphene

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Propagation of superconducting coherence via chiral quantum-Hall edge channels

Abstract Recently, there has been significant interest in superconducting coherence via chiral quantum-Hall (QH) edge channels at an interface between a two-dimensional normal conductor and a superconductor (N–S) in a strong transverse magnetic field. In the field range where the superconductivity and the QH state coexist, the coherent confinement of electron- and hole-like quasiparticles by the interplay of Andreev reflection and the QH effect leads to the formation of Andreev edge states (AES) along the N–S interface. Here, we report the electrical conductance characteristics via the AES formed in graphene–superconductor hybrid systems in a three-terminal configuration. This measurement configuration, involving the QH edge states outside a graphene–S interface, allows the detection of the longitudinal and QH conductance separately, excluding the bulk contribution. Convincing evidence for the superconducting coherence and its propagation via the chiral QH edge channels is provided by the conductance enhancement on both the upstream and the downstream sides of the superconducting electrode as well as in bias spectroscopy results below the superconducting critical temperature. Propagation of superconducting coherence via QH edge states was more evident as more edge channels participate in the Andreev process for high filling factors with reduced valley-mixing scattering

Engineering Crossed Andreev Reflection in Double-Bilayer Graphene

Crossed Andreev reflection (CAR) is a non local process that converts an incoming electron (hole) from one normal electrode to an out-going hole (electron) in another normal electrode through a superconductor (SC). CAR corresponds to the inverse process of Cooper pair splitting, which generates a quantum-entangled electron pair with spatial separation. Here, we fabricated vertically stacked double bilayer graphene (BLG) connected via a superconducting electrode and achieved a spacing between BLG sheets of similar to 44 nm, which is far shorter than the superconducting coherence length. We confirm the highly efficient CAR effect by observing strong negative differential resistance in a nonlocal configuration and demonstrate that the competing processes against the CAR can be effectively suppressed by separately tuning the chemical potential of each BLG. The dependence of nonlocal signals on bias voltage, temperature, and chemical potential is consistent with the predicted CAR process. Our results provide a new pathway to a novel SC-based quantum entangler with the in situ tunability of the correlated-pair-splitting efficiency.11Nsciescopu

Transport measurements of negative refractive behavior in ballistic graphene hetero-junctions

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Progress report on the realization of Veselago's lens with high mobility graphene

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Microstructure and mechanical properties of a gas-tungsten-arc-welded Fe-24Mn-3.5Cr-0.4C high manganese steel pipe using a Fe-22Mn-2.34Ni-0.38C welding wire

In this study, Fe-24.34Mn-3.53Cr-0.42C high manganese steel sheets were joined using a gas-tungsten arc welding (GTAW) and a plasma arc welding (PAW) using a newly-developed Fe-22.2Mn-2.34Cr-1.95Ni welding wire. Microstructure analysis revealed that Mn-depleted zone appeared in the weld zone due to Mn segregation during solidification. With plastic deformation, a small amount of epsilon-martensite was found in the Mn-depleted zone i.e., dendritic region, of the weld zone. Mechanical properties of the weld zone were found to be lower than in the base metal. On the other hand, due to recrystallization and grain growth induced by heat treatment at 1050 degrees C, the mechanical property differences between the base metal and the weld zone were reduced. Strain rate sensitivity test showed negative strain rate sensitivity in the base metal and heat-treated weld zone possibly due to the reduced work hardening caused by the reduction of twinning nucleation. On the contrary, the as -welded zone exhibited positive strain rate sensitivity due to the reduction in twinning stress caused by coarse grains