We theoretically study the differential conductance of a graphene/graphene superconductor junction, where the valley polarization of Dirac electrons is considered in the nonsuperconducting region. It is shown that the...We theoretically study the differential conductance of a graphene/graphene superconductor junction, where the valley polarization of Dirac electrons is considered in the nonsuperconducting region. It is shown that the subgap conductance will increase monotonically with the valley-polarization strength when the chemical potential μ is near the Dirac point μ≤ 3？（？ is the superconducting gap）, whereas it will decrease monotonically when μ is far away from the Dirac point, μ≥ 5？.The former case is induced by the specular Andreev reflection while the retro-reflection accounts for the later result. Our findings may shed light on the control of conductance of a graphene superconductor junction by valley polarization.展开更多
Mesa-structured intrinsic Josephson junctionsare fabricated in Bi2Sr2CaCu2O8+x single crystals. Typicalcurrent-voltage characteristics of intrinsic Josephson junc-tions are observed, which include multiple quasi-parti...Mesa-structured intrinsic Josephson junctionsare fabricated in Bi2Sr2CaCu2O8+x single crystals. Typicalcurrent-voltage characteristics of intrinsic Josephson junc-tions are observed, which include multiple quasi-particle branches, surface junction with critical current lower than those of inner junctions, and subgap structures on quasi-particle branches. The corresponding physical explanationsare also given. The energy gap voltage of the intrinsicJosephson junctions at 30 K is about 20 mV. Besides, themeasured Ic-T relationship agrees quite well with thetheoretical computations based on -22-wavexyd supercon-ductor. Our measured dI/dV-V relationship shows theV-shaped gap structure, obviously differing from theU-shaped gap structure of the s-wave superconductor.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11274059 and 11074233)
文摘We theoretically study the differential conductance of a graphene/graphene superconductor junction, where the valley polarization of Dirac electrons is considered in the nonsuperconducting region. It is shown that the subgap conductance will increase monotonically with the valley-polarization strength when the chemical potential μ is near the Dirac point μ≤ 3？（？ is the superconducting gap）, whereas it will decrease monotonically when μ is far away from the Dirac point, μ≥ 5？.The former case is induced by the specular Andreev reflection while the retro-reflection accounts for the later result. Our findings may shed light on the control of conductance of a graphene superconductor junction by valley polarization.
基金This work was partially done in Research Institute of Elec-trical Communication Tohoku University+1 种基金 Japan and supported by the Ministry of Science and Technology of China (Grant No. G19990646).
文摘Mesa-structured intrinsic Josephson junctionsare fabricated in Bi2Sr2CaCu2O8+x single crystals. Typicalcurrent-voltage characteristics of intrinsic Josephson junc-tions are observed, which include multiple quasi-particle branches, surface junction with critical current lower than those of inner junctions, and subgap structures on quasi-particle branches. The corresponding physical explanationsare also given. The energy gap voltage of the intrinsicJosephson junctions at 30 K is about 20 mV. Besides, themeasured Ic-T relationship agrees quite well with thetheoretical computations based on -22-wavexyd supercon-ductor. Our measured dI/dV-V relationship shows theV-shaped gap structure, obviously differing from theU-shaped gap structure of the s-wave superconductor.
