It is known that in the two-dimensional disordered superconductors electron-electron interactions in the Cooper channel lead to the negative logarithmic in temperature correction to the tunneling conductance above the critical temperature. Physically this result appears due to the density of states suppression by superconductive fluctuations near the Fermi level. It is interesting that the other correction, which accounts for the Maki-Thompson-type interaction of fluctuations, is positive and exhibits strong power law, which dominates the logarithmic term in the immediate vicinity of the critical temperature. An interplay between these two contributions determines the zero-bias anomaly in fluctuating superconductors. This paper is devoted to the fate of such interaction corrections in the ballistic superconductors. It turns out that ballistic dynamic fluctuations perturb single-particle density of states near the Fermi level at the energy scale which is different from that in the diffusive case. As the consequence, fluctuation region becomes much broader. In this regime we confirm that correction to the tunneling conductance remains negative and logarithmic not too close to the critical temperature while in the immediate vicinity of the transition we find novel power law for the Maki-Thompson contribution. It is suggested that peculiar non-monotonous temperature dependence of the tunneling conductance may be probed via magneto-tunnel experiments.
Conductance of non-ballistic point contacts in hybrid systems "normal metal/superconductor" Cu/Mo-C and Cu/LaOFFeAs
我们考虑的非弹道点接触NS异质系统的“Andreev”电导曲线的形状取决于在接触的偏置电压。所获得的这些曲线的形状是由来自杂质的相干散射机制的贡献引起的，该相干散射机制使散射截面加倍。广义和微分电导的行为进行了比较弹道和非弹道输运制度。标准被认为是允许一个区分这些制度与相应的传导曲线相似的外观。分析扩展到NS点接触与外来超导体，碳化钼Mo-C和氧铌酸镧La[O $_{1-x}$ F $_{x}$ ]FeAs从一组铁基超导体的非弹道输运的情况。
Surface adatom conductance filtering in scanning tunneling spectroscopy of Co-doped BaFe2As2 iron pnictide superconductors
我们建立在从头算理论和实验相结合，在扫描隧道显微镜/光谱的A-122铁pnictide超导体的隧穿过程-在这种情况下BaFe $_{2-x}$ Co $_x$ As $_2$ -涉及一个强大的吸附原子过滤的微分电导从近EF Fe 3d状态，这反过来又源于最顶部的子表面Fe层的晶体。计算结果表明，表面Ba相关的隧穿途径的主导地位留下的指纹中发现的实验微分电导数据，包括大粒子空穴不对称性和能量依赖的对比度反转。
Quantum transport in ballistic $s_\pm$-wave superconductors with interband coupling: conductance spectra, Josephson current, and crossed Andreev reflection
We study coherent transport and bound-state formation of Bogoliubov quasiparticles in a high-mobility In$_{0.75}%$Ga$_{0.25}$As two-dimensional electron gas (2DEG) coupled to a superconducting Nb electrode by means of a quantum point contact (QPC) as a tunable single-mode probe. Below the superconducting critical temperature of Nb, the QPC shows a single-channel conductance greater than the conductance quantum $2e^{2}/h$ at zero bias, which indicates the presence of Andreev-reflected quasiparticles, time-reversed states of the injected electron, returning back through the QPC. The marked sensi…
In the "ballistic" regime, the transport across a normal metal (N)/superconductor (S) point-contact is dominated by a quantum process called Andreev reflection. Andreev reflection causes an enhancement of the conductance below the superconducting energy gap, and the ratio of the low-bias and the high-bias conductance cannot be greater than 2 when the superconductor is conventional in nature. In this regime, the features associated with Andreev reflection also provide energy and momentum-resolved spectroscopic information about the superconducting phase. Here we theoretically consider various t…
