Anomalous spin Josephson effect in spin superconductors

The spin superconductor state is the spin-polarized triplet exciton condensate,which can be viewed as a counterpart of the charge superconductor state.As an analogy of the charge Josephson effect,the spin Josephson effect can be generated in the spin superconductor/normal metal/spin superconductor junctions.Here we study the spin supercurrent in the Josephson junctions consisting of two spin superconductors with noncollinear spin polarizations.For the Josephson junctions with out-of-plane spin polarizations,the possibleπ-state spin supercurrent appears due to the Fermi momentum-splitting Andreev-like reflections at the normal metal/spin superconductor interfaces.For the Josephson junctions with in-plane spin polarizations,the anomalous spin supercurrent appears and is driven by the misorientation angle of the in-plane polarizations.The symmetry analysis shows that the appearance of the anomalous spin Josephson current is possible when the combined symmetry of the spin rotation and the time reversal is broken.

Anomalous Josephson effect between d-wave superconductors through a two-dimensional electron gas with both Rashba spin-orbit coupling and Zeeman splitting

Based on the Bogoliubov-de Gennes equation and the extended McMillan’s Green’s function formalism,we study theoretically the Josephson effect between two d-wave superconductors bridged by a ballistic two-dimensional electron gas with both Rashba spin-orbit coupling and Zeeman splitting.We show that due to the interplay of Rashba spin-orbit coupling and Zeeman splitting and d-wave pairing,the current-phase relation in such a heterostructure may exhibit a series of novel features and can change significantly as some relevant parameters are tuned.In particular,anomalous Josephson current may occur at zero phase bias under various different situations if both time reversal symmetry and inversion symmetry of the system are simultaneously broken,which can be realized by tuning some relevant parameters of the system,including the relative orientations and the strengths of the Zeeman field and the spin-orbit field in the bridge region,the relative orientations of the a axes in two superconductor leads,or the relative orientations between the Zeeman field in the bridge region and the a axes in the superconductor leads.We show that both the magnitude and the direction of the anomalous Josephson current may depend sensitively on these relevant parameters.

New Derivation of Simple Josephson Effect Relation Using New Quantum Mechanical Equation

A relation of the Josephson current density equation is successfully derived;this is done through a new derivation of the equation of quantum by neglecting kinetic Newtonian term in the energy expression.

Anomalous Direct-Current Josephson Effect in Semiconductor Nanowire Junctions

We investigate the dc Josephson effect in one-dimensional junctions where a ring conductor is sandwiched between two semiconductor nanowires with proximity-induced superconductivity. Peculiar features of the Josephson effect arise due to the interplay of spin-orbit interaction and external Zeenmn field. By tuning the Zeeman field orientation, the device can vary from 0 to π junction. Afore importantly, nonzero ,losephson current is possible at zero phase difference across the junction. Although this anomalous Josephson current is not relevant to the topological phase transition, its magnitude can be significantly enhanced whe, n the nanowire, s become topological superconductors where Majorana bound states emerge. Distinct modulation patterns are obtained for the semiconductor nanowires in the topologically trivial and non-trivial phases. These results are useful to probe the topological phase transition in semiconductor nanowire junctions via the dc Josephson effect.

Ac Josephson effect in Corbino-geometry Josephson junctions constructed on Bi_(2)Te_(3) surface

Recently, a Corbino-geometry type of Josephson junction constructed on the surface of topological insulators has been proposed for hosting and braiding Majorana zero modes. As a first step to test this proposal, we successfully fabricated Corbino-geometry Josephson junctions(JJs) on the surface of Bi_(2)Te_(3) flakes. Ac Josephson effect with fractional Shapiro steps was observed in the Corbino-geometry JJs while the flux in the junction area was quantized. By analyzing the experimental data using the resistively shunted Josephson junction model, we found that the Corbino-geometry JJs exhibit a skewed current-phase relation due to its high transparency. The results suggest that Corbino-geometry JJs constructed on the surface of topological insulators may provide a promising platform for studying Majorana-related physics.

Influence of Rashba spin–orbit coupling on Josephson effect in triplet superconductor/two-dimensional semiconductor/triplet superconductor junctions

We study theoretically Josephson effect in a planar ballistic junction between two triplet superconductors with pwave orbital symmetries and separated by a two-dimensional(2D)semiconductor channel with strong Rashba spin–orbit coupling.In triplet superconductors,three types of orbital symmetries are considered.We use Bogoliubov–de Gennes formalism to describe quasiparticle propagations through the junction and the supercurrents are calculated in terms of Andreev reflection coefficients.The features of the variation of the supercurrents with the change of the strength of Rashba spin–orbit coupling are investigated in some detail.It is found that for the three types of orbital symmetries considered,both the magnitudes of supercurrent and the current-phase relations can be manipulated effectively by tuning the strength of Rashba spin–orbit coupling.The interplay of Rashba spin–orbit coupling and Zeeman magnetic field on supercurrent is also investigated in some detail.

Josephson effect in the strontium titanate/lanthanum aluminate junction

We report theoretical studies on the newly discovered novel Josephson effect and scanning tunneling spectroscopy(STS) at the interface of strontium titanate/lanthanum aluminate(STO/LAO).With a phenomenological boson-fermion model, the density of states is calculated and the results are consistent with the STS experiments.A typical calculation of Josephson effect is performed, and it is in qualitative agreement with the experiments.The calculations indicate that the gap states come from the pairing of quasi-particles with a finite total momentum and the Josephson current comes from the tunneling of quasi-particle pairs with zero momentum.The quasi-particles are Bogoliubov quasi-particles.Moreover, the fits using Kulik's formula imply that the Josephson junction at the STO/LAO interface has a point contact with the clean superconductor limit.

Reveal the nematic topological superconductivity from the anisotropic unconventional Josephson effect:Theory and application to doped Bi_(2)Se_(3)

We propose a scheme to reveal the possible nematic superconducting order parameter in the doped Bi2Se3 by observing the anisotropic unconventional Josephson effect without an external magnetic field.We find the presence of an intrinsicπ-phase in the spin-triplet channel of Andreev reflection.Its competition with the odd-parity superconducting gap phase can lead to unconventional Josephson effect in the Josephson junction,whose normal region is connected to the same side of the superconductor,called the U-shaped junction according to its geometry.For Josephson junctions with the interfaces perpendicular to the nematic direction,the competition will lead to a Josephsonπ-junctions.In the case where the interface is parallel to the nematic direction,it will lead to a Josephson 0-junction.Thus,this can directly reflect the nematic superconductivity.It is worth noting that Josephson coupling with the 4πperiod appears only in the normal injected channels.Interestingly,if the Josephson junction adopts a conventional geometry,it always exhibits a normal Josephson 0-junction regardless of the gap function taken by the doped Bi2Se3 and therefore cannot distinguish the pairing symmetry.We thus propose a superconducting quantum interference device containing a U-shaped Josephson junction to detect nematic superconductivity.This proposal not only can be applied to detect nematic superconductivity but also provides a feasible platform for topological quantum computation.

一个带阻尼项Josephson振动的半经典模型

在双势阱模型的基础上考虑了Josephson流与凝聚体的相互作用而引起的阻尼效应,得出相对粒子数Z(t)的表达式,并用一个简单的碰撞模型得出Josephson振动的振幅和能量及随时间呈指数衰减,以及凝聚体的质量越大,衰减越慢。

SSeS超导结的Josephson效应

以推广了的Jacobson方法 ,由Ginzburg Landau方程出发 ,推导出了SSeS超导结的直流Josephson效应 .从而进一步求得了SSeS超导结的临界电流与温度之间的关系 ,以及对结区厚度的依赖性 .

Josephson junction of two-species Bose-Einstein condensates in a high-finesse optical cavity

The mean-field dynamics of undistinguishable two-species Bose Josephson junction coupled to a single mode high- finesse optical cavity is investigated. From the Hamiltonian, the phase portrait and the stationary points are given. It is shown that the role of the interspecies interaction equals the intraspecies interaction under suitable conditions. As the interspecies interaction increases, the trapped atoms will start tunneling between the two wells unnaturally for some special cases.

Josephson效应非线性特性的研究

用等效电路理论分析实际的Josephson结 ,并讨论在噪声作用下Josephson结的非线性特性 ,所得结果为Josephson器件的研究和应用提供了依据 .

直流和交流Josephson效应的研究

基于Feynman模型得到的Josephson方程,在求解过程中采取了ρ1=ρ2的假设,但这个假设在数学处理上并不严格。为了得到严格的结果,未进行上述假设,通过解微分方程得到了严格的Josephson方程,结果显示在一定条件下才能得到通常所说的Josephson方程。

外场中超导体/半导体/超导体结的直流Josephson电流

当外加磁场时,超导体/半导体/超导体结的临界电流受外加磁场的影响.超导结的临界电流与磁场的曲线非常类似于单色光在单狭缝衍射的夫琅和费图样.在未考虑外加磁场的超导体/半导体/超导体结的临界电流的基础上,进一步对外加磁场的情形进行了研究.

一个描述Josephson振动阻尼效应的场方程

在GPE方程的基础上添加了一个耗散项-1/2γcψ,用来分析双势阱模型的Josephson振荡中的阻尼现象,并得出:凝聚态粒子总数及Josephson振动的振幅随时间呈指数衰减。

Novel 0–π transitions in Josephson junctions between noncentrosymmetric superconductors

We study the Josephson effect between two noncentrosymmetric superconductors（NCSs） with opposite polarization vectors of Rashba spin–orbit coupling（RSOC）.We find a 0–π transition driven by the triplet–singlet ratio of NCSs.Different from conventional 0–π transitions,the Andreev bound states change their energy range instead of phase shift in the 0–π transition found here.This novel property results in a feature that the critical current becomes almost zero at the transition point,not only a minimum.Furthermore,when the directions of RSOC polarization vectors are the same in two NCSs,the similar effect can also be found in the presence of a perpendicular exchange field or a Dresselhause spin–orbit coupling in the interlayer.We find novel oscillations of critical current without 0–π transition.These novel 0–π transitions or oscillations of critical current present new understanding of the Josephson effect and can also serve as a tool to determine the unknown triplet–singlet ratio of NCSs.

Josephson结的理论模型和特性分析

对Josephson结的一种理论模型 (Sterwart McCumber模型 )进行了研究 ,通过求解其相应的Fokker planck方程 ,得到热涨落存在时Josephson结的电流 -电压特性曲线 .结果表明 :热涨落对Josephson结的电流 -电压特性会产生较大的影响 .

热涨落对Josephson效应的影响

采用模拟粒子在势场中的布朗运动去讨论热涨落对小电容时Josephson效应的影响 ,得到热涨落存在时Joseph son结的电流—电压特性 。

对Josephson效应I-V特性的理论研究

用RSJ模型的概率分布函数研究了热涨落对Josephson效应的影响 ,得到了热涨落存在时Josephson结的电流 -电压特性 。

传统和非传统超导体间的Josephson隧道

运用准粒子自洽场方法计算了传统和非传统超导体间的Ｊｏｓｅｐｈｓｏｎ电流。计算表明临界电流极强地依赖于两个晶体和结的相对取向，并在某些特殊的相对取向变为零。同时证明，由于自旋轨道耦合。