Based on computer simulations and theoretical analysis, a new dynamic state is found in inductively coupled intrinsic Josephson junctions in the absence of an external magnetic field. In this state, the plasma oscillation is uniform along the c axis and there are $(2m+1)π$ phase kinks, with $m$ being an integer, periodic and thus non-uniform in the $c$ direction. In the IV characteristics, the state manifests itself as current steps occurring at all cavity modes. Inside the current steps, the plasma oscillation becomes strong, which generates several harmonics in frequency spectra at a given voltage. The recent experiments on terahertz radiations from the mesa of a BSCCO single crystal can be explained in terms of this state.
An array of inductively coupled Josephson junctions is considered and it is shown that in presence of a fast impurity which is a junction with a smaller value of critical current, a small amplitude periodic signal can be detected all elsewhere in the array, when is imposed on the fast component. On the other hand, small amplitude signals which are imposed on the other oscillators in the array have minor effect on the dynamics of the whole
The choice of impedance used to shunt a Josephson junction determines if the charge transferred through the circuit is quantized: a capacitive shunt renders the charge discrete, whereas an inductive shunt leads to continuous charge. This discrepancy leads to a paradox in the limit of large inductances L. We show that while the energy spectra of the capacitively and inductively shunted junction are vastly different, their high-frequency responses become identical for large L. Inductive shunting thus opens the possibility to observe charging effects unimpeded by charge noise.
The Josephson effects associated with quantum tunneling of Cooper pairs manifest as nonlinear relations between the superconductivity phase difference and the bias current and voltage. Many novel phenomena appear, such as Shapiro steps in dc cuurent-voltage (IV) characteristics of a Josephson junction under microwave shining, which can be used as a voltage standard. Inversely, the Josephson effects provide a unique way to generate high-frequency electromagnetic (EM) radiation by dc bias voltage. The discovery of cuprate high-Tc superconductors accelerated the effort to develop novel source of …
Circuit quantum electrodynamics systems are typically built from resonators and two-level artificial atoms, but the use of multi-level artificial atoms instead can enable promising applications in quantum technology. Here we present an implementation of a Josephson junction circuit dedicated to operate as a V-shape artificial atom. Based on a concept of two internal degrees of freedom, the device consists of two transmon qubits coupled by an inductance. The Josephson nonlinearity introduces a strong diagonal coupling between the two degrees of freedom that finds applications in quantum non-dem…
We have studied decoherence in a system where two Josephson-junction flux qubits share a part of their superconducting loops and are inductively coupled. By tuning the flux bias condition, we control the sensitivities of the energy levels to flux noises in each qubit. The dephasing rate of the first excited state is enhanced or suppressed depending on the amplitudes and the signs of the sensitivities. We have quantified the $1/f$ flux noises and their correlations and found that the dominant contribution is by local fluctuations.
A general phenomenological theory describing dynamics of Josephson vortices coupled to wide class of linear waves in layered high-T$_c$ superconductors is developed. The theory is based on hydrodynamic long wave approximation and describes interaction of vortices with electromagnetic, electronic and phonon degrees of freedom on an equal footing. In the limiting cases the proposed theory degenerates to simple models considered earlier. In the framework of the suggested model we undertook the numerical simulation of resistive state in layered superconductors placed in external magnetic field and…
Light scattering by Josephson vortices is theoretically predicted. An experimental set-up for the observation of the effect is proposed. The magnetic field should be parallel to the CuO_2 layers and the crystal surface. The falling light should be at grazing angles, and the Bragg scattering must be almost backscattering. The distance between the columns of the Josephson vortices must be slightly smaller than the light-wavelength. The surface should be very clean and flat in order light scattering by surface terraces and surface roughness to give the relatively small background.
We present a theory of the Josephson effect in a twofold-tilted Josephson junction made by d-wave anisotropic layered superconductors. We find the appearance of an intrinsic electrical resistance that arises from the misalignment of the superconductive planes (the CuO_2 planes in YBCO) in the two electrodes. This intrinsic contribution to the tunnel barrier has several non-trivial consequences. The result is relevant for understanding the electric transport properties of [100] tilt and [100] tilt-tilt Josephson junctions based on d-wave superconductors.
We find systematic signatures suggesting a different superconducting nature for a triple-layered cuprate Bi$_2$Sr$_2$Ca$_2$Cu$_3$O$_{10+δ}$ with respect to a double-layer through the properties of intrinsic Josephson junctions (IJJs). Our measurements on the current-voltage characteristics reveal that the $c$-axis maximum Josephson current density is sensitive to the superfluid density in outer planes while the critical temperature and the superconducting gap remain unaffected. Switching dynamics of stacked IJJs exhibit that the fluctuation in gauge-invariant phase difference of an IJJ implies…
Quantum Advanced Research Center (QuARC), Consejo Superior de Investigaciones Científicas (CSIC)（量子先进研究中心，西班牙国家研究委员会）；Instituto de Ciencia de Materiales de Madrid (ICMM), Consejo Superior de Investigaciones Científicas (CSIC)（马德里材料科学研究所，西班牙国家研究委员会）；Universidad Autónoma de Madrid（马德里自治大学）
Edge critical currents of dense Josephson vortex lattice in layered superconductors
本文计算了沿原子层超导体层施加大磁场$B$所产生的稠密约瑟夫森涡旋晶格的临界电流随场的变化关系。在干净的样品中，由于晶格与边界的相互作用，出现有限的临界电流。边界引起晶格的交替变形，在典型长度处在样品内部衰减，该典型长度大于约瑟夫森长度并且与磁场成比例地增加。这种变形的确切形状和沿表面流动的总电流由晶格在体块中的位置唯一地确定。总的最大约瑟夫森电流具有强振荡的整体1/B依赖性。与公知的夫琅和费依赖性相反，振荡周期对应于添加\emph{one flux quantum per two junctions}。由于与边界的相互作用，慢晶格运动的磁通流电压也随场振荡，与最近的实验一致。
Many superconducting materials are composed of weakly coupled conducting layers. Such a layered structure has a very strong influence on the properties of vortex matter in a magnetic field. This review focuses on the properties of the Josephson vortex lattice generated by the magnetic field applied in the layers direction. The theoretical description is based on the Lawrence-Doniach model in the London limit which takes into account only the phase degree of freedom of the superconducting order parameter. In spite of its simplicity, this model leads to an amazingly rich set of phenomena. We rev…
A new family of dynamic states are found in a stack of inductively coupled intrinsic Josephson junctions in the absence of an external magnetic field. In this state, $(2m_l+1)π$ phase kinks with integers $m_l$'s stack along the c axis and lock neighboring junction together. Large dc power is pumped into plasma oscillation via kinks at the cavity resonance. The plasma oscillation is uniform along the c axis with the frequency satisfying the ac Josephson relation. Thus this state supports strong terahertz radiation and seems to be compatible with the recent experimental observations.
Current - voltage characteristics in magnetic field for layered superconductor with intrinsic pinning of Josephson vortices
M.N. Mikheev Institute of Metal Physics, Ural Branch, Russian Academy of Sciences（俄罗斯科学院乌拉尔分校 M.N. 米凯耶夫金属物理研究所）；National Research Nuclear University MEPhI（国立核研究大学莫斯科工程物理学院）
A new dynamic state characterized by $(2m_l+1)π$ static phase kink with integers $\{m_l\}$ is proposed recently in a stack of inductively coupled Josephson junctions. In the present paper, the stability of the phase kink state is investigated against many perturbations and it is shown that the kink state is stable. It is also discussed that the suppression of the amplitude of superconducting order parameter caused by the kink is weak.
We investigate the response of a stack of intrinsic Josephson junctions (IJJs) to terahertz (THz) electromagnetic (EM) irradiation. A significant amplification of the EM wave can be achieved by the IJJs stack when the incident frequency equals to one of the cavity frequencies. The irradiation excites pi phase kinks in the junctions, which stimulate the cavity resonance when the bias voltage is tuned. A large amount of dc energy is then pumped into the Josephson plasma oscillation, and the incident wave gets amplified. From the profound current step in IV characteristics induced at the cavity r…
We predict a new branch of surface Josephson plasma waves (SJPWs) in layered superconductors for frequencies higher than the Josephson plasma frequency. In this frequency range, the permittivity tensor components along and transverse to the layers have different signs, which is usually associated with negative refraction. However, for these frequencies, the bulk Josephson plasma waves cannot be matched with the incident and reflected waves in the vacuum, and, instead of the negative-refractive properties, abnormal surface modes appear within the frequency band expected for bulk modes. We also …
Theory of Coherent $c$-Axis Josephson Tunneling between Layered Superconductors
我们精确计算了两个层状超导体之间的$c$轴相干隧穿的约瑟夫森电流，每个层状超导体都具有内部相干紧束缚的层内和层间准粒子色散。我们的结果也适用于当一个或两个超导体是一种散装材料，并包括通常被忽视的表面状态的影响。对于弱隧穿，我们的结果减少到我们以前的结果使用隧穿哈密顿量。我们的结果对于强隧穿也是正确的。然而，$c$轴隧穿田中和柏屋的结果被证明是不正确的任何限制。此外，我们考虑了两个相同的层状超导体之间的$c$轴相干临界电流扭转一个角度$ϕ_0$关于$c$轴相对于彼此。不考虑序参量对称性，我们使用紧束缚层内准粒子色散的相干隧穿结果与最近的$c$轴扭曲双晶Bi $_2$ Sr $_2$ CaCu $_2$ O $_{8+δ}$ Li扭曲结实验不一致{ \it et al.}
We report numerical simulations of the nonlinear dynamics of Josephson vortices driven by strong dc currents in layered superconductors. Dynamic equations for interlayer phase differences in a stack of coupled superconducting layers were solved to calculate a drag coefficient $η(J)$ of the vortex as a function of the perpendicular dc current density $J$. It is shown that Cherenkov radiation produced by a moving vortex causes significant radiation drag increasing $η(v)$ at high vortex velocities $v$ and striking instabilities of driven Josephson vortices moving faster than a terminal velocity $…
