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Intrinsic Non-linearity of Josephson Junctions as an Alternative Origin of the Missing First Shapiro Step
Authors:
Lei Xu,
Shuhang Mai,
Manzhang Xu,
Xue Yang,
Lihong Hu,
Xinyi Zheng,
Sicheng Zhou,
Siyuan Zhou,
Bingbing Tong,
Xiaohui Song,
Jie Shen,
Zhaozheng Lyu,
Ziwei Dou,
Xiunian Jing,
Fanming Qu,
Peiling Li,
Guangtong Liu,
Li Lu
Abstract:
The missing first Shapiro step in microwave-irradiated Josephson junctions has been widely interpreted as a hallmark of Majorana bound states. However, conventional mechanisms like junction underdamping or Joule heating can produce similar signatures. Here, we demonstrate that the intrinsic non-linear current-voltage characteristic of low-to-moderate transparency junctions can also suppress the fi…
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The missing first Shapiro step in microwave-irradiated Josephson junctions has been widely interpreted as a hallmark of Majorana bound states. However, conventional mechanisms like junction underdamping or Joule heating can produce similar signatures. Here, we demonstrate that the intrinsic non-linear current-voltage characteristic of low-to-moderate transparency junctions can also suppress the first step, accompanied by distinctive zigzag boundaries between the zeroth and first step at intermediate driving frequencies. Microwave measurements on Al/WTe2 junctions and numerical simulations of a non-linear resistively and capacitively shunted junction model reveal the first step collapse induced by switching jumps of current, together with zigzag features absent in scenarios solely driven by finite \b{eta} or Joule heating. This zigzag signature therefore provides a crucial diagnostic tool, emphasizing the necessity of comprehensive analysis of microwave spectra before attributing the absence of the first Shapiro step to Majorana physics.
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Submitted 22 October, 2025;
originally announced October 2025.
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Stationary Josephson effect in a short multi-terminal junction
Authors:
Sebastian Mai,
Ervand Kandelaki,
Anatoly Volkov,
Konstantin Efetov
Abstract:
We study the dc Josephson effect and the density of states in a multiterminal structure of cross-type geometry which consists of four superconducting electrodes connected by one-dimensional normal or ferromagnetic wires. We find that the Josephson current $I_{Jz}$ has a sinusoidal dependence on the phase difference $φ_z$ between the superconductors in the horizontal wire with a critical current…
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We study the dc Josephson effect and the density of states in a multiterminal structure of cross-type geometry which consists of four superconducting electrodes connected by one-dimensional normal or ferromagnetic wires. We find that the Josephson current $I_{Jz}$ has a sinusoidal dependence on the phase difference $φ_z$ between the superconductors in the horizontal wire with a critical current $I_c$ that can be varied by changing the phase difference $φ_y$ between the superconductors in the vertical wire. The period of the function $I_{Jz}(φ_z)$ depends on the ratio of the interface resistances $R_{Sn,z}/R_{Sn,y}$ being equal to $2π$ if this ratio is small and equal to $4π$ in the opposite limit. We also calculate the amplitudes of both the singlet and the odd-frequency triplet component in the system under consideration. The triplet component amplitude may be significantly larger than the amplitude of the singlet component.
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Submitted 15 January, 2013; v1 submitted 23 October, 2012;
originally announced October 2012.
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Dynamical control of matter wave splitting using time-dependent optical lattices
Authors:
Sung Jong Park,
Henrik Kjaer Andersen,
Sune Mai,
Jan Arlt,
Jacob F. Sherson
Abstract:
We report on measurements of splitting Bose-Einstein condensates (BEC) by using a time-dependent optical lattice potential. First, we demonstrate the division of a BEC into a set of equally populated components by means of time dependent control of Landau-Zener tunneling in a vertical lattice potential. Next, we apply time dependent optical Bragg mirrors to a BEC oscillating in a harmonic trap. We…
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We report on measurements of splitting Bose-Einstein condensates (BEC) by using a time-dependent optical lattice potential. First, we demonstrate the division of a BEC into a set of equally populated components by means of time dependent control of Landau-Zener tunneling in a vertical lattice potential. Next, we apply time dependent optical Bragg mirrors to a BEC oscillating in a harmonic trap. We demonstrate high-order Bragg reflection of the condensate due to multi-photon Raman transitions, where the depth of the optical lattice potential allows for a choice of the order of the transition. Finally, a combination of multiple Bragg reflections and Landau-Zener tunneling allows for the generation of macroscopic arrays of condensates with potential applications in atom optics and atom interferometry.
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Submitted 29 March, 2012;
originally announced March 2012.
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Interaction of Josephson and magnetic oscillations in Josephson tunnel junctions with a ferromagnetic layer
Authors:
S. Mai,
E. Kandelaki,
A. F. Volkov,
K. B. Efetov
Abstract:
We study the dynamics of Josephson junctions with a thin ferromagnetic layer F [superconductor-ferromagnet-insulator-ferromagnet-superconductor (SFIFS) junctions]. In such junctions, the phase difference $φ$ of the superconductors and magnetization $M$ in the F layer are two dynamic parameters coupled to each other. We derive equations describing the dynamics of these two parameters and formulate…
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We study the dynamics of Josephson junctions with a thin ferromagnetic layer F [superconductor-ferromagnet-insulator-ferromagnet-superconductor (SFIFS) junctions]. In such junctions, the phase difference $φ$ of the superconductors and magnetization $M$ in the F layer are two dynamic parameters coupled to each other. We derive equations describing the dynamics of these two parameters and formulate the conditions of validity. The coupled Josephson plasma waves and oscillations of the magnetization $M$ affect the form of the current-voltage ($I$-$V$) characteristics in the presence of a weak magnetic field (Fiske steps). We calculate the modified Fiske steps and show that the magnetic degree of freedom not only changes the form of the Fiske steps but also the overall view of the $I$-$V$ curve (new peaks related to the magnetic resonance appear). The $I$-$V$ characteristics are shown for different lengths of the junction including those which correspond to the current experimental situation. We also calculate the power $P$ absorbed in the system if a microwave radiation with an ac in-plane magnetic field is applied (magnetic resonance). The derived formula for the power $P$ essentially differs from the one which describes the power absorption in an isolated ferromagnetic film. In particular, this formula describes the peaks related to the excitation of standing plasma waves as well as the peak associated with the magnetic resonance.
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Submitted 27 October, 2011; v1 submitted 22 July, 2011;
originally announced July 2011.
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Pump-probe coupling of matter wave packets to remote lattice states
Authors:
Jacob F. Sherson,
Sung Jong Park,
Poul Pedersen,
Nils Winter,
Miroslav Gajdacz,
Sune Mai,
Jan Arlt
Abstract:
The coherent manipulation of wave packets is an important tool in many areas of physics. We demonstrate the experimental realization of quasi-free wave packets of ultra-cold atoms bound by an external harmonic trap. The wave packets are produced by modulating the intensity of an optical lattice containing a Bose-Einstein condensate. The evolution of these wave packets is monitored in-situ and thei…
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The coherent manipulation of wave packets is an important tool in many areas of physics. We demonstrate the experimental realization of quasi-free wave packets of ultra-cold atoms bound by an external harmonic trap. The wave packets are produced by modulating the intensity of an optical lattice containing a Bose-Einstein condensate. The evolution of these wave packets is monitored in-situ and their reflection on a band gap is observed. In direct analogy with pump-probe spectroscopy, a probe pulse allows for the resonant de-excitation of the wave packet into localized lattice states at a long, controllable distance of more than 100 lattice sites from the main component. This coherent control mechanism for ultra-cold atoms thus enables controlled quantum state preparation, opening exciting perspectives for quantum metrology and simulation.
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Submitted 8 July, 2011;
originally announced July 2011.
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Photocurrent in a visible-light graphene photodiode
Authors:
S. Mai,
S. V. Syzranov,
K. B. Efetov
Abstract:
We calculate the photocurrent in a clean graphene sample normally irradiated by a monochromatic electromagnetic field and subject to a step-like electrostatic potential. We consider the photon energies $\hbarΩ$ that significantly exceed the height of the potential barrier, as is the case in the recent experiments with graphene-based photodetectors. The photocurrent comes from the resonant absorpti…
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We calculate the photocurrent in a clean graphene sample normally irradiated by a monochromatic electromagnetic field and subject to a step-like electrostatic potential. We consider the photon energies $\hbarΩ$ that significantly exceed the height of the potential barrier, as is the case in the recent experiments with graphene-based photodetectors. The photocurrent comes from the resonant absorption of photons by electrons and decreases with increasing ratio $\hbarΩ/U_0$. It is weakly affected by the background gate voltage and depends on the light polarization as $\propto\sin^2γ$, $γ$ being the angle between the potential and the polarization plane.
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Submitted 3 February, 2011; v1 submitted 18 October, 2010;
originally announced October 2010.
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Mixing of ultracold atomic clouds by merging of two magnetic traps
Authors:
Jesper Fevre Bertelsen,
Henrik Kjaer Andersen,
Sune Mai,
Michael Budde
Abstract:
We demonstrate a method to make mixtures of ultracold atoms that does not make use of a two-species magneto-optical trap. We prepare two clouds of 87Rb atoms in distinct magnetic quadrupole traps and mix the two clouds by merging the traps. For correctly chosen parameters the mixing can be done essentially without loss of atoms and with only minor heating. The basic features of the process can b…
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We demonstrate a method to make mixtures of ultracold atoms that does not make use of a two-species magneto-optical trap. We prepare two clouds of 87Rb atoms in distinct magnetic quadrupole traps and mix the two clouds by merging the traps. For correctly chosen parameters the mixing can be done essentially without loss of atoms and with only minor heating. The basic features of the process can be accounted for by a classical simulation of particle trajectories. Such calculations indicate that mixing of different mass species is also feasible, opening the way for using the method as a starting point for making quantum gas mixtures.
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Submitted 18 February, 2007; v1 submitted 15 June, 2006;
originally announced June 2006.