arXiv subjects

Taras Golod

Publications and source records attributed to Taras Golod.

9 recordsLinked to original sources

arXiv2026

In-situ tunable superconducting diode: towards field-free operation with infinite nonreciprocity

Efficient, scalable, and magnetic-field-free superconducting diodes are essential for future superconducting electronics; yet, despite significant efforts, such practical devices remain unrealized. The main challenge lies in achieving broad-range in-situ tunability, both for optimization and for achieving transistor-like operation. Here, we study diodes based on four-terminal niobium planar Josephson junctions. We show that the multiterminal structure eliminates the need for an external magnetic field and enables essentially unrestricted in-situ tunability, along with reconfigurability of the diode polarity, leading to new functionality. For example, we demonstrate that such diodes can operate as Gauss neurons via reentrant superconductivity. By deliberately tuning the junction parameters, we obtain effectively infinite nonreciprocity (within experimental resolution) leading to threshold-free ac-current rectification. Such technologically simple, reconfigurable, and broadly tunable diodes could be instrumental for future digital and neuromorphic computing.

physics.app-ph↗

arXiv2025

Demonstration of an optical microwave rectification by a superconducting diode with near 100% efficiency

Superconducting electronics offer significant advantages in speed and power efficiency for next-generation computing and communication systems. However, their practical deployment is limited by the absence of simple, efficient, and scalable superconducting counterparts to key semiconductor components. In this work, we investigate diodes based on planar Josephson junctions fabricated from a conventional niobium superconductor. The nonreciprocity in these diodes arises from the self-field effect induced by the geometrical asymmetry of the junction. By deliberate tuning of the junction parameters, we achieved effectively infinite nonreciprocity (within experimental resolution), characterized by a complete suppression of the superconducting critical current in one direction while maintaining a significant current in the opposite direction. The key novelty of this work lies in the demonstration of the optical diode effect. We observed threshold-free rectification of 75 GHz microwave radiation, indicating that these diodes exhibit near-ideal optical nonreciprocity. Our results open new avenues for ultrafast superconducting electronics and lay the groundwork for wireless sub-THz signal processing.

cond-mat.supr-con↗

arXiv2023

Word and bit line operation of a 1x1 μm2 superconducting vortex-based memory

The lack of dense random access memory is one of the main bottlenecks for the creation of a digital superconducting computer. In this work we study experimentally vortex-based superconducting memory cells. Three main results are obtained. First, we test scalability and demonstrate that the cells can be straightforwardly miniaturized to submicron sizes. Second, we emphasize the importance of conscious geometrical engineering. In the studied devices we introduce an asymmetric easy track for vortex motion and show that it enables a controllable manipulation of vortex states. Finally, we perform a detailed analysis of word and bit line operation of a 1x1 μm2 cell. High-endurance, nonvolatile operation at zero magnetic field is reported. Remarkably, we observe that the combined word and bit line threshold current is significantly reduced compared to the bare word-line operation. This could greatly improve the selectivity of individual cell addressing in a multibit RAM. The achieved one square micron area is an important milestone and a significant step forward towards creation of a dense cryogenic memory.

cond-mat.supr-con↗

arXiv2022

Holographic reconstruction of magnetic field distribution in a Josephson junction from diffraction-like Ic(H) patterns

A general problem of magnetic sensors is a trade-off between spatial resolution and magnetic field sensitivity. With decreasing sensor size its resolution is improved but the sensitivity is deteriorated. Obviation of such the trade-off requires development of super-resolution imaging technique, not limited by the sensor size. Here we present a proof of concept for a super-resolution method of magnetic imaging by a Josephson junction. It is based on a solution of an inverse problem - reconstruction of a local magnetic field distribution within a junction from the dependence of the critical current on an external magnetic field, Ic(H). The method resembles the Fourier-transform holography, with the diffraction-like Ic(H) pattern serving as a hologram. A simple inverse problem solution, valid for an arbitrary symmetric case, is derived. We verify the method numerically and show that the accuracy of reconstruction does not depend on the junction size and is only limited by the field range of the Ic(H) pattern. Finally, the method is tested experimentally using planar Nb Josephson junctions. Super-resolution reconstruction of stray magnetic fields from an Abrikosov vortex, trapped in the junction electrodes, is demonstrated. Thus, our method facilitate both the high field sensitivity and high spatial resolution, obviating the trade-off problem of magnetic sensors. We conclude that the holographic magnetic imaging by a planar Josephson junction can be used in scanning probe microscopy.

cond-mat.supr-con↗

arXiv2021

Accurate determination of the Josephson critical current by lock-in measurements

Operation of Josephson electronics usually requires determination of the Josephson critical current $I_c$, which is affected both by fluctuations and measurement noise. Lock-in measurements allow obviation of $1/f$ noise and, therefore, provide a major advantage in terms of noise and accuracy with respect to conventional dc-measurements. In this work we show both theoretically and experimentally that the $I_c$ can be accurately extracted using first and third harmonic lock-in measurements of junction resistance. We derive analytic expressions and verify them experimentally on nano-scale Nb-PtNi-Nb and Nb-CuNi-Nb Josephson junctions.

cond-mat.supr-con↗

arXiv2021

Transport characterization of magnetic states in Superconductor/Ferromagnet Nb/Co multilayers

Employment of the non-trivial proximity effect in Superconductor/Ferromagnet (S/F) heterostructures for creation of novel superconducting devices requires an accurate control of magnetic states in complex thin-film multilayers composing such devices. In this work we study experimentally in-plane transport properties of micro-structured Nb/Co multilayers. We apply various experimental techniques for characterization of multilayers, including the anisotropic magnetoresistance, the Hall effect and the first-order-reversal-curves analysis. We demonstrate that a combination of those techniques can provide a detailed knowledge of the magnetic state of the multilayer. In particular, we identify the range of existence of the coherently rotating, monodomain scissor-like state. It is anticipated, that in this noncollinear magnetic state the unconventional odd-frequency spin-triplet order parameter should appear. The non-hystertic nature of this state allows reversible tuning of the magnetic orientation. Thus, we identify the range of parameters and the procedure for controllable operation of devices based on such S/F heterostructures.

cond-mat.supr-con↗

arXiv2014

Controllable generation of a spin-triplet supercurrent in a Josephson spin-valve

It has been predicted theoretically that an unconventional odd-frequency spin-triplet component of superconducting order parameter can be induced in multilayered ferromagnetic structures with non-collinear magnetization. In this work we study experimentally nano-scale devices, in which a ferromagnetic spin valve is embedded into a Josephson junction. We demonstrate two ways of in-situ analysis of such Josephson spin valves: via magnetoresistance measurements and via in-situ magnetometry based on flux quantization in the junction. We observe that supercurrent through the device depends on the relative orientation of magnetization of the two ferromagnetic layers and is enhanced in the non-collinear state of the spin valve. This provides a direct prove of controllable generation of the spin-triplet superconducting component in a ferromagnet.

cond-mat.supr-con↗

arXiv2012

The anti-ordinary Hall effect in NiPt thin films

We study the anomalous Hall effect in binary alloys between the group-10 elements Ni and Pt. It is observed that the ordinary Hall effect is negative (electron-like) at any composition of the alloy. The extraordinary Hall effect is also negative except in the vicinity of the ferromagnetic quantum critical point. Close to the critical point the sign of the extraordinary Hall effect can be changed to positive (hole-like) by tuning either the temperature or the composition of the alloy. We attribute such an "anti-ordinary" Hall effect with opposite signs of the ordinary and the extraordinary contributions to a Berry phase singularity, moving away from the Fermi energy with increasing the ferromagnetic exchange energy.

cond-mat.mtrl-sci↗

arXiv2010

Detection of the phase shift from a single quantized superconducting vortex

An Abrikosov vortex in a superconductor carries a flux quantum, Phi_0 = hc/2e, localized at its center, but induces a global 2pi phase rotation in the superconducting condensate. This long-range gauge field outside the area pierced by a magnetic field is due to the Aharonov-Bohm effect, which is a non-classical phenomenon that illustrates the significance of potentials rather than forces in quantum mechanics. In the London gauge, the phase of the condensate is given by the polar angle around the vortex. Here we raise the question whether this phase shift could be detected by means of Cooper pair interferometry using Josephson junctions as phase-sensitive detectors. We introduce a single Abrikosov vortex into a superconducting lead with a detector junction made at the edge of the lead. We observe that the vortex induces a Josephson phase shift equal to the polar angle of the vortex within the junction length. When the vortex is close to the junction it induces a pi-step in the Josephson phase difference, leading to a controllable and reversible switching of the junction into the 0 - pi state. This in turn results in an unusual Phi_0/2 quantization of the flux in the junction. The vortex may hence act as a tunable "phase battery" for quantum electronics.

cond-mat.supr-con↗