arXiv subjects

Lovy Sharma

Publications and source records attributed to Lovy Sharma.

3 recordsLinked to original sources

arXiv2026

Phase-controlled perfect nonlocal spin and charge diode effects in a four-terminal Josephson junction with $p$-wave magnets

We theoretically investigate charge and spin transport in a four-terminal Josephson junction with a normal-metal barrier. The top and bottom superconducting leads are equal-spin triplet $p_y$-wave superconductors, while the left and right leads are $p$-wave magnets with proximity-induced conventional $s$-wave superconductivity. When the transverse macroscopic phase difference between the top and bottom leads is set to zero, a longitudinal phase bias generates a pure transverse spin current with perfect 100% nonreciprocity. Remarkably, a finite transverse phase difference preserves the perfect spin-diode effect while simultaneously inducing a perfect charge-diode effect, enabling fully nonreciprocal spin and charge transport. Moreover, the spin-diode efficiency exhibits sharp, step-like switching as a function of both the gate voltage applied to the barrier and the crystallographic orientation of the $p$-wave magnet, providing independent and experimentally accessible knobs for controlling the diode polarity. The diode response remains robust against asymmetric interface couplings, nonmagnetic disorder, variations in the relative singlet and triplet pairing strengths, temperature, and junction dimensions, demonstrating that the effect is not a consequence of fine-tuned parameters. These findings establish the proposed four-terminal junction as a highly tunable and structurally robust platform for dissipationless, phase-controlled spin and charge rectification, with potential applications in superconducting spintronics.

cond-mat.supr-con↗

arXiv2026

$p$-wave magnet driven field-free Josephson diode effect

Recently, the superconducting diode effect (SDE), characterized by unequal critical currents in opposite directions, has been observed experimentally and predicted theoretically in models of bulk superconductors and Josephson junctions (JJs). In this work, we construct a Josephson junction using a recently discovered unconventional coplanar magnet, the $p$-wave magnet (PM), with proximity-induced superconductivity, and demonstrate the emergence of a Josephson diode effect (JDE). The barrier region is formed by another unconventional collinear magnet, namely an altermagnet (AM). We illustrate that apart from time-reversal and inversion symmetries, the mirror operation $M_{yz}$ emerges as the key symmetry constraint. Also, unlike earlier models that realize the JDE using unconventional magnets, this setup does not require Rashba spin-orbit coupling (SOC) or different superconductors across the junction. Moreover, we demonstrate that the realization of the JDE in this framework requires only minimal conditions while maintaining high performance. The effect remains robust across a broad parameter regime, and thus making the system particularly promising for applications in quantum circuits and computing technologies.

cond-mat.supr-con↗

arXiv2025

Tunable Josephson diode effect in singlet superconductor-altermagnet-triplet superconductor junctions

Recently discovered phase of collinear magnet called, altermagnet breaks time reversal symmetry (TRS), exhibits momentum-dependent spin-splitting of band structure with zero net magnetization. In this work, we theoretically investigate the Josephson junction (JJ) of spin singlet superconductor (SC)/altermagnet/spin triplet SC and demonstrate that it manifests field free Josephson diode effect (JDE). We illustrate that there are four key requisites to have JDE in such JJs, namely, broken TRS, left and right SC in the JJ shall be non-identical, presence of spin orbit interaction, and anisotropy in spin polarization at the Fermi surface or anisotropy in pair potential of the SC. It has also been shown that by applying a gate potential in the altermagnetic regime, one can not only reverse the sign of efficiency but also modulate its magnitude. Our system can be used as a superconducting rectifier that can be tuned efficiently using gate voltage and system parameters without having external magnetic field.

cond-mat.mes-hall↗