arXiv subjects

Sayak Bhowmik

Publications and source records attributed to Sayak Bhowmik.

5 recordsLinked to original sources

arXiv2026

Superconducting diode effect via Floquet topological Fulde-Ferrell phase in driven Rashba nanowire

Much has been studied on Floquet engineering in Rashba nanowire model regarding topological superconductivity hosting Majorana $0$- and anomalous $\pi$-modes, here we theoretically investigate the possible emergence of finite momentum Fulde-Ferrell (FF) superconducting state in quasi-energy of the above model under the periodic modulation of in-plane and out-of-plane magnetic fields while the static limit does not host a FF ground state. We demonstrate controllable switching between Floquet Majorana $0$- and $\pi$-modes via reversal of the supercurrent direction, revealing pronounced nonreciprocal supercurrent signatures which is a manifestation of the FF pairing. We validate the onset of FF pairing following a self-consistent mean-field analysis where externally applied supercurrent facilitates nonreciprocal signatures in quasi-energy spectra. The above findings directly indicates to the intriguing phenomenon of superconducting diode effect (SDE). The drive amplitude serves as a parameter to regulate the diode efficiency with chemical potential. Our study thus reveals a rich interplay between Floquet topological superconductivity and finite-momentum FF pairing, providing a tunable way to switch between different Floquet Majorana modes and realize the SDE with high efficiency.

cond-mat.mes-hall↗

arXiv2025

Field-free superconducting diode effect in two-dimensional Shiba lattices

The superconducting diode effect (SDE) refers to non-reciprocal transport, where current flows without resistance in one direction but becomes resistive in the opposite direction, but its typical reliance on magnetic field hinders scalability and device integration. In this article, we present a theoretical framework for realizing a field-free SDE based on a two-dimensional (2D) Shiba lattice featuring a conical spin texture. Using the real-space Bogoliubov-de Gennes (BdG) calculations, we illustrate that the conical spin configuration alone is sufficient to break the necessary inversion and time reversal symmetries, enabling nonreciprocal supercurrent flow without any external magnetic field, yielding diode efficiency exceeding 40%. Furthermore, we find that the efficiency of such a diode effect becomes strongly dependent on the direction of current flow, revealing a pronounced angular dependence that can be tuned by varying the pitches of the spin texture along the two spatial lattice directions. Our findings offer a pathway toward scalable, field-free superconducting components for non-dissipative electronics and quantum technologies.

cond-mat.supr-con↗

arXiv2025

Topological Majorana zero modes and the superconducting diode effect driven by Fulde-Ferrell-Larkin-Ovchinnikov pairing in a helical Shiba chain

We propose a theoretical framework for the realization of Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) pairing in a helical Shiba chain subjected to an out-of-plane Zeeman field, analyzed through a self-consistent Bogoliubov-de-Gennes (BdG) mean-field formalism approach. A chain of magnetic adatoms with helical spin texture deposited on the surface of a common $s$-wave superconductor, has emerged as a pivotal platform for realizing topological Majorana zero modes (MZMs). Our study reveals the crucial role of finite momentum pairing of Cooper pairs in the form of FFLO state which also supports topological MZMs at the ends of the chain. Interestingly, we demonstrate that FFLO pairing facilitates non-reciprocal charge transport, giving rise to superconducting diode effect in our system where both time-reversal and inversion symmetries are broken. Such diode effect stems directly from the presence of finite Cooper pair momentum of the FFLO ground state. Our comprehensive analysis highlights the intricate interplay between the richness of helical Shiba chain, the out-of-plane Zeeman field, and FFLO pairing in the emergence of MZMs and driving the superconducting diode effect. These findings offer valuable insights into the design and realization of topological superconducting devices with diode-like properties, potentially advancing technological applications in quantum computing and superconducting electronics.

cond-mat.supr-con↗

arXiv2024

Optimizing one dimensional superconducting diodes: Interplay of Rashba spin-orbit coupling and magnetic fields

The superconducting diode effect (SDE) refers to the non-reciprocal nature of the critical current (maximum current that a superconductor can withstand before turning into a normal metal) of a superconducting device. Here, we investigate SDE in helical superconductors with broken inversion and time-reversal symmetry, focusing on a prototypical Rashba nanowire device proximitized by an s-wave superconductor and subjected to external magnetic fields. Using a self-consistent Bogoliubov-de Gennes mean-field formalism, we analyze the interplay between linear and higher-order spin-orbit coupling (SOC), bulk supercurrents, and external magnetic fields. Our results demonstrate that Rashba nanowires with only linear SOC can achieve incredibly large diode efficiencies > 45% through the interplay of longitudinal and transverse magnetic fields. Notably, higher-order SOC introduces qualitatively different behavior, enabling finite diode efficiency even in the absence of a longitudinal Zeeman field due to inherent energy dispersion asymmetry. We present a comprehensive phase diagram of the device elucidating the emergent Fulde-Ferrell-Larkin-Ovchinnikov (FFLO) superconducting state and demonstrate that proximitized Rashba nanowires offer a versatile, practical platform for SDE, with potential realizations in existing material systems. These results provide crucial insights for optimizing SDE in nanoscale superconducting devices, paving the way for next-generation dissipationless quantum electronics.

cond-mat.supr-con↗

arXiv2024

Higher-order topological corner and bond-localized modes in magnonic insulators

We theoretically investigate a two-dimensional decorated honeycomb lattice framework to realize a second-order topological magnon insulator (SOTMI) phase featuring distinct corner-localized modes. Our study emphasizes the pivotal role of spin-magnon mapping in characterizing bosonic topological properties, which exhibit differences from their fermionic counterparts. We employ a symmetry indicator topological invariant to identify and characterize this SOTMI phase, particularly for systems respecting time-reversal and ${\sf{C}}_6$ rotational symmetry. Using a spin model defined on a honeycomb lattice geometry, we demonstrate that introducing ``\textit{kekulé}'' type distortions yields a topological phase. In contrast, ``\textit{anti-kekulé}'' distortions result in a non-topological magnonic phase. The presence of kekulé distortions manifests in two distinct topologically protected bosonic corner modes - an \textit{intrinsic} and a \textit{pseudo}, based on the specific edge terminations. On the other hand, anti-kekulé distortions give rise to \SW{\textit{Tamm/Shockley}} type bond-localized boundary modes, which are non-topological and reliant on particular edge termination. We further investigate the effects of random out-of-plane exchange anisotropy disorder on the robustness of these bosonic corner modes. The distinction between SOTMIs and their fermionic counterparts arises due to the system-specific magnonic onsite energies, a crucial feature often overlooked in prior literature. Our study unveils exciting prospects for engineering higher-order topological phases in magnon systems and enhances our understanding of their unique behavior within decorated honeycomb lattices.

cond-mat.mes-hall↗