arXiv subjects

Biswajit Dutta

Publications and source records attributed to Biswajit Dutta.

7 recordsLinked to original sources

arXiv2026

Universal route towards field-free electrically polarity-reversible Josephson diode

The realisation of superconducting diodes that operate without external magnetic fields and allow electrical control of polarity is a key goal for the integration of nonreciprocal elements into cryogenic and quantum technologies. Here, we demonstrate a universal and scalable approach to achieving such field-free and electrically reconfigurable Josephson diode functionality. Our method relies on long Josephson junctions with ferromagnetic barriers and asymmetric current injection - a configuration that inherently breaks both time-reversal and inversion symmetries. We show that the diode polarity is set by an applied bias current and can be reversed using short current pulses, without the need for magnetic fields or thermal cycling. The effect is robust, material-agnostic, and compatible with standard established fabrication processes. Our results provide a practical platform for integrating low-dissipation, programmable diodes into superconducting and quantum electronic circuits

cond-mat.supr-con↗

arXiv2025

In-Situ Manipulation of Superconducting Properties via Ultrasonic Excitation

We demonstrate in-situ manipulation of the critical temperature ($T_S$) and upper critical field ($H_{C2}$) of conventional and unconventional superconductors via ultrasonic excitation. Using an AC susceptibility measurements, we observed a reduction in $T_S$ with increasing amplitude of the applied ultrasonic waves. This reduction exhibits a power law dependence on the excitation voltage, suggesting a non-linear coupling between the ultrasonic waves and the superconducting order parameter. Analogous behavior was observed in cuprate superconductors, hinting at a possible link between the modified superconducting properties and the modulation of the antiferromagnetic network by ultrasonic excitation. Measurements on a paramagnetic material (Gd$_2$O$_3$) with quenched orbital angular momentum (L\,=\,0) revealed no change in magnetization even at extreme ultrasonic excitation amplitudes. This highlights the role of spin-orbit coupling in the observed effects and rules out the possibility of local temperature increases affecting the measurements. To further confirm this, we conducted auxiliary experiments where a Cernox temperature sensor was subjected to ultrasonic excitation, and the resulting temperature difference relative to a reference Cernox was recorded. Simultaneously, the power difference was measured to assess the impact of ultrasonic heating. This analysis revealed that localized heating effects become dominant above an ultrasonic amplitude of 10 V$_{pp}$.

cond-mat.supr-con↗

arXiv2024

A novel reentrant susceptibility due to vortex and magnetic dipole interaction in a La1.85Sr0.15CuO4 and Gd2O3 composite system

A reentrant behavior of temperature dependent magnetic ac-susceptibility (or excess susceptibility(ES)) at lower temperature is observed in a composite made of superconductor $La_{1.85}Sr_{0.15}CuO_4$ (LCu) and an insulating paramagnetic salt $Gd_2O_3$ (GdO). The ES exhibits an exponential characteristic that varies with temperature ($\exp,[\frac{T_0}{T}]$), T0 is characteristics temperature. The characteristics temperature,T$_0$, decreases as the effective interface diminishes and the amplitude of the dc magnetic field increases. The creation of ferromagnetic dimers between Gd$^{+3}$ ions in GdO is observed as a result of vortex-dipole interaction, which causes the observation of this unusual ES at temperatures much lower than the superconducting onset temperature T$_{S}^{onset}$. This type of ferromagnetic dimer formation much below superconducting transition temperature is found comparable with the formation of Yu-Shiba-Rusinov (YSR) state and interaction between these YSR state.

cond-mat.str-el↗

arXiv2023

Superconductivity controlled bulk magnetism

Ferromagnetism's ability to influence superconducting order is well known and well established, but the converse phenomena remains relatively less explored. Theoretical work on the subject includes Anderson and Suhl prediction of a crypto-ferromagnetic state, and De Gennes proposal of two ferromagnetic insulators exchange coupled through a superconductor. In this study, we present compelling evidence of coexistence of both phenomena in a superconducting spin valve system. We demonstrate that superconducting exchange coupling enables reliable bistable states, and the coexistence of SEC and CFM leads to a wide range of reproducible zero field micro-magnetic states in the SSV, which are a function of the strength of the superconducting state. These micromagnetic states can in turn influence the superconducting state, leading to multiple reproducible and non-volatile resistance states; thus paving the way for a novel direction in cryogenic in-memory computing.

cond-mat.supr-con↗

arXiv2023

Large tuneable exchange fields due to purely paramagnetically limited domain wall superconductivity

The ability to locally apply and tune large magnetic fields is a crucial requirement for several devices, most notably for detection and generation of majorana fermions. Such a functionality can be achieved in Superconductor (S) /Ferromagnet (F) bilayers, where superconductivity is strengthened on top of domain walls due to local lowering of the proximity induced effective exchange fields. This is predicted to result in significant superconducting Tc enhancements and possible complete magnetic controlled switching on and off of the superconducting state. By using thin films of superconducting Nb and ferromagnetic insulating (GdN) bilayers, and through detailed magneto-transport measurements, we demonstrate the previously unobserved phenomena of complete switching in and out of the S state in S/F bilayers. In the thinnest of Nb layers, we estimate that the domain wall state induced tunability of proximity induced exchange fields can be as high as 1.3T with application of in plane external fields of only a few mT.

cond-mat.supr-con↗

arXiv2022

Ferromagnetic exchange field stabilized antiferromagnetic ordering in a cuprate superconductor

We report experimental evidence of formation of antiferromagnetic clusters in composites made of a cuprate superconductor La1.85Sr0.15CuO4 (LCu) and a ferromagnet La0.6Sr0.4CoO3 (LCo). From linear and non-linear ac-susceptibility measurement on this composite material it is found that the exchange field of LCo suppress the dynamic antiferromagnetic spin fluctuation of LCu and convert it into the short range ordered superparamagnetic type antiferromagnetic (AFM) clusters at the cost of superconducting volume fraction. These shrank superconducting volume fraction shows quantum size effect (QSE) and follows DeGennes-Tinkham theory on finite size effect of superconductor.

cond-mat.supr-con↗

arXiv2011

Full-Rate Full-Diversity Achieving MIMO Precoding with Partial CSIT

In this paper, we consider a $n_t\times n_r$ multiple-input multiple-output (MIMO) channel subjected to block fading. Reliability (in terms of achieved diversity order) and rate (in number of symbols transmitted per channel use) are of interest in such channels. We propose a new precoding scheme which achieves both full diversity ($n_tn_r$th order diversity) as well as full rate ($n_t$ symbols per channel use) using partial channel state information at the transmitter (CSIT), applicable in MIMO systems including $n_r<n_t$ asymmetric MIMO. The proposed scheme achieves full diversity and improved coding gain through an optimization over the choice of constellation sets. The optimization maximizes $d_{min}^2$ for our precoding scheme subject to an energy constraint. The scheme requires feedback of $n_t-1$ angle parameter values, compared to $2n_tn_r$ real coefficients in case of full CSIT. Error rate performance results for $3\times 1$, $3\times 2$, $4\times 1$, $8\times 1$ precoded MIMO systems (with $n_t=3,3,4,8$ symbols per channel use, respectively) show that the proposed precoding achieves 3rd, 6th, 4th and 8th order diversities, respectively. These performances are shown to be better than other precoding schemes in the literature; the better performance is due to the choice of the signal sets and the feedback angles in the proposed scheme.

cs.IT↗