arXiv subjects

Arushi

Publications and source records attributed to Arushi.

28 records · Page 2Linked to original sources

arXiv2021

Superconducting and normal state properties of high entropy alloy Nb-Re-Hf-Zr-Tiinvestigated by muon spin relaxation and rotation

Superconducting high entropy alloy (HEA) are emerging as a new class of superconducting materials. It provides a unique opportunity to understand the complex interplay of disorder and superconductivity. We report the synthesis and detail bulk and microscopic characterization of Nb$_{60}$Re$_{10}$Zr$_{10}$Hf$_{10}$Ti$_{10}$ HEA alloy using transport, magnetization, specific heat, and muon spin rotation/relaxation ($μ$SR) measurements. Bulk superconductivity with transition temperature $T_{C}$ = 5.7 K confirmed by magnetization, resistivity, and heat capacity measurements. Zero-field $μ$SR measurement shows that the superconducting state preserves time-reversal symmetry, and transverse-field measurements of the superfluid density are well described by an isotropic s-wave model.

cond-mat.supr-con↗

arXiv2021

Probing the superconducting ground state of noncentrosymmetric high entropy alloys using muon-spin rotation and relaxation

Recently, high entropy alloys (HEAs) have emerged as a new platform for discovering superconducting materials and offer avenues to explore exotic superconductivity. The highly disordered nature of HEA suggests regular phonon required for BCS superconductivity may be unlikely to occur. Therefore understanding the microscopic properties of these superconducting HEA is important. We report the first detailed characterization of the superconducting properties of the noncentrosymmetric ($α$-Mn structure) HEA {(HfNb)}$_{0.10}${(MoReRu)}$_{0.90}$, and {(ZrNb)}$_{0.10}${(MoReRu)}$_{0.90}$ by using magnetization, specific heat, AC transport, and muon-spin relaxation/rotation ($μ$SR). Despite the disordered nature, low temperature specific heat and transverse-field muon spin rotation measurements suggest nodeless isotropic superconducting gap and Zero-field $μ$SR measurements confirm that time reversal symmetry is preserved in the superconducting ground state.

cond-mat.supr-con↗

arXiv2021

Microscopic investigation of superconducting properties of a strongly coupledsuperconductor IrGe via μSR

Exploring superconductors which can possess pairing mechanism other than the BCS predicted s-wave have continually attracted considerable interest. Superconductors with low-lying phonons may exhibit unconventional superconductivity as the coupling of electrons with these low-lying phonons can potentially affect the nature of the superconducting ground state, resulting in strongly coupled superconductivity. In this work, by using magnetization, AC transport, specific heat, and muon spin rotation/relaxation ($μ$SR) measurements, we report a detailed investigation on the superconducting ground state of the strongly coupled superconductor, IrGe, that has a transition temperature, T$_{C}$, at 4.7 K. Specific heat (SH), and transverse field $μ$SR is best described with an isotropic s-wave model with strong electron-phonon coupling, indicated by the values of both $Δ(0)/k_{B}T_{C}$ = 2.3, 2.1 (SH, $μ$SR), and $ΔC_{el}/γ_{n}T_{C}$ = 2.7. Zero-field $μ$SR measurements confirm the presence of time-reversal symmetry in the superconducting state of IrGe.

cond-mat.supr-con↗

arXiv2021

An investigation of type-I superconductivity in single crystal of Pb2Pd

We have investigated the superconducting properties in a single crystal of a new superconductor Pb$_{2}$Pd via various techniques including magnetization, AC transport, transverse field muon spin rotation and relaxation (TF-$μ$SR), and heat capacity. Pb$_{2}$Pd crystallizes in a body-centred tetragonal structure with space group I4/$mcm$. All measurements confirm the superconducting transition temperature, T$_{C}$ = 3.0 $\pm$ 0.1 K. Electronic specific heat data are well described by the BCS fitting, suggesting that Pb$_{2}$Pd opens an isotropic gap on entering the superconducting state. The specific heat jump and $λ_{e-ph}$ value categorize Pb$_{2}$Pd as a moderately coupled superconductor. Magnetization and transverse field muon spin rotation measurements along with Ginzburg-Landau parameter, $κ$ < 1/$\sqrt{2}$ strongly infers that Pb$_{2}$Pd is a type I superconductor.

cond-mat.supr-con↗

arXiv2021

Fully gapped superconductivity in centrosymmetric and non-centrosymmetric Re-B compounds probed with $μ$SR

We present a comprehensive study on superconducting properties of Re$_7$B$_3$ and Re$_3$B through specific heat, magnetic susceptibility, resistivity, and transverse and zero-field muon spin rotation/relaxation ($μ$SR) experiments on polycrystalline samples. Re$_7$B$_3$ (T$_C$ = 3.2~K) is a non-centrosymmetric type-II ($κ$ $\approx$ 9.27) superconductor in the weak coupling ($λ_{e-ph}$ = 0.54) regime. On the other hand, Re$_3$B (T$_C$ = 5.19~K) is a centrosymmetric type-II ($κ$ $\approx$ 34.55) superconductor in the moderate coupling ($λ_{e-ph}$ = 0.64) regime. Our transverse-field $μ$SR measurements show evidence for isotropically gapped BCS type superconductivity with normalized gap ($Δ_0/k_BT_C$) values of 1.69 (Re$_7$B$_3$) and 1.75 (Re$_3$B).

cond-mat.supr-con↗

arXiv2021

Spectroscopic evidence of mixed angular momentum symmetry in non-centrosymmetric Ru$_7$B$_3$

Superconducting crystals with lack of inversion symmetry can potentially host unconventional pairing. However, till date, no direct conclusive experimental evidence of such unconventional order parameters in non-centrosymmetric superconductors has been reported. In this paper, through direct measurement of the superconducting energy gap by scanning tunnelling spectroscopy, we report the existence of both $s$-wave (singlet) and $p$-wave (triplet) pairing symmetries in non-centrosymmetric Ru$_7$B$_3$. Our temperature and magnetic field dependent studies also indicate that the relative amplitudes of the singlet and triplet components of the order parameter change differently with temperature.

cond-mat.supr-con↗

arXiv2020

Time-reversal symmetry breaking and multigap superconductivity in the noncentrosymmetric superconductor La$_{7}$Ni$_{3}$

The Th$_{7}$Fe$_{3}$ family of superconductors provides a rich playground for unconventional superconductivity. La$_7$Ni$_3$ is the latest member of this family, which we here investigate by means of thermodynamic and muon spin rotation and relaxation measurements. Our specific heat data provides evidence for two distinct and approximately isotropic superconducting gaps. The larger gap has a value slightly higher than that of weak-coupling BCS theory, indicating the presence of significant correlations. These observations are confirmed by transverse-field muon-rotation measurements. Furthermore, zero-field measurements reveal small internal fields in the superconducting state, which occur close to the onset of superconductivity and indicate that the superconducting order parameter breaks time-reversal symmetry. We discuss two possible microscopic scenarios -- an unconventional $E_{2}(1,i)$ state and an $s+i\,s$ superconductor, which is reached by two consecutive transitions -- and illustrate which interactions will favor these phases. Our results establish La$_{7}$Ni$_{3}$ as the first member of the Th$_{7}$Fe$_{3}$ family displaying both time-reversal-symmetry-breaking and multigap superconductivity.

cond-mat.supr-con↗

arXiv2020

A Machine Learning Application for Raising WASH Awareness in the Times of COVID-19 Pandemic

Background: The COVID-19 pandemic has uncovered the potential of digital misinformation in shaping the health of nations. The deluge of unverified information that spreads faster than the epidemic itself is an unprecedented phenomenon that has put millions of lives in danger. Mitigating this Infodemic requires strong health messaging systems that are engaging, vernacular, scalable, effective and continuously learn the new patterns of misinformation. Objective: We created WashKaro, a multi-pronged intervention for mitigating misinformation through conversational AI, machine translation and natural language processing. WashKaro provides the right information matched against WHO guidelines through AI, and delivers it in the right format in local languages. Methods: We theorize (i) an NLP based AI engine that could continuously incorporate user feedback to improve relevance of information, (ii) bite sized audio in the local language to improve penetrance in a country with skewed gender literacy ratios, and (iii) conversational but interactive AI engagement with users towards an increased health awareness in the community. Results: A total of 5026 people who downloaded the app during the study window, among those 1545 were active users. Our study shows that 3.4 times more females engaged with the App in Hindi as compared to males, the relevance of AI-filtered news content doubled within 45 days of continuous machine learning, and the prudence of integrated AI chatbot Satya increased thus proving the usefulness of an mHealth platform to mitigate health misinformation. Conclusion: We conclude that a multi-pronged machine learning application delivering vernacular bite-sized audios and conversational AI is an effective approach to mitigate health misinformation.

cs.CY↗

arXiv2020

Unconventional superconducting properties of noncentrosymmetric Re5.5Ta

Rhenium based noncentrosymmetric superconductors crystallizing in $α$-Mn structure have become potential candidates to exhibit an unconventional superconducting ground-state. Here we report a detailed investigation on the superconducting and normal state properties of Re$_{5.5}$Ta, that also has the $α$-Mn structure. Magnetization, specific heat, and transport measurements confirm the bulk superconducting transition \textit{T}$_{C}$ at 8.0 K. Upper critical field value (H$_{C2}$(0)) calculated from magnetization, specific heat and AC transport measurements exceed the Pauli paramagnetic limit (14.7 T), indicating that the superconducting properties of Re$_{5.5}$Ta are probably unconventional in nature. However, low-temperature specific heat and transverse-field muon spin rotation measurements suggest a surprising nodeless isotropic superconducting gap, although with strong electron-phonon coupling.

cond-mat.supr-con↗

arXiv2018

Enhancement of the superconducting transition temperature by Re doping in Weyl semimetal MoTe$_{2}$

This work presents the emergence of superconductivity in Re substituted topological Weyl semimetal MoTe$_{2}$. Re substitution for Mo sites lead to a sizable enhancement in the superconducting transition temperature (T$_{c}$). A record high T$_{c}$ at ambient pressure in a 1T$'$-MoTe$_{2}$ (room temperature structure) related sample is observed for the Mo$_{0.7}$Re$_{0.3}$Te$_{2}$ composition (T$_{c}$ = 4.1 K, in comparison MoTe$_{2}$, shows a T$_{c}$ of 0.1 K). The experimental and theoretical studies indicate that Re substitution is doping electrons and facilitates the emergence of superconductivity by enhancing the electron-phonon coupling and density of states at the Fermi level. Our findings, therefore, open a new way to further manipulate and enhance the superconducting state together with the topological states in 2D van der Waals materials.

cond-mat.supr-con↗