arXiv subjects

A. Banerjee

Publications and source records attributed to A. Banerjee.

At least 37 records · Page 2Linked to original sources

arXiv2023

Beyond the 3rd moment: A practical study of using lensing convergence CDFs for cosmology with DES Y3

Widefield surveys of the sky probe many clustered scalar fields -- such as galaxy counts, lensing potential, gas pressure, etc. -- that are sensitive to different cosmological and astrophysical processes. Our ability to constrain such processes from these fields depends crucially on the statistics chosen to summarize the field. In this work, we explore the cumulative distribution function (CDF) at multiple scales as a summary of the galaxy lensing convergence field. Using a suite of N-body lightcone simulations, we show the CDFs' constraining power is modestly better than that of the 2nd and 3rd moments of the field, as they approximately capture the information from all moments of the field in a concise data vector. We then study the practical aspects of applying the CDFs to observational data, using the first three years of the Dark Energy Survey (DES Y3) data as an example, and compute the impact of different systematics on the CDFs. The contributions from the point spread function are 2-3 orders of magnitude below the cosmological signal, while those from reduced shear approximation contribute $\lesssim 1\%$ to the signal. Source clustering effects and baryon imprints contribute $1-10\%$. Enforcing scale cuts to limit systematics-driven biases in parameter constraints degrades these constraints a noticeable amount, and this degradation is similar for the CDFs and the moments. We also detect correlations between the observed convergence field and the shape noise field at $13σ$. We find that the non-Gaussian correlations in the noise field must be modeled accurately to use the CDFs, or other statistics sensitive to all moments, as a rigorous cosmology tool.

astro-ph.CO↗

arXiv2023

Magnetization, dielectric and thermal studies in the double perovskite polycrystalline compound Tm2CoMnO6

We report here a comprehensive study on structural, magnetic, caloric and electronic properties of the monoclinic phase of double perovskite compound Tm2CoMnO6 (TCMO) in its polycrysttaline format. Magnetic measurements confirm the presence of thermal hysteresis in magnetization indicates towards a first order magnetic transition at its critical point (Tc). Our study finds the metamagnetic jump in isothermal M(H) at 2 K that signifies the rare earth spin allignement in loop cycling above a certain critical field. This jump is only present at very low T that dies out as the T raises. M(H) measurements at different temperature stipulate that Co2+ and Mn4+ do not order completely inspite of strong ferromagnetic correlation that is against the previous study on TCMO. The concurrence of structral, magnetic and dielectric anomaly at Tc suggest its possible magnetostructural copuling. We found a high dielectric constant (2700) in TCMO and the Maxwell-Wagner electrial loss spectrum analysis hints towards a long range hopping mechanism. Sizeable magnetocaloric effect in terms of entropy change across the transition temperatures has been obtained from heat capacity data that clearly corroborates its intrinsic behaviour.

cond-mat.mtrl-sci↗

arXiv2023

Dynamic Asset Allocation with Expected Shortfall via Quantum Annealing

Recent advances in quantum hardware offer new approaches to solve various optimization problems that can be computationally expensive when classical algorithms are employed. We propose a hybrid quantum-classical algorithm to solve a dynamic asset allocation problem where a target return and a target risk metric (expected shortfall) are specified. We propose an iterative algorithm that treats the target return as a constraint in a Markowitz portfolio optimization model, and dynamically adjusts the target return to satisfy the targeted expected shortfall. The Markowitz optimization is formulated as a Quadratic Unconstrained Binary Optimization (QUBO) problem. The use of the expected shortfall risk metric enables the modeling of extreme market events. We compare the results from D-Wave's 2000Q and Advantage quantum annealers using real-world financial data. Both quantum annealers are able to generate portfolios with more than 80% of the return of the classical optimal solutions, while satisfying the expected shortfall. We observe that experiments on assets with higher correlations tend to perform better, which may help to design practical quantum applications in the near term.

quant-ph↗

arXiv2023

Non-equilibrium VLS-grown stable ST12-Ge thin film on Si substrate: A study on strain-induced band-engineering

The current work describes a novel method of growing thin films of stable crystalline ST12-Ge, a high pressure polymorph of Ge, on Si substrate by a non-equilibrium VLS-technique. The study explores the scheme of band engineering of ST12-Ge by inducing process-stress into it as a function of the growth temperature and film thickness. In the present work, ST12-Ge films are grown at 180 C - 250 C to obtain thicknesses of ~4.5-7.5 nm, which possess extremely good thermal stability up to a temperature of ~350 C. Micro-Raman study shows the stress induced in such ST12-Ge films to be compressive in nature and vary in the range of ~0.5-7.5 GPa. The measured direct band gap is observed to vary within 0.688 eV to 0.711 eV for such stresses, and four indirect band gaps are obtained to be 0.583 eV, 0.614-0.628 eV, 0.622-0.63 eV and 0.623-0.632 eV, accordingly. The corresponding band structures for unstrained and strained ST12-Ge are calculated by performing DFT simulation, which shows that a compressive stress transforms the fundamental band gap at M-G valley from indirect to direct one. Henceforth, the possible route of strain induced band engineering in ST12-Ge is explored by analyzing all the transitions in strained and unstrained band structures along with substantiation of the experimental results and theoretical calculations. The investigation shows that unstrained ST12-Ge is a natural n-type semiconductor which transforms into p-type upon incorporation of a compressive stress of ~5 GPa, with the in-plane electron effective mass components at M-G band edge to be ~0.09 me. Therefore, such band engineered ST12-Ge exhibits superior mobility along with its thermal stability and compatibility with Si, which can have potential applications to develop high-speed MOS devices for advanced CMOS technology.

cond-mat.mtrl-sci↗

arXiv2022

A New Type of Lattice Gauge Theory through Self-adjoint Extensions

A generalization of Wilsonian lattice gauge theory may be obtained by considering the possible self-adjoint extensions of the electric field operator in the Hamiltonian formalism. In the special case of 3D $\mathrm{U}(1)$ gauge theory these are parametrised by a phase $θ$, and the ordinary Wilson theory is recovered for $θ=0$. We consider the case $θ=π$, which, upon dualization, turns into a theory of staggered integer and half-integer height variables. We investigate order parameters for the breaking of the relevant symmetries, and thus study the phase diagram of the theory, which shows evidence of a broken $\mathbb{Z}_2$ symmetry in the continuum limit, in contrast to the ordinary theory.

hep-lat↗

arXiv2022

Early Release Science of the exoplanet WASP-39b with JWST NIRSpec PRISM

Transmission spectroscopy of exoplanets has revealed signatures of water vapor, aerosols, and alkali metals in a few dozen exoplanet atmospheres. However, these previous inferences with the Hubble and Spitzer Space Telescopes were hindered by the observations' relatively narrow wavelength range and spectral resolving power, which precluded the unambiguous identification of other chemical species$-$in particular the primary carbon-bearing molecules. Here we report a broad-wavelength 0.5-5.5 $μ$m atmospheric transmission spectrum of WASP-39 b, a 1200 K, roughly Saturn-mass, Jupiter-radius exoplanet, measured with JWST NIRSpec's PRISM mode as part of the JWST Transiting Exoplanet Community Early Release Science Team program. We robustly detect multiple chemical species at high significance, including Na (19$σ$), H$_2$O (33$σ$), CO$_2$ (28$σ$), and CO (7$σ$). The non-detection of CH$_4$, combined with a strong CO$_2$ feature, favours atmospheric models with a super-solar atmospheric metallicity. An unanticipated absorption feature at 4$μ$m is best explained by SO$_2$ (2.7$σ$), which could be a tracer of atmospheric photochemistry. These observations demonstrate JWST's sensitivity to a rich diversity of exoplanet compositions and chemical processes.

astro-ph.EP↗

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↗

arXiv2022

User Manual of Automatic Data Curation Tool(ADCT): A bulk data curator software in Library and Information Science

In library and information science, document storage and user-specific document retrieval are the main aspects of digital library services. To preserve the cultural heritage, documents, and literature, we need a common platform where all types of documents are available in a specific format. Our proposed software tool, ADCT can handle a bulk amount of data and transforms different types of raw data into specified metadata information. It generalizes multiple forms of curation logic applied to the source data. As state of the art, many research activities is done in various university to manage their research data in digital library services. The author provides descriptive statistics of library and information service (LIS) activities for information storage and retrieval. The paper shows research on methodology, information gathering, and scientific communication done on library data as an activity of the LIS community. The analysis of LIS data and the change of interest in information storage and retrieval from classification and indexing to retrieval are much important. For Building these types of digitized educational services, automatic data curation is an important stepping stone. The paper shows that automation can complement expertise and knowledge. The author builds an automated data transformation and curation tool that assists users in the analysis of metadata information and effort towards conforming to generic standards using a catalog when a librarian wants to see the adjacent related metadata for an archival collection of congressional correspondence.

cs.DL↗

arXiv2022

Chiral to Nematic Crossover in the Superconducting State of 4Hb-TaS$_2$

Most superconductors have an isotropic, single component order parameter, and are well described by the BCS theory for superconductivity. Unconventional, multiple components superconductors are exceptionally rare and are much less understood. Here, we combine scanning tunneling microscopy and angle-resolved macroscopic transport to study the candidate chiral superconductor, 4Hb-TaS$_2$. We reveal quasi-periodic one-dimensional modulations in the tunneling conductance accompanied by two-fold symmetric superconducting critical field. The strong modulation of the in-plane critical field, points to a nematic, unconventional order parameter. However, the imaged vortex core is nearly circular symmetric, suggesting an isotropic order parameter. We reconcile this apparent discrepancy by modeling a competition between a dominating chiral superconducting order parameter and a nematic one, the latter emerges close to the normal phase. Our results strongly support the existence of two-component superconductivity in 4Hb-TaS$_2$ and can provide useful insights to other systems with coexistent charge order and superconductivity.

cond-mat.supr-con↗

arXiv2022

On state dependent batch service queue with single and multiple vacation under Markovian arrival process

An infinite buffer batch service vacation queue has been studied where service rate of the batch is dependent on the size of the batch and vacation rate is dependent on the queue size at vacation initiation epoch. The arrivals follow the Markovian arrival process (MAP). For service rule, general bulk service (GBS) rule is considered. The service time and vacation time both are considered to be generally distributed. Several joint distributions of interest are obtained using the bivariate vector generating function method and the supplementary variable technique (SVT). Numerical results are presented to show the behavior of the system performance to validate the analytical results.

math.PR↗

arXiv2022

Multipartite Entanglement in Rabi Driven Superconducting Qubits

Exploring highly connected networks of qubits is invaluable for implementing various quantum algorithms and simulations as it allows for entangling qubits with reduced circuit depth. Here, we demonstrate a multi-qubit STAR (Sideband Tone Assisted Rabi driven) gate. Our scheme is inspired by the ion qubit Mølmer-Sørensen gate and is mediated by a shared photonic mode and Rabi-driven superconducting qubits, which relaxes restrictions on qubit frequencies during fabrication and supports scalability. We achieve a two-qubit gate with maximum state fidelity of 0.95 in 310 ns, a three-qubit gate with state fidelity 0.905 in 217 ns, and a four-qubit gate with state fidelity 0.66 in 200 ns. Furthermore, we develop a model of the gate that show the four-qubit gate is limited by shared resonator losses and the spread of qubit-resonator couplings, which must be addressed to reach high-fidelity operations.

quant-ph↗

arXiv2022

Local and Nonlocal Transport Spectroscopy in Planar Josephson Junctions

We report simultaneously acquired local and nonlocal transport spectroscopy in a phase-biased planar Josephson junction based on an epitaxial InAs/Al hybrid two-dimensional heterostructure. Quantum point contacts at the junction ends allow measurement of the 2 x 2 matrix of local and nonlocal tunneling conductances as a function of magnetic field along the junction, phase difference across the junction, and carrier density. A closing and reopening of a gap was observed in both the local and nonlocal tunneling spectra as a function of magnetic field. For particular tunings of junction density, gap reopenings were accompanied by zero-bias conductance peaks (ZBCPs) in local conductances. End-to-end correlation of gap reopening was strong, while correlation of local ZBCPs was weak. A simple, disorder-free model of the device shows comparable conductance matrix behavior associated with a topological phase transition. Phase dependence helps distinguish possible origins of the ZBCPs.

cond-mat.mes-hall↗

arXiv2022

Phase coexistence and associated non-equilibrium dynamics under simultaneously applied magnetic field and pressure

A quantitative estimation of the effect of simultaneously applied external pressure (P) and magnetic field (H) on the phase coexistence has been presented for Pr0.5Ca0.5Mn0.975Al0.025O3 and La0.5Ca0.5MnO3, where the ferromagnetic (FM)-metal and antiferromagnetic (AFM)-insulator phases compete in real space. We found that the nonequilibrium dynamics across the FM-AFM transition is primarily dictated by the effect of P and H on the supercooling, superheating temperatures, and the nucleation and growth rate of the equilibrium phase. These effects across the transition is also responsible for the relative volume fraction of the competing phases at low temperature. Importantly in the entire magnetic field-pressure-temperature range of phase coexistence, the interface between the two competing phases having different spin and structural order plays a very important role in controlling the non-equilibrium dynamics.

cond-mat.mtrl-sci↗

arXiv2022

New Horizons: Scalar and Vector Ultralight Dark Matter

The last decade has seen unprecedented effort in dark matter model building at all mass scales coupled with the design of numerous new detection strategies. Transformative advances in quantum technologies have led to a plethora of new high-precision quantum sensors and dark matter detection strategies for ultralight ($<10\,$eV) bosonic dark matter that can be described by an oscillating classical, largely coherent field. This white paper focuses on searches for wavelike scalar and vector dark matter candidates.

hep-ex↗

arXiv2022

Signatures of a topological phase transition in a planar Josephson junction

A growing body of work suggests that planar Josephson junctions fabricated using superconducting hybrid materials provide a highly controllable route toward one-dimensional topological superconductivity. Among the experimental controls are in-plane magnetic field, phase difference across the junction, and carrier density set by electrostatic gate voltages. Here, we investigate planar Josephson junctions with an improved design based on an epitaxial InAs/Al heterostructure, embedded in a superconducting loop, probed with integrated quantum point contacts (QPCs) at both ends of the junction. For particular ranges of in-plane field and gate voltages, a closing and reopening of the superconducting gap is observed, along with a zero-bias conductance peak (ZBCP) that appears upon reopening of the gap. Consistency with a simple theoretical model supports the interpretation of a topological phase transition. While gap closings and reopenings generally occurred together at the two ends of the junction, the height, shape, and even presence of ZBCPs typically differed between the ends, presumably due to disorder and variation of couplings to local probes.

cond-mat.mes-hall↗

arXiv2021

Three-dimensional ferrimagnetic ground state of triangular-lattice system Ca3Co2O6

High temperature one-dimensional (1D) ferromagnetic (FM) chains in Ca3Co2O6 spin system are subjected to a magnetic field and temperature induced first order phase transition (FOPT) to 3D ferrimagnetic (FIM) ground state with decrease in temperature (T). Weak-FM interaction of third nearest-neighbor(nn) interchain removes the frustration effect arising from antiferromagnetic (AFM) interactions of first-nn and second-nn interchains in the underlying triangular-lattice resulting a 3D FIM ordering of 1D FM chains at low T. However, hindered kinetics of FOPT partially masks this tranformation giving rise to coexistence of non-interacting 1D FM chains with 3D-FIM state at low-T. The existence of all these couplings is further confirmed here by random substitution of S = 5/2 magnetic-impurity into the spin chain of original system. It reveals weakening of FM interactions of both intrachain and third-nn surrounding chains respectively without significant modulation in the AFM coupling of first-nn and second-nn interchains. Thus, influence of AFM interactions is enhanced as compared to effective FM coupling with increase of S = 5/2 impurity content resulting instability of 3D long-range FIM state at low-T.

cond-mat.str-el↗

arXiv2021

Search for oscillations of fundamental constants using molecular spectroscopy

A possible implication of an ultralight dark matter (UDM) field interacting wibeginth the Standard Model (SM) degrees of freedom is oscillations of fundamental constants. Here, we establish direct experimental bounds on the coupling of an oscillating UDM field to the up, down, and strange quarks and to the gluons, for oscillation frequencies between 10 Hz and 10^8 Hz. We employ spectroscopic experiments that take advantage of the dependence of molecular transition frequencies on the nuclear masses. Our results apply to previously unexplored frequency bands, and improve on existing bounds at frequencies > 5 MHz. We identify a sector of UDM - SM coupling space where the bounds from Equivalence Principle tests may be challenged by next-generation experiments of the present kind.

hep-ph↗

arXiv2021

Role of electronic excitation on the anomalous magnetism of elemental Copper

Magnetic susceptibility of elemental copper (Cu) shows an anomalous rise at low temperatures superimposed on the expected atypical diamagnetic response. Such temperature dependent susceptibility, which is also known as the Curie tail, can not be explained on the basis of Larmor diamagnetic and Pauli paramagnetic contributions expected in Cu. Using valence band resonant photoemission spectroscopy results and density functional theory calculations, we show the magnetic anomaly appears due to presence of holes in Cu 3d band, which originates from thermally excited electronic configuration. Our study therefore highlights that the Curie tail, which is generally overlooked presuming it either due to paramagnetic impurities or defects, can in fact be intrinsic to a material, and even simple systems like elemental Cu is susceptible to electronic excitations giving rise to anomalous magnetic state.

cond-mat.mtrl-sci↗