Sourabh Barua
@bitmesra.ac.in
BIT Mesra Ranchi
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Rathindranath Biswas, Saptarshi Ghosh Dastider, Imtiaz Ahmed, Sourabh Barua, Krishnakanta Mondal, and Krishna Kanta Haldar
American Chemical Society (ACS)
Unraveling the origins of the electrocatalytic activity of composite nanomaterials is crucial but inherently challenging. Here, we present a comprehensive investigation of the influence of different orbitals' interaction in the AuAgCu nanobowl model electrocatalyst during the hydrogen evolution reaction (HER). According to our theoretical study, AgAuCu exhibits a lower energy barrier than AgAu and AgCu bimetallic systems for the HER, suggesting that the trimetallic AgAuCu system interacts optimally with H*, resulting in the most efficient HER catalyst. As we delve deeper into the HER activity of AgAuCu, it was observed that the presence of Cu allows Au to adsorb the H* intermediate through the hybridization of s orbitals of hydrogen and s, dx2-y2, and dz2 orbitals of Au. Such orbital interaction was not present in the cases of AgAu and AgCu bimetallic systems, and as a result, these bimetallic systems exhibit lower HER activities.
Jonas A. Krieger, Daniel Tay, Igor P. Rusinov, Sourabh Barua, Pabitra K. Biswas, Lukas Korosec, Thomas Prokscha, Thorsten Schmitt, Niels B. M. Schröter, Tian Shang,et al.
American Physical Society (APS)
Layered transition-metal dichalcogenides are proposed as building blocks for van der Waals (vdW) heterostructures due to their graphene-like two dimensional structure. For this purpose, a magnetic semiconductor could represent an invaluable component for various spintronics and topotronics devices. Here, we combine different local magnetic probe spectroscopies with angle-resolved photoemission and density-functional theory calculations to show that 2H-MoTe2 is on the verge of becoming magnetic. Our results present clear evidence that the magnetism can be"switched on"by a hydrogen-like impurity. We also show that this magnetic state survives up to the free surface region, demonstrating the material's potential applicability as a magnetic component for thin-film heterostructures.
Swarnava Mitra, Aditya Mishra, and Sourabh Barua
IOP Publishing
Abstract This experiment is developed with the aim of designing a temperature-controlled sample holder by using a commonly available power transistor as the heating element. Most temperature-controlled sample holders use commonplace heaters, which are made of high resistance materials like nichrome 80/20 (80% nickel, 20% chromium) wire and similar materials. The fabrication of this temperature-controlled sample holder also leads to the usage of high power electronic components, like power transistors and power resistors which are, otherwise, neglected in most laboratory experiments. Moreover, to develop this system, Arduino Uno Rev3 and resistance temperature detector (RTD) were used for the purposes of data acquisition and temperature measurement, respectively. Arduino is a single board micro-controller and RTD functions as a temperature sensor. This experiment serves as a good example of application and unification of basic concepts of electronics, heat and thermodynamics and offers an insight into data acquisition. The experiment is non-proprietary, and the apparatus is entirely made from off-the-shelf items. Thus, reconstruction and use will be simple and inexpensive. The power transistor, along with the power resistors, generates enough heat to raise the temperature of the sample holder by about 100 K. Also, to exhibit the working of the sample-holder, the energy band gap of the material of a p–n junction diode (silicon) has been determined experimentally using the setup.
G. Vinai, C. Bigi, A. Rajan, M. D. Watson, T.-L. Lee, F. Mazzola, S. Modesti, S. Barua, M. Ciomaga Hatnean, G. Balakrishnan,et al.
American Physical Society (APS)
Among transition-metal dichalcogenides, mono and few-layers thick ${\\mathrm{VSe}}_{2}$ has gained much recent attention following claims of intrinsic room-temperature ferromagnetism in this system, which have nonetheless proved controversial. Here, we address the magnetic and chemical properties of $\\mathrm{Fe}/{\\mathrm{VSe}}_{2}$ heterostructure by combining element sensitive x-ray absorption spectroscopy and photoemission spectroscopy. Our x-ray magnetic circular dichroism results confirm recent findings that both native mono/few-layer and bulk ${\\mathrm{VSe}}_{2}$ do not show intrinsic ferromagnetic ordering. Nonetheless, we find that ferromagnetism can be induced, even at room temperature, after coupling with a Fe thin film layer, with antiparallel alignment of the moment on the V with respect to Fe. We further consider the chemical reactivity at the $\\mathrm{Fe}/{\\mathrm{VSe}}_{2}$ interface and its relation with interfacial magnetic coupling.
Laxmi Narayan Tripathi and Sourabh Barua
Elsevier BV
Abstract This review article covers the growth and characterization of two-dimensional (2D) crystals of transition metal chalcogenides, h-BN, graphene, etc. The chemical vapor transport method for bulk single crystal growth is discussed in detail. Top-down methods like mechanical and liquid exfoliation and bottom-up methods like chemical vapor deposition and molecular beam epitaxy for mono/few-layer growth are described. The optimal characterization techniques such as optical, atomic force, scanning electron, and Raman spectroscopy for identification of mono/few-layer(s) of the 2D crystals are discussed. In addition, a survey was done for the application of 2D crystals for both creation and deterministic transfer of single-photon sources and photovoltaic systems. Finally, the application of plasmonic nanoantenna was proposed for enhanced solar-to-electrical energy conversion and faster/brighter quantum communication devices.
Jiagui Feng, Deepnarayan Biswas, Akhil Rajan, Matthew D. Watson, Federico Mazzola, Oliver J. Clark, Kaycee Underwood, Igor Marković, Martin McLaren, Andrew Hunter,et al.
American Chemical Society (ACS)
How the interacting electronic states and phases of layered transition-metal dichalcogenides evolve when thinned to the single-layer limit is a key open question in the study of two-dimensional materials. Here, we use angle-resolved photoemission to investigate the electronic structure of monolayer VSe2 grown on bilayer graphene/SiC. While the global electronic structure is similar to that of bulk VSe2, we show that, for the monolayer, pronounced energy gaps develop over the entire Fermi surface with decreasing temperature below Tc = 140 ± 5 K, concomitant with the emergence of charge-order superstructures evident in low-energy electron diffraction. These observations point to a charge-density wave instability in the monolayer that is strongly enhanced over that of the bulk. Moreover, our measurements of both the electronic structure and of X-ray magnetic circular dichroism reveal no signatures of a ferromagnetic ordering, in contrast to the results of a recent experimental study as well as expectations from density functional theory. Our study thus points to a delicate balance that can be realized between competing interacting states and phases in monolayer transition-metal dichalcogenides.
Sourabh Barua, M. Ciomaga Hatnean, M. R. Lees, and G. Balakrishnan
Springer Science and Business Media LLC
VSe2 is a transition metal dichaclogenide which has a charge- density wave transition that has been well studied. We report on a low-temperature upturn in the resistivity and, at temperatures below this resistivity minimum, an unusual magnetoresistance which is negative at low fields and positive at higher fields, in single crystals of VSe2. The negative magnetoresistance has a parabolic dependence on the magnetic field and shows little angular dependence. The magnetoresistance at temperatures above the resistivity minimum is always positive. We interpret these results as signatures of the Kondo effect in VSe2. An upturn in the susceptibility indicates the presence of interlayer V ions which can provide the localized magnetic moments required for scattering the conduction electrons in the Kondo effect. The low-temperature behaviour of the heat capacity, including a high value of γ, along with a deviation from a Curie-Weiss law observed in the low-temperature magnetic susceptibility, are consistent with the presence of magnetic interactions between the paramagnetic interlayer V ions and a Kondo screening of these V moments.
Sourabh Barua and K.P. Rajeev
Elsevier BV
Abstract We performed angle dependent magnetoresistance study of a metallic single crystal sample of Bi2Te3. We find that the magnetoresistance is highly asymmetric in positive and negative magnetic fields for small angles between the magnetic field and the direction perpendicular to the plane of the sample. The magnetoresistance becomes symmetric as the angle approaches 90°. The quantum Shubnikov de-Haas oscillations are symmetric and show signatures of topological surface states with Dirac dispersion in the form of non-zero Berry phase. However, the angular dependence of these oscillations suggests a complex three dimensional Fermi surface as the source of these oscillations, which does not exactly conform with the six ellipsoidal model of the Fermi surface of Bi2Te3. We attribute the asymmetry in the magnetoresistance to a mixing of the Hall voltage in the longitudinal resistance due to the comparable magnitude of the Hall and longitudinal resistance in our samples. This provides a clue to understanding the asymmetric magnetoresistance often seen in this and similar materials. Moreover, the asymmetric nature evolves with exposure to atmosphere and thermal cycling, which we believe is either due to exposure to atmosphere or thermal cycling, or both affecting the carrier concentration and hence the Hall signal in these samples. However, the quantum oscillations seem to be robust against these factors which suggests that the two have different origins.
Sourabh Barua, K P Rajeev, and Anjan K Gupta
IOP Publishing
Bi2Te3 is a member of a new class of materials known as topological insulators which are supposed to be insulating in the interior and conducting on the surface. However, experimental verification of the conductive qualities of the surface states has been hindered by parallel bulk conductions. We report low temperature magnetotransport measurements on single crystal samples of Bi2Te3. We observe metallic character in our samples and large and linear magnetoresistance from 1.5 K to 290 K with prominent Shubnikov-de Haas (SdH) oscillations whose traces persist up to 20 K. Even though our samples are metallic, we are able to obtain a Berry phase close to the value of π, which is expected for Dirac fermions of the topological surface states. This indicates that we have obtained evidence for the topological surface states in metallic single crystals of Bi2Te3. Other physical measurements obtained from the analysis of the SdH oscillations are also in close agreement with those reported for the topological surface states. The linear magnetoresistance observed in our sample, which is considered as a signature of the Dirac fermions of the surface states, lends further credence to the existence of topological surface states.
Sourabh Barua and K. P. Rajeev
AIP Publishing LLC
Topological insulators have a conducting surface and an insulating bulk. Resistivity, as defined for a three dimensional conductor, should increase linearly with thickness in case of topological insulators. This is because resistivity is proportional to both resistance and thickness, and the surface conductance of a topological insulator should be independent of the thickness of the topological insulator. Thus, operationally, thickness dependence of resistivity could be one of the important tests in determining whether any material is a topological insulator or not. In this work, we have done a meta-analysis of the electrical transport data reported in the literature on topological insulators. However, many of the data do not follow any linear trend with thickness as is expected in the case of topological insulators. Thus we arrive at the conclusion from the existing data in the literature, that all of these materials cannot be considered as true topological insulators.
Sourabh Barua and K. P. Rajeev
AIP Publishing
In this report, we scrutinize the thickness dependent resistivity data from the recent literature on electrical transport measurements in topological insulators. A linear increase in resistivity with increase in thickness is expected in the case of these materials since they have an insulating bulk and a conducting surface. However, such a trend is not seen in the resistivity versus thickness data for all the cases examined, except for some samples, where it holds for a narrow range of thickness. PACS numbers: 73.25.+i, 73.20.-r, 03.65.Vf
Sourabh Barua, Rohan Poojary, and K. P. Rajeev
AIP
We report coulomb blockade and coulomb staircase at liquid nitrogen temperatures in the current/voltage characteristics of a lateral metal nanostructure made with the help of a focussed ion beam.