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Co doped Bi2Se3 topological insulator: a combined theoretical and experimental study

Materials Science in Semiconductor Processing 2025年 195卷

作者： Kumar, Ravi Sisodiya, D.S. Vijay, Kritika Banik, Soma Sen, Shashwati Babu, P.D. Bhattacharyya, Dibyendu Atomic and Molecular Physics Division Bhabha Atomic Research Centre Mumbai400085 India Homi Bhabha National Institute Anushaktinagar Mumbai400094 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Technical Physics Division Bhabha Atomic Research Centre Mumbai400085 India UGC-DAE Consortium for Scientific Research Mumbai Centre Mumbai400085 India

Research on magnetic ion doping in topological insulators like Bi2Se3 is gaining prominence rapidly since it has prospective technological implications and also has significant importance in experimental verification of exotic fundamental physical concepts. In this study, we present a comprehensive investigation of Co-doped Bi2Se3 by integrating advanced ab initio density functional theory (DFT) calculations with an array of experimental techniques including X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS) and angle-resolved photoemission spectroscopy (ARPES) using synchrotron radiation. This detailed approach goes beyond previous research by not only confirming the long-range crystalline order but also providing a detailed insight into the local atomic environment and electronic structure around Co dopants. Our combined theoretical and experimental investigations undoubtedly reveal that Co atoms preferentially occupy interstitial sites within the van der Waals gap, a result which has provided conclusive clarity regarding the preferred sites for Co doping in Bi2Se3. Apart from the above, our theoretical study corroborated by experimental results also explains how Co doping affects magnetic properties of Bi2Se3. This enhanced understanding of the interplay between dopant site preference, oxidation state, and resultant magnetic behavior is pivotal for designing next generation topological insulator-based devices with optimized performance. © 2025 Elsevier Ltd

关键词： Photoelectron spectroscopy

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Metal-insulator transition in FeSex originating in an anomalous lattice effect

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Physical Review B 2025年第8期111卷 085123-085123页

作者： Shubham Purwar Shinjini Paul Kritika Vijay R. Venkatesh Soma Banik P. Mahadevan S. Thirupathaiah Department of Condensed Matter and Materials Physics S. N. Bose National Centre for Basic Sciences Kolkata West Bengal 700106 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore 452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai 400094 India UGC-DAE Consortium for Scientific Research DAVV Campus Indore 452001 Madhya Pradesh India

We present a comprehensive investigation of the structural, electrical transport, and magnetic properties of FeSex (x = 1.14, 1.18, 1.23, 1.28, and 1.32) to unravel the mechanism of the metal-insulator transition observed in these systems. For this, we systematically evaluated the structural parameters of FeSex as a function of Se concentration and temperature. We observe increased lattice constants and cell volume with increased Se concentration. On the other hand, the temperature-dependent x-ray diffraction studies suggest unusual lattice change around the metal-insulator (MI) transition temperature of the respective compositions. This remarkable observation suggests that the MI transition originates in the anomalous lattice effect in these systems. Additionally, our density of states (DOS) calculations on FeSe1.14 qualitatively explain the MI transition, as the low-temperature (50 K) structure DOS suggests a metallic nature and the high-temperature (300 K) structure DOS shows a gap near the Fermi level.

关键词： Metal insulator transition

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Localized Radiofrequency Heating for Enhanced Thermoelectric Energy Generation Using Natural Galena Ore

arXiv

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arXiv 2025年

作者： Karthik, R. Zheng, Yiwen Sahu, Rajesh Kumar Sreeram, Punathil Raman Banik, Soma Vashisth, Aniruddh Tiwary, Chandra Sekhar Department of Metallurgical and Materials Engineering Indian Institute of Technology West Bengal Kharagpur India Department of Mechanical Engineering University of Washington SeattleWA United States Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai400094 India

The efficiency of thermoelectric devices can be significantly enhanced by maintaining a stable temperature gradient, which can be achieved through localized heating. Radio waves serve as an ideal heat source for this purpose. In this study, we demonstrate the enhancement of thermoelectric performance in earth-abundant natural ore Galena (PbS) through localized radio frequency (RF) heating. RF heating experiments conducted at frequencies between 35 and 45 MHz induced substantial localized heating in PbS, generating a temperature gradient of 32 K. This resulted in a Seebeck voltage of -5.8 mV/K, approximately 13 times greater than the conventional Seebeck coefficient of PbS (440 μV/K). Additionally, a power factor of 151 mWm-1K-2 and an overall RF to thermoelectric conversion efficiency of 15% were achieved. Molecular dynamics simulations corroborate the experimental findings, providing insights into the mechanism of thermal transport and RF induced heating in PbS. These results highlight the potential of localized RF heating as an effective strategy for enhancing thermoelectric performance, with promising implications for ambient thermoelectric energy harvesting applications. Copyright © 2025, The Authors. All rights reserved.

关键词： Energy harvesting

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Electronic, magnetic and thermal behavior near the Invar compositions of Fe-Ni alloys

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Journal of Electron Spectroscopy and Related Phenomena 2025年 280卷

作者： Sahoo, Ananya Biswal, Ayusa Aparupa Parida, S.K. Medicherla, V.R.R. Behera, Soumya Shephalika Singh, M.N. Sagdeo, A. Datta, Sawani Singh, Abhishek Maiti, Kalobaran Department of Physics ITER Siksha ‘O’ Anusandhan Deemed to be University Bhubaneswar751030 India UGC-DAE Consortium for Scientific Research University Campus Khandwa Road Indore452001 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai400094 India Department of Condensed Matter Physics and Materials Science Tata Institute of Fundamental Research Homi Bhabha Road Colaba Mumbai400005 India

The structural, magnetic and electronic properties of Fe1−xNix (x = 0.32, 0.36, 0.40, 0.50) alloys have been investigated using synchrotron based x-ray diffraction (XRD), superconducting quantum interference device (SQUID) magnetometer and the high resolution x-ray photoelectron spectroscopy (XPS) measurements. The XRD measurement was done down to 50 K temperature. The XRD studies suggest a single phase with fcc structure for x = 0.36, 0.40, and 0.50 alloys and a mixed phase for x = 0.32 alloy containing both bcc and fcc structures. The lattice parameter of the alloys exhibits a linear dependence on temperature giving rise to a temperature independent coefficient of thermal expansion (CTE). The lowest CTE is observed for x = 0.36 Invar alloy as expected while x = 0.50 alloy exhibits the highest CTE among the alloys studied. The CTE of the fcc component of mixed phase alloy is close to that of Invar alloy. The temperature dependence of magnetization of the alloys down to 2 K reveals an overall antiferromagnetic interactions within the ferromagnetic phase causing the magnetization decreasing with lowering temperature. The field cooled and zero field cooled data show larger differences for the Invar compositions;this is also manifested in the magnetic hysteresis data at 2 K and 300 K. The Fe 2p and Ni 2p core level spectra exhibit spin–orbit split features along with a satellite feature in the Ni 2p spectra. The spectral line shapes are almost similar for all the compositions studied. Interestingly, the spin–orbit splitting for Fe 3p spectra is larger than that observed for Ni 3p suggesting additional contributions due to the exchange interaction between the Fe 3p core hole with the Fe 3d moment. This suggests large magnetic moment contribution from Fe as expected. The core level and valence band spectra, and the magnetization data suggest significant role of disorder for the Invar compositions. © 2025

关键词： SQUIDs

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Anomalous Lattice Effect Originated Metal-Insulator Transition in FeSex

arXiv

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arXiv 2025年

作者： Purwar, Shubham Paul, Shinjini Vijay, Kritika Venkatesh, R. Banik, Soma Mahadevan, P. Thirupathaiah, S. Department of Condensed Matter and Materials Physics S. N. Bose National Centre for Basic Sciences West Bengal Kolkata700106 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai400094 India UGC-DAE Consortium for Scientific Research DAVV Campus MP Indore452001 India

We present a comprehensive investigation of the structural, electrical transport, and magnetic properties of FeSex (x = 1.14, 1.18, 1.23, 1.28, and 1.32) to unravel the mechanism of the metal-insulator transition observed in these systems. For this, we systematically evaluated the structural parameters of FeSex as a function of Se concentration and temperature. We observe increased lattice constants and cell volume with increased Se concentration. On the other hand, the temperature-dependent XRD studies suggest unusual lattice change around the metal-insulator (MI) transition temperature of the respective compositions. This remarkable observation suggests that the anomalous lattice effect originates the MI transition in these systems. Additionally, our density of states (DOS) calculations on FeSe1.14 qualitatively explain the MI transition, as the low-temperature (50 K) structure DOS suggests a metallic nature and the high-temperature (300 K) structure DOS shows a gap near the Fermi level. © 2025, CC BY.

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Anomalies in the electronic, magnetic and thermal behavior near the Invar compositions of Fe-Ni alloys

arXiv

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arXiv 2025年

作者： Sahoo, Ananya Biswal, Ayusa Aparupa Parida, S.K. Medicherla, V.R.R. Behera, Soumya Shephalika Singh, M.N. Sagdeo, A. Datta, Sawani Singh, Abhishek Maiti, Kalobaran Department of Physics ITER Siksha’O’ Anusandhan Deemed to be University Bhubaneswar751030 India UGC-DAE Consortium for Scientific Research University Campus Khandwa Road Indore452001 India Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai400094 India Department of Condensed Matter Physics and Materials Science Tata Institute of Fundamental Research Homi Bhabha Road Colaba Mumbai400005 India

The structural and magnetic properties of Fe1−xNix (x = 0.32, 0.36, 0.40, 0.50) alloys have been investigated using synchrotron based x-ray diffraction (XRD) technique with x-rays of wavelength 0.63658 Å down to 50 K temperature, magnetic measurement using superconducting quantum interference device (SQUID) magnetometer and high resolution x-ray photoelectron spectroscopy (XPS) with monochromatic AlKα radiation. The XRD studies suggest a single phase with fcc structure for x = 0.36, 0.40, and 0.50 alloys and a mixed phase for x = 0.32 alloy containing both bcc and fcc structures. The lattice parameter of the alloys exhibits a linear dependence on temperature giving rise to a temperature independent coefficient of thermal expansion (CTE). The lowest CTE is observed for x = 0.36 Invar alloy as expected while x = 0.50 alloy exhibits the highest CTE among the alloys studied. The CTE of the fcc component of mixed phase alloy is close to that of Invar alloy. The temperature dependence of magnetization of the alloys down to 2 K reveals an overall antiferromagnetic interactions within the ferromagnetic phase causing the magnetization decreasing with cooling. The field cooled and zero field cooled data show larger differences for the Invar compositions;this is also manifested in the magnetic hysteresis data at 2 K and 300 K. The Fe 2p and Ni 2p core level spectra exhibit spin-orbit split features along with a satellite feature in the Ni 2p spectra. The spectral lineshape are almost similar for all the compositions studied. Interestingly, the spin-orbit splitting for Fe 3p spectra is larger than that observed for Ni 3p suggesting additional contributions due to the exchange interaction between the Fe 3p core hole with the Fe 3d moment. This suggests large magnetic moment contribution from Fe as expected. The core level and valence band spectra, and the magnetization data suggest significant role of disorder for the Invar compositions. © 2025, CC BY.

关键词： SQUIDs

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Strain induced stabilization of high symmetry phase in MAPbBr3 perovskite

arXiv

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arXiv 2025年

作者： Dutt, Shankar Bhattacharya, Joydipto Kumar, Kailash Urkude, Rajashri Sagdeo, Pankaj R. Sagdeo, Archna Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore452013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai400094 India Tyndall National Institute University College Cork CorkT12R5CP Ireland Materials Research Laboratory Department of Physics Indian Institute of Technology Indore453552 India Beamline Development and Application Section Bhabha Atomic Research Center Trombay Mumbai400085 India

Structural phase transitions in the organic inorganic metal halide perovskites are driven via rearrangement of methylammonium cation and distortion in the PbX6 octahedra. Compositional tuning is usually incorporated for suppression of the structural phase transition in these systems with cation or anion tuning. Along with the compositional tuning, behaviour of strain present in the system can also lead to stabilization of single phase in these systems. In the present investigation, two different samples of CH3NH3PbBr3 perovskite were studied and it is observed that structural phase transition is absent for one of the sample while it is present in the other sample. The non-observance of structural phase transition and stabilization of single phase has been attributed to the perceived tensile strain in the system contrary to the compressive strain observed in the system showing structural phase transitions. This observation is further supported by theoretical calculations. Extended X-ray absorption fine structure measurements revealed distorted octahedra with varying bond lengths along planar and axial directions in both samples, along with observed increase in bond lengths in one of the sample. This stabilization of the cubic phase can enhance device performance and increase overall environmental stability, making these systems more effective for practical applications. © 2025, CC BY.

关键词： Perovskite

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Finite Element Analysis of Squeezed Film Damping on Trapezoidal Microcantilever Resonators at Different Pressure Levels 6th

Finite Element Analysis of Squeezed Film Damping on Trapezoi...

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6th Conference on Microactuators, Microsensors and Micromechanisms, MAMM 2022

作者： Sharma, Varun P. Shukla, Rahul Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Madhya Pradesh Indore India Homi Bhabha National Institute Maharashtra Anushaktinagar Mumbai India

ISBN: (纸本)9783031203527

Squeezed film damping (SFD) becomes a dominant damping mechanism in micro-electro-mechanical system (MEMS). Depending on the pressure variation in MEMS, SFD governs the dynamic parameters like quality factors (Q factors) and damping ratio. In the present paper, we calculate the Q factor and damping ratio of the trapezoidal shaped microcantilever beam by eigenfrequency analysis using finite element method (FEM) in COMSOL Multiphysics. The effective viscosity method is used to calculate the SFD in FEM for the continuum, slip, transition and molecular flow regimes as described by the Knudsen no. (Kn). Kn is varied by altering the operating pressure, keeping the thickness of air gap constant. It is observed that the Q factor and damping ratio of trapezoidal microcantilever beam varies by an order of million for different flow regimes with the change of operating pressure from atmospheric to 0.1 Pa. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Multiphysics

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Zero-Valent Copper Catalysis Enables Regio- and Stereoselective Difunctionalization of Alkynes

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Angewandte Chemie 2025年第8期137卷

作者： Aishwarya Prakash Suma Basappa Rajashri R. Urkude Ravindra Jangir Rajendra S. Dhayal Shubhankar Kumar Bose Centre for Nano and Material Sciences (CNMS) Jain University Jain Global Campus Bangalore 562112 India Beamline Development & Application Section Bhabha Atomic Research Centre Trombay Mumbai 400085 India Accelerator Physics and Synchrotrons Utilization Division RRCAT Indore 452013 India Department of Chemistry School of Basic and Applied Sciences Central University of Punjab Bathinda 151401 India

The development of a metallic copper-based catalyst system remains a significant challenge. Herein, we report the synthesis of highly stable, active, and reusable Cu 0 catalyst for the carboboration of alkynes using carbon electrophiles and bis (pinacolato)diboron (B 2 pin 2 ) as chemical feedstocks to afford di- and trisubstituted vinylboronate esters in a regio- and stereoselective manner with appreciable turnover number (TON) of up to 2535 under mild reaction conditions. This three-component coupling reaction works well with a variety of substituted electrophiles and alkynes with broad functional group tolerance. In addition, a wide range of terminal and challenging internal alkynes were efficiently converted into hydroborated products in up to >99 % yield with excellent regioselectivity in the absence of carbon electrophiles. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) analysis confirm that the oxidation state of the copper in the catalyst is zero. The broad range of organic transformations, effectiveness, and recyclability of this Cu 0 catalyst are the major achievements that provide an environmentally friendly route for the efficient production of tri- and tetrasubstituted olefins, key intermediates in organic synthesis. The gram-scale reaction and synthetic transformations further highlights the usefulness of these methods.

关键词： Alkenylboronate esters Alkynes Carboboration Metallic copper catalysis Regioselectivity

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Structural and magnetic properties of V-Ti-Si alloy superconductors

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AIP Conference Proceedings 2025年第1期3198卷

作者： Asi Khandelwal L. S. Sharath Chandra Archna Sagdeo Rashmi Singh M. K. Chattopadhyay Free Electron Laser Utilization Laboratory Raja Ramanna Centre for Advanced Technology Indore Madhya Pradesh - 452 013 India Homi Bhabha National Institute Training School Complex Anushakti Nagar Mumbai 400 094 India Hard X-ray Applications Laboratory Accelerator Physics and Synchrotrons Utilization Division Raja Ramanna Centre for Advanced Technology Indore Madhya Pradesh - 452 013 India Nano-Functional Materials Laboratory Laser and Functional Materials Division Raja Ramanna Centre for Advanced Technology Indore Madhya Pradesh - 452 013 India

The structural and magnetic properties of the as-cast and annealed V0.6-xSixTi0.4 (x = 0, 0.05, 0.10, 0.15) alloy superconductors are reported here. It is found that addition of silicon to the V-Ti alloys results in eutectic precipitation of Ti5Si3-phase in the body centered cubic (bcc) β-V-Ti matrix. In the as-cast V0.6-xSixTi0.4 alloys, the superconducting transition temperature (TC) changes non-monotonically with increasing silicon content whereas after annealing, it is about 7.7 K for all the alloys. On the other hand, the upper critical field decreases and the coherence length increases after annealing in the x = 0.10 alloy. The variations in the superconducting properties in the alloys are related to the solubility of 4-6 at.% Si in the V0.60Ti0.40 alloy and the lattice contraction in the β phase due to the precipitation of Ti5Si3 phase.

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