Area-driven bosonic superconductor–insulator transition in disordered indium oxide strips Girish C Tewari, Sreemanta Mitra, Dan Shahar Superconductor Science and Technology, 2026 In disordered electronic systems, the zero-temperature ( T ) conductance was proposed to scale with the system’s effective length. Many efforts have been made to establish this for the superconductor-to-insulator transition (SIT) observed in disordered superconductors. While several external parameters have been shown to scale the T = 0 conductance, scaling with the physical sample size has never been observed. Here, we systematically study the low-temperature electrical transport behavior of co-fabricated amorphous indium oxide (a:InO) strips of varying areas at zero magnetic field. Larger area devices exhibited a superconducting ground state, while devices with reduced area showed an insulating ground state, indicating a SIT. Crucially, we scaled the SIT in a:InO strips with the sample’s area ( L 2 ), providing the first direct evidence that the transition can be driven by area alone, independent of width, length, or any other external parameter. Additionally, at the transition point, the resistance per square ( R ◻ ) was found to be close to the quantum resistance of Cooper pairs ( R Q = h / ( 2 e ) 2 ≈ 6.45 kΩ), consistent with a quantum phase transition governed primarily by phase fluctuations rather than amplitude suppression, further indicating that Cooper pairs remain intact across the transition. This finding contributes to the long-debated nature of SIT, supporting the prevalence of bosonic behavior.
Correlating Carrier Localization to Optoelectronic Behavior of Monolayer MoS2 Arup Singha, Aparna P, Agniva Paul, Sanjitha K. Shetty, Kenji Watanabe, Takashi Taniguchi, Arindam Ghosh, Sreemanta Mitra ACS Applied Materials and Interfaces, 2025 In nanoscale semiconductor devices, electrical conductivity is significantly influenced by inherent disorder. This study examines the electrical transport properties of a single-layer MoS 2 field-effect transistor on a few-layered hBN substrate. Temperature-dependent transport measurements reveal that electrical conductivity is predominantly governed by a combination of simple activated and variable-range hopping mechanisms. The calculations on the experimental data yield a localization length around 5 nm for a typical defect density near the Fermi energy as 10 14 eVcm –2 . Additionally, optoelectronic transport measurements exhibit temperature-dependent persistent photoconductivity, attributed to electron localization within defect states. Calculations based on the temperature-dependent photoconductivity relaxation indicate a localization length of 7 nm, suggesting a direct correlation between the two phenomena.
Optical intensity driven mid-gap transitions in few-layer MoS2 Tara Shankar Bhattacharya, Sumanti Patra, Shib Shankar Singha, Sreemanta Mitra, Priya Mahadevan, Achintya Singha Physical Review B, 2025 The utilization of semiconducting two-dimensional (2D) materials in photonics or optoelectronics depends on having a tunable optical band gap, typically influenced by the material's layer count and modified interlayer interactions. Extensive research has been conducted on semiconducting transition metal dichalcogenides to explore their potential in light-matter applications through the manipulation of electronic states' interactions. Notably, intrinsic defects in these 2D materials generate electronic states within the mid-gap regions, enhancing their versatility as promising candidates for potential optoelectronic applications. In this study, we realized the optical transitions from the mid-gap states in liquid-phase exfoliated ${\mathrm{MoS}}_{2}$ through varying light intensity. We note the emergence and reversible evolution of two additional photoluminescence emissions at lower energy, complementing the standard photoluminescence spectra of ${\mathrm{MoS}}_{2}$ at room temperature. Our density functional theory simulations indicate that these novel optical pathways stem from sulfur vacancy defect states in the mid-gap regions and the intensity of the optical excitation can be used to tune the transitions. This finding presents an exciting opportunity for further investigation and control of mid-gap states, which could have potential applications in optical communication.
Interlayer Charge Transfer and Photodetection Efficiency of Graphene-Transition-Metal-Dichalcogenide Heterostructures Aparna Parappurath, Sreemanta Mitra, Gagandeep Singh, Navkiranjot Kaur Gill, Tanweer Ahmed, T. Phanindra Sai, Kenji Watanabe, Takashi Taniguchi, Arindam Ghosh Physical Review Applied, 2022 Graphene and transition-metal-dichalcogenide- (TMD) based van der Waals heterostructures in field-effect-transistor (FET) architecture exhibits extremely high sensitivity to optical radiation due to transit and physical separation of the photogenerated carriers across the heterointerface. Both the sensitivity and speed of these detectors depend on the kinetics of charge transfer, but their interdependency at room temperature (T), where these detectors would be most useful, remains largely unexplored. Here we systematically measure the T dependence of the magnitude (gain) and timescale (bandwidth) of photoresponse in graphene-TMD heterostructures well up to the room T. The gain-bandwidth product is found to be strongly dependent on the power of optical illumination and increases with decreasing power (P), becoming as large as $1\phantom{\rule{0.2em}{0ex}}\mathrm{M}\mathrm{Hz}$ in the low-P limit. We find that thermally activated back transfer of charge from graphene to the TMD determines the response time of the detector at higher temperatures under continuous illumination. Our experiment reveals the impact of charge-transfer pathways on the performance in a broad class of graphene-TMD detectors.
Graphene- WS2 van der Waals Hybrid Heterostructure for Photodetector and Memory Device Applications Sreemanta Mitra, Saloni Kakkar, Tanweer Ahmed, Arindam Ghosh Physical Review Applied, 2020 The intriguing electronic properties of graphene and the strong light-matter interaction in layered transition-metal dichalcogenide (TMDC) make them a natural partner for hybrid devices, not only for optoelectronic device applications, but also to understand the conversion of light to electricity in this atomic scale prototype of a donor-acceptor complex. Here, we describe graphene-on-${\mathrm{WS}}_{2}$ binary heterostructure FET device, displaying gate-tunable persistent photoconductivity. Our time-dependent photovoltage relaxation experiments suggest that the charge-transfer time scale in this heterostructure is dependent on the input optical power, contrary to what is observed for the bare TMDC and is orders of magnitude slower than that observed for various other vdW hybrids. The optoelectronic responsivity of this device at low optical power is found to be as high as ${10}^{10}\phantom{\rule{0.1em}{0ex}}\mathrm{V/W}$, and thus shows the potential to be one of the most sensitive visible range photodetectors, while the gate tunability of the persistent photoconductivity can be utilized in the memory device applications. We identify that the photoresponse is the outcome of a photogating mechanism, due to the exciton dissociation under optical excitation, followed by the trapping of holes in ${\mathrm{WS}}_{2}$ and subsequent electron transfer to graphene.
Tailoring phonon modes of few-layered MoS2 by in-plane electric field Sreemanta Mitra, Divya Srivastava, Shib Shankar Singha, Saurav Dutta, Biswarup Satpati, Maarit Karppinen, Arindam Ghosh, Achintya Singha Npj 2d Materials and Applications, 2020 We discuss the effect of the in-plane electric field on the Raman spectroscopy for few-layered MoS2. The characteristic Raman modes of MoS2 show gradual red shift, while the intensity increases by 45–50% as the electric field is increased, showing a large electro-optical effect. Structural analysis suggests that our few-layered MoS2 belongs to P6/m2 space group with broken inversion symmetry. We attribute this gradual red shift to this broken symmetry-driven piezoelectricity in MoS2, which generates tensile strain along the perpendicular direction when the electric field is applied. The enhancement of the effect upon reversing the electric field direction adds credence to our interpretation. Our first principal density-functional theory calculation further substantiates the claim. This optical probing of the electromechanical coupling may lead to applications as a nonextensive technique for electric field/strain sensors in the nanoelectronics devices.
Probing dipole and quadrupole resonance mode in non-plasmonic nanowire using Raman spectroscopy Sreyan Raha, Sreemanta Mitra, Prasanna Kumar Mondal, Subhajit Biswas, Justin D Holmes, Achintya Singha Nanotechnology, 2020 Electric field enhancement in semiconductor nanostructures offers a possibility to find an alternative to the metallic particles which is well known for tuning the light-matter interaction due to its strong polarizability and size-dependent surface plasmon resonance energy. Raman spectroscopy is a powerful technique to monitor the electric field as its scattering depends on the electromagnetic eigenmode of the particle. Here, we observe enhanced polarized Raman scattering from germanium nanowires of different diameters. The incident electromagnetic radiation creates a distribution of the internal electric field inside the naowires which can be enhanced by manipulating the nanowire diameter, the incident electric field and its polarization. Our estimation of the enhancement factor, including its dependence on nanowire diameter, agrees well with the Mie theory for an infinite cylinder. Furthermore, depending on diameter and wavelength of incident radiation, polarized Raman study shows dipolar (antenna effect) and quadrupolar resonances, which has never been observed in germanium nanowire. We attempt to understand this polarized Raman behavior using COMSOL Multiphysics simulation, which suggests that the pattern observed is due to photon confinement within the nanowires. Thus, the light scattering direction can be toggled by tuning the polarization of incident excitation and diameter of non plasmonic nanowire.
Tailoring light-matter interaction in WS2-gold nanoparticles hybrid systems Tara Shankar Bhattacharya, Sreemanta Mitra, Shib Shankar Singha, Prasanna Kumar Mondal, Achintya Singha Physical Review B, 2019 Recently, considerable attention has been paid to tune the emission using hybrid systems composed of layered transition-metal dichalcogenides and metal nanoparticles (NPs) since metal NPs have the ability to enhance and localize the incident electromagnetic field. Furthermore, these hybrid systems show great interest from the standpoint of fundamental science as it constitutes an atomic scale prototype of charge-transfer complexes. Here, we realized ${\mathrm{WS}}_{2}$--gold (Au) NPs hybrids by chemically growing Au NPs at the edges of the mechanically exfoliated bilayer ${\mathrm{WS}}_{2}$. The Au NPs significantly increase the light-matter interaction which has been studied through Raman and photoluminescence (PL) spectroscopy. A substantial enhancement of the PL intensity in the ${\mathrm{WS}}_{2}$--Au composite concerning the pristine ${\mathrm{WS}}_{2}$ has been observed, and it increases as the number and size of the Au NPs on ${\mathrm{WS}}_{2}$ is increased. Geometry-dependent modification of plasmon resonance energy of Au NP alters the coupling strength between the emission pathways of ${\mathrm{WS}}_{2}$ and the plasmon which is manifested by a change in relative intensity between trion $({X}^{\ensuremath{-}})$ and exciton $(X)$ emissions. We probe the mechanism of the PL intensity modulation through polarization-dependent measurements and simulation. We have demonstrated that, in ${\mathrm{WS}}_{2}$, the internal quantum efficiency increases and activation energy decreases due to coupling with Au NPs. Compared to pristine ${\mathrm{WS}}_{2}$, a faster change in optical band gap with temperature in ${\mathrm{WS}}_{2}$--Au may be due to enhancing electron-phonon interaction and lattice expansion in the latter. Our paper indicates the possibility to develop high performance transition-metal dichalcogenide-based photonic devices.
Quadratic to linear magnetoresistance tuning in TmB4 Sreemanta Mitra, Jeremy Goh Swee Kang, John Shin, Jin Quan Ng, Sai Swaroop Sunku, Tai Kong, Paul C. Canfield, B. Sriram Shastry, Pinaki Sengupta, Christos Panagopoulos Physical Review B, 2019 The change of a material's electrical resistance (R) in response to an external magnetic field (B) provides subtle information for the characterization of its electronic properties and has found applications in sensor and storage related technologies. In good metals, Boltzmann's theory predicts a quadratic growth in magnetoresistance (MR) at low B and saturation at high fields. On the other hand, a number of nonmagnetic materials with weak electronic correlation and low carrier concentration for metallicity, such as inhomogeneous conductors, semimetals, narrow gap semiconductors and topological insulators, and two dimensional electron gas, show positive, nonsaturating linear magnetoresistance (LMR). However, observation of LMR in single crystals of a good metal is rare. Here we present low-temperature, angle-dependent magnetotransport in single crystals of the antiferromagnetic metal, ${\\mathrm{TmB}}_{4}$. We observe large, positive, and anisotropic MR(B), which can be tuned from quadratic to linear by changing the direction of the applied field. In view of the fact that isotropic, single crystalline metals with large Fermi surface (FS) are not expected to exhibit LMR, we attribute our observations to the anisotropic FS topology of ${\\mathrm{TmB}}_{4}$. Furthermore, the linear MR is found to be temperature independent, suggestive of quantum mechanical origin.
Area-driven Bosonic Superconductor-Insulator Transition in disordered Indium Oxide strips GC TEWARI, S Mitra, D Shahar Superconductor Science and Technology , 2026 2026
Correction to “Correlating Carrier Localization to Optoelectronic Behavior of Monolayer MoS 2 ” A Singha, A Parappurath, A Paul, SK Shetty, K Watanabe, T Taniguchi, ... ACS Applied Materials & Interfaces 17 (38), 54327-54327 , 2025 2025
Correlating Carrier Localization to Optoelectronic Behavior of Monolayer MoS 2 A Singha, A Parappurath, A Paul, SK Shetty, K Watanabe, T Taniguchi, ... ACS Applied Materials & Interfaces 17 (31), 44816-44824 , 2025 2025
Optical intensity driven mid-gap transitions in few-layer MoS2 T Bhattacharya, S Patra, S Singha, S Mitra, P Mahadevan, A Singha Physical Review B 111, 115412 , 2025 2025 Citations: 3
Interlayer Charge Transfer and Photodetection Efficiency of Graphene–Transition-Metal-Dichalcogenide Heterostructures A Parappurath, S Mitra, G Singh, NK Gill, T Ahmed, TP Sai, K Watanabe, ... Phys. Rev. Applied 17, 064062 , 2022 2022 Citations: 17
Graphene- WS2 van der Waals Hybrid Heterostructure for Photodetector and Memory Device Applications S Mitra, S Kakkar, T Ahmed, A Ghosh Phys. Rev. Appl. 14 (06), 064029 , 2020 2020 Citations: 21
Probing dipole and quadrupole resonance mode in non-plasmonic nanowire using Raman spectroscopy S Raha, S Mitra, PK Mondal, S Biswas, JD Holmes, A Singha Nanotechnology 31, 425201 , 2020 2020 Citations: 2
Tailoring phonon modes of few-layered MoS2 by in-plane electric field S Mitra, D Srivastava, SS Singha, S Dutta, B Satpati, M Karppinen, ... npj 2D Matererials and Applications 4, 6 , 2020 2020 Citations: 23
Tailoring light-matter interaction in WS2–gold nanoparticles hybrid systems TS Bhattacharya, S Mitra, SS Singha, PK Mondal, A Singha Physical Review B 100, 235438 , 2019 2019 Citations: 17
Quadratic to linear magnetoresistance tuning in TmB4 S Mitra, JGS Kang, J Shin, JQ Ng, SS Sunku, T Kong, PC Canfield, ... Phys. Rev. B 99, 045119 , 2019 2019 Citations: 20
Degeneracy of the 1/8 Plateau and Antiferromagnetic Phases in the Shastry-Sutherland Magnet TmB4 J Trinh, S Mitra, C Panagopoulos, T Kong, PC Canfield, AP Ramirez Phys. Rev. Lett. 121, 167203 , 2018 2018 Citations: 34
Negative Magnetoresistance in Amorphous Indium Oxide Wires S Mitra, GC Tewari, D Mahalu, D Shahar Scientific Reports 6, 37687 , 2016 2016 Citations: 16
Multifunctionality in graphene decorated with cobalt nanorods O Mondal, S Mitra, A Datta, D Chakravorty, M Pal Materials & Design 101, 204-209 , 2016 2016 Citations: 6
A brief review on graphene/inorganic nanostructure composites: materials for the future S Mitra, S Banerjee, A Datta, D Chakravorty Ind. J. Phys. 90, 1019 , 2016 2016 Citations: 45
Finite Size Effect in Amorphous Indium oxide S Mitra, GC Tewari, D Mahalu, D Shahar Phys. Rev. B 93, 155408 , 2016 2016 Citations: 12
Nonequilibrium Second-Order Phase Transition in a Cooper-Pair Insulator A Doron, I Tamir, S Mitra, G Zeltzer, M Ovadia, D Shahar Phys. Rev. Lett. 116, 057001 , 2016 2016 Citations: 18
Evidence for a finite-temperature insulator M Ovadia, D Kalok, I Tamir, S Mitra, B Sacépé, D Shahar Scientific reports 5 (1), 13503 , 2015 2015 Citations: 134
Reduced graphene oxide synthesis by high energy ball milling O Mondal, S Mitra, M Pal, A Datta, S Dhara, D Chakravorty Materials Chemistry and Physics 161, 123-129 , 2015 2015 Citations: 66
Sensing Behaviour of Some Nanocomposite Systems D Chakravorty, BN Pal, S Banerjee, A Mandal, S Mitra, DR Saha Soft Nanoscience Letters 3 (04), 12-15 , 2013 2013 Citations: 2
Dielectric relaxation studies on two-dimensional nanocomposites of NiS and Na-4 mica A Bose, A Mandal, S Mitra, SK De, S Banerjee, D Chakravorty Indian Journal of Physics 87 (10), 977-981 , 2013 2013 Citations: 8
MOST CITED SCHOLAR PUBLICATIONS
Evidence for a finite-temperature insulator M Ovadia, D Kalok, I Tamir, S Mitra, B Sacépé, D Shahar Scientific reports 5 (1), 13503 , 2015 2015 Citations: 134
Reduced graphene oxide synthesis by high energy ball milling O Mondal, S Mitra, M Pal, A Datta, S Dhara, D Chakravorty Materials Chemistry and Physics 161, 123-129 , 2015 2015 Citations: 66
Template based growth of nanoscaled films: a brief review S Mitra, A Mandal, S Banerjee, A Datta, S Bhattacharya, A Bose, ... Indian Journal of Physics 85 (5), 649-666 , 2011 2011 Citations: 59
Magnetodielectric effect in graphene-PVA nanocomposites S Mitra, O Mondal, DR Saha, A Datta, S Banerjee, D Chakravorty The Journal of Physical Chemistry C 115 (29), 14285-14289 , 2011 2011 Citations: 54
A brief review on graphene/inorganic nanostructure composites: materials for the future S Mitra, S Banerjee, A Datta, D Chakravorty Ind. J. Phys. 90, 1019 , 2016 2016 Citations: 45
Degeneracy of the 1/8 Plateau and Antiferromagnetic Phases in the Shastry-Sutherland Magnet TmB4 J Trinh, S Mitra, C Panagopoulos, T Kong, PC Canfield, AP Ramirez Phys. Rev. Lett. 121, 167203 , 2018 2018 Citations: 34
Tunneling conduction in graphene/(poly)vinayl alcohol composite S Mitra, S Banerjee, D Chakravorty Journal of Applied Physics 113 (15), 154314 , 2013 2013 Citations: 28
Tailoring phonon modes of few-layered MoS2 by in-plane electric field S Mitra, D Srivastava, SS Singha, S Dutta, B Satpati, M Karppinen, ... npj 2D Matererials and Applications 4, 6 , 2020 2020 Citations: 23
Graphene- WS2 van der Waals Hybrid Heterostructure for Photodetector and Memory Device Applications S Mitra, S Kakkar, T Ahmed, A Ghosh Phys. Rev. Appl. 14 (06), 064029 , 2020 2020 Citations: 21
Quadratic to linear magnetoresistance tuning in TmB4 S Mitra, JGS Kang, J Shin, JQ Ng, SS Sunku, T Kong, PC Canfield, ... Phys. Rev. B 99, 045119 , 2019 2019 Citations: 20
Nonequilibrium Second-Order Phase Transition in a Cooper-Pair Insulator A Doron, I Tamir, S Mitra, G Zeltzer, M Ovadia, D Shahar Phys. Rev. Lett. 116, 057001 , 2016 2016 Citations: 18
Observation of spin-glass behavior in nickel adsorbed few layer graphene S Mitra, O Mondal, S Banerjee, D Chakravorty Journal of Applied Physics 113 (2), 024307 , 2013 2013 Citations: 18
Interlayer Charge Transfer and Photodetection Efficiency of Graphene–Transition-Metal-Dichalcogenide Heterostructures A Parappurath, S Mitra, G Singh, NK Gill, T Ahmed, TP Sai, K Watanabe, ... Phys. Rev. Applied 17, 064062 , 2022 2022 Citations: 17
Tailoring light-matter interaction in WS2–gold nanoparticles hybrid systems TS Bhattacharya, S Mitra, SS Singha, PK Mondal, A Singha Physical Review B 100, 235438 , 2019 2019 Citations: 17
Negative Magnetoresistance in Amorphous Indium Oxide Wires S Mitra, GC Tewari, D Mahalu, D Shahar Scientific Reports 6, 37687 , 2016 2016 Citations: 16
Magnetodielectric effect in nickel nanosheet-Na-4 mica composites S Mitra, A Mandal, A Datta, S Banerjee, D Chakravorty EPL (Europhysics Letters) 92 (2), 26003 , 2010 2010 Citations: 15
Nanoindentation studies on silver nanoparticles D Chakravorty, P Boughton, DR Saha, MR Mada, S Mitra, A Mandal AIP Conference Proceedings , 2013 2013 Citations: 14
Finite Size Effect in Amorphous Indium oxide S Mitra, GC Tewari, D Mahalu, D Shahar Phys. Rev. B 93, 155408 , 2016 2016 Citations: 12
Multiphonon scattering and photoluminescence of two dimensional ZnS nanosheets grown within Na-4 mica A Mandal, S Mitra, A Datta, S Banerjee, S Dhara, D Chakravorty Journal of Applied Physics 112 (7) , 2012 2012 Citations: 9
Dielectric relaxation studies on two-dimensional nanocomposites of NiS and Na-4 mica A Bose, A Mandal, S Mitra, SK De, S Banerjee, D Chakravorty Indian Journal of Physics 87 (10), 977-981 , 2013 2013 Citations: 8
