Kamaraju Natarajan

@iiserkol.ac.in

Associate Professor and Department of Physical Sciences
Indian Institute of Science Education and Research Kolkata

Kamaraju Natarajan


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https://researchid.co/nkamaraju

RESEARCH, TEACHING, or OTHER INTERESTS

Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Acoustics and Ultrasonics, Materials Science
49

Scopus Publications

918

Scholar Citations

14

Scholar h-index

19

Scholar i10-index

Scopus Publications

  • Ultrafast dynamics of carriers, coherent acoustic phonons, and strain pulses in BiSbTe1.5Se1.5 topological insulator thin films
    Anupama Chauhan, Sidhanta Sahu, Poulami Ghosh, Dheerendra Singh, Sambhu G. Nath, Anjan Kumar N. M., P. K. Panigrahi, Chiranjib Mitra, N. Kamaraju
    Physical Review B, 2025
    Here, we investigate the ultrafast carriers, coherent acoustic phonons, and acoustic strain pulse dynamics in topological insulator ${\mathrm{BiSbTe}}_{1.5}{\mathrm{Se}}_{1.5}$ (BSTS) thin films of various thicknesses using degenerate pump-probe reflection spectroscopy. In this study, we have used sapphire as the main substrate since the BSTS-Sapphire interface has the maximum acoustic reflection in comparison to BSTS-GaAs, BSTS-Si, and BSTS-MgO interfaces. The transient reflectivity data for the films with thickness more than twice the penetration depth mainly contains the traveling acoustic strain pulses (TASP) and a single-exponential ($\ensuremath{\sim}2$ ps) electronic background whereas the data for the films with thickness less than penetration depth is dominated by coherent acoustic phonons (CAPs) and a biexponential electronic background of ${\ensuremath{\tau}}_{1}\ensuremath{\sim}2$ ps and ${\ensuremath{\tau}}_{2}\ensuremath{\sim}260--380$ ps. The experimentally observed TASP are reproduced by a well-known theoretical acoustic strain model. Further, to examine the underlying physics that is responsible for the dynamics of photoexcited carriers, CAPs and strain pulses, we have carried out carrier density and temperature dependent (7--294 K) studies on 22 nm and 192 nm thick BSTS films. For the 22 nm BSTS film, the two decay constants ${\ensuremath{\tau}}_{1}$ and ${\ensuremath{\tau}}_{2}$ increase with increase in carrier density at room temperature and decrease with increase in temperature at a carrier density of 1.7 $\ifmmode\times\else\texttimes\fi{}{10}^{19}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{\ensuremath{-}3}$, respectively. A closer inspection of the behavior of ${\ensuremath{\tau}}_{1}$ and ${\ensuremath{\tau}}_{2}$ with carrier density and temperature indicates that ${\ensuremath{\tau}}_{1}$ is due to the interplay of electron-phonon scattering and carrier diffusion whereas ${\ensuremath{\tau}}_{2}$ plausibly stems from the combination of defect-assisted and phonon-assisted recombination. Furthermore, with increasing temperature, there is an anharmonic decay induced softening of $\ensuremath{\sim}14%$ in the phonon frequency and $\ensuremath{\sim}48%$ anomalous decrease in the phonon damping parameter due to decreased scattering between the Dirac surface electrons and the acoustic phonons. Additionally, temperature-dependent studies on the 192 nm film reveal $\ensuremath{\sim}7%$ reduction in sound velocity, compared to $14%$ reduction in 22 nm film.
  • Revealing the magnetic dimensional crossover in the Heisenberg ferromagnet CrSiTe3 through picosecond strain pulses
    Anjan Kumar N M, Soumya Mukherjee, Abhirup Mukherjee, Ajinkya Punjal, Shubham Purwar, Thirupathaiah Setti, Shriganesh Prabhu S., Siddhartha Lal, N. Kamaraju
    Physical Review B, 2025
    Elucidating the emergence of long-range magnetic ordering from its precursor short-range magnetic ordering (SRMO) in two-dimensional van der Waals materials holds profound implications for fundamental research and technological advancements. However, directly observing the intricate stages of this magnetic dimensional crossover (MDC) remains a significant experimental challenge. While magnetoelastic coupling offers a promising avenue, detecting the minute lattice response to SRMO proves challenging. To meet this goal, we have executed an alternative approach by employing picosecond acoustic strain pulses generated by femtosecond lasers to probe the various stages of MDC through the magnetoelastic coupling. By analyzing the shape of the strain pulse in both the time and frequency domains as a function of temperature, we clearly demonstrate the detection of the subtle influence of spin fluctuations on the lattice. Additionally, the ultrafast carrier dynamics also show signatures of MDC. Our measurements pave the way toward characterizing magnetic materials in time-resolved experiments that are crucial in designing a new generation of spin-based optoelectronic devices.
  • Exploring the influence of magnetic order on phonon and electron dynamics in MnBi2Te4 and Sb doped MnBi2Te4 by time-domain THz spectroscopy
    Soumya Mukherjee, Anjan Kumar NM, Subhadip Manna, Sambhu G Nath, Radha Krishna Gopal, Chiranjib Mitra, N. Kamaraju
    International Conference on Infrared Millimeter and Terahertz Waves Irmmw Thz, 2025
    MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>, the first stoichiometric magnetic-topological insulator, has gained considerable attention for being able to demonstrate several novel phenomena of quantum physics at relatively higher temperatures. Here, an exhaustive investigation of the thin films of MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> and Sb doped MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> has been carried out using time-domain THz spectroscopy. The real THz conductivity displays prominent IR active E<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">u</inf> phonon mode (at ~1.5 THz) merged on top of the Drude-like background contributions from bulk and surface electrons. The extracted parameters from the Drude-Fano-Lorentz model fitting of THz conductivity data, displays change in their temperature dependence around the Neel temperature due to magnetic ordering. This further implies strong coupling between magnetic ordering and electronic band structure in MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf>. The Eu phonon frequency shows an anomalous blue-shift of ~ 0.1 THz (~7%) for MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> and ~0.2 THz (~13%) for Sb doped MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> as the temperatures increases in the range of 7 K and 250 K. The Eu phonon mode in Sb doped MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> shows asymmetric line-shape compared to that of MnBi2Te4, indicating the emergence of Fano interference between the phonons and the electrons due to the Sb doping. This also suggests that the relatively higher anomalous blue shift of phonons in Sb doped MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> arises from strong electron-phonon coupling. These measurements and analysis provide a comprehensive understanding of the electron and phonon dynamics of MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> and Sb doped MnBi<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>Te<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</inf> in the THz range.
  • Magnetic order influenced phonon and electron dynamics in MnBi2 Te4 and Sb-doped MnBi2 Te4 investigated by terahertz time-domain spectroscopy
    Soumya Mukherjee, Anjan Kumar N. M., Subhadip Manna, Sambhu G. Nath, Radha Krishna Gopal, Chiranjib Mitra, N. Kamaraju
    Physical Review B, 2024
    ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$, the first topological insulator with inherent magnetic ordering, has recently attracted significant attention for providing a platform to realize several exotic quantum phenomena at relatively higher temperatures. In this work, we have carried out an exhaustive investigation of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ and Sb-doped ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ thin films using THz time-domain spectroscopy. The extracted real THz conductivity displays a strong IR active ${\mathrm{E}}_{u}$ phonon absorption peak (at $\ensuremath{\sim}1.5$ THz) merged on top of the Drude-like contributions from bulk and surface electrons. The extracted parameters from the THz conductivity data fitted to the Drude-Fano-Lorentz model show significant changes in their temperature dependence around the magnetic ordering N\'eel temperature, which is suggestive of the coupling between magnetic ordering and electronic band structure. The frequency of the ${E}_{u}$ phonon displays an anomalous blueshift with increasing temperatures by $\ensuremath{\sim}0.1$ THz ($\ensuremath{\sim}7%$) for ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ and $\ensuremath{\sim}0.2$ THz ($\ensuremath{\sim}13%$) for Sb-doped ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ between 7 and 250 K. The line shape of the ${E}_{u}$ phonon mode in Sb-doped ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ shows significant Fano asymmetry compared to that of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$, indicating that Sb doping plays an important role in the Fano interference between the phonons and the electrons, in this system. These results indicate that the anomalous phonon behavior seen in ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ arises mainly from a positive cubic anharmonicity-induced self-energy parameter, whereas both anharmonicity and the electron phonon coupling are at play in making the relatively higher anomalous blueshift of phonons in Sb-doped ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$. Our studies provide a comprehensive understanding of the phonon and electron dynamics of ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ and Sb-doped ${\mathrm{MnBi}}_{2}{\mathrm{Te}}_{4}$ in the THz range using time-domain THz spectroscopy.
  • Probing Shallow and Deep Oxygen Traps in Binary Transition Metal Oxide, α-CoV2O6, Using Ultrafast Pump-Probe Spectroscopy
    Anjan Kumar N M, Soumya Mukherjee, Souvick Chakraborty, Ayan Mondal, Debabrata Samanta, Goutam Dev Mukherjee, Venkataramanan Mahalingam, Satyabrata Raj, N. Kamaraju
    Journal of Physical Chemistry C, 2024
    In this study, we have investigated the ultrafast carrier dynamics in the binary transition metal oxide, α- CoV2O6, using nondegenerate pump (3.14 eV)–probe (1.57 eV) transmission spectroscopy at room temperature. A detailed look at the time-resolved differential transmission data taken at various pump fluence excitations reveals the presence of two types of traps in the journey of photoexcited electrons: the shallow trap states and deep trap states. This finding is corroborated by steady-state absorption and photoluminescence spectra. First-principles density functional theory calculations reveal that these trap states originate from oxygen vacancies in α- CoV2O6. The empirical kinetic model consisting of these two trap states further indicates that the photoexcited electrons become trapped in these states on ultrafast timeframes: the trapping time in shallower traps is about 2 ps, whereas the capture time in deeper midgap traps takes about 30 ps. It further indicates that approximately 44% and 40% of the excited electrons are trapped in the shallow and midgap trap states, respectively, highlighting their crucial role in the optical properties of α- CoV2O6.
  • Trapping and exciton-exciton annihilation assisted ultrafast carrier dynamics in nanosheets of 2H-MoSe2 and Cr doped 1T/2H-MoSe2
    Soumya Mukherjee, Anjan Kumar NM, Ayan Mondal, Venkataramanan Mahalingam, N. Kamaraju
    Journal of Chemical Physics, 2023
    Nanosheets of transition metal dichalcogenides with prospects of photocatalysis and optoelectronics applications have significant potential in device fabrication due to their low-cost production and easily controllable morphology. Here, non-degenerate pump-probe differential transmission studies with varying pump-fluence have been carried out on single-phase 2H–MoSe2 and mixed-phase 1T/2H–MoSe2 nanosheets to characterize their excited carrier dynamics. For both the samples, the differential probe transmission data show photo-induced bleaching at earlier pump-probe delay followed by photo-induced absorption unveiling signatures of exciton-state filling, exciton trapping, defect-mediated photo-induced probe absorption and recombination of defect bound excitons. The exciton trapping and photo-induced absorption by the trapped-carriers are estimated to occur with time constant of ∼430 to 500 fs based on multi-exponential modelling of the differential transmission till pump-probe delay of ∼3.5 ps. Biexponential modeling of the subsequent slow-recovery of the negative differential transmission at pump-probe delay ≳3.5 ps reveals that the exciton recombination happens via two distinct decay channels with ∼25 to 55 ps (τ1) and ≳1 ns (τ2) time constants. Pump-fluence dependent reduction in τ1 and further modelling of exciton population using higher order kinetic rate equation reveals that the two-body exciton-exciton annihilation governs the exciton recombination initially with a decay rate of ∼10−8 cm3s−1. The detailed analysis suggests that the fraction of total excitons that decay via long decay channel decreases with increasing exciton density for 2H–MoSe2, in contrast to 1T/2H–MoSe2 where the fraction of excitons decaying via long decay channel remains constant.
  • Many-Body Interaction Governs the Ultrafast Relaxation Dynamics of Hot Holes in CuS Nanoflakes and Photocatalytic Efficiency-Enhanced CuS/Ag2S Nanocomposites
    Soumya Mukherjee, Anjan Kumar NM, Saranya Ramesh, B. Karthikeyan, N. Kamaraju
    ACS Applied Optical Materials, 2023
    A detailed nondegenerate ultrafast pump-probe transmission study of CuS nanoflakes and CuS/Ag 2 S nanocomposites with varying pump fluences is conducted in this work. The measured transient transmission data for CuS are found to originate from a strong photoinduced bleaching of intrinsic holes and a weaker photoinduced absorption of excited electrons. First-order decay-based multiexponential modeling of transient transmission data for CuS reveals three hole decay channels (∼240–410 fs, ∼24–144 ps, ≳10 μs) along with the electron decay channel of ∼1.0–2.6 ps, whereas for CuS/Ag 2 S, the weaker electron decay channel disappears due to the localization of hot electrons in the conduction band of Ag 2 S and an additional hole decay channel appears, making a total of four decay channels for the holes (∼230–470 fs, ∼10–49 ps, ≳10 μs, ∼132–326 ps). When the pump fluence is varied, these decay time constants are found to change considerably, indicating the presence of higher-order decay processes, which must be considered in the theoretical modeling of the decay of excited carriers. Therefore, we have modeled the time evolution of hot hole density using the empirical kinetic rate equation and extracted the higher-order rate constants. Both the second- and third-order rate constants are found to be almost one order lesser for CuS/Ag 2 S, compared to those of CuS, indicating that the overall decay process is getting slower for CuS/Ag 2 S, causing enhanced photocatalytic activity.
  • Investigation of conductivity and shielding efficiency of the free-standing PVA–GO–Ag composite thin films in terahertz regime using time-domain terahertz spectroscopy
    Soumya Mukherjee, N. M. Anjan Kumar, B. Karthikeyan, N. Kamaraju
    Applied Physics A Materials Science and Processing, 2023
  • Photoexcited Ultrafast Dynamics of Free Carriers and Polarons in V2O5Microparticles through Time-Resolved Nondegenerate Pump Probe Spectroscopy
    Anjan Kumar N M, Soumya Mukherjee, Saranya Ramesh, Ayan Mondal, Venkataramanan Mahalingam, N. Kamaraju
    Journal of Physical Chemistry C, 2022
    The photoexcited free carrier dynamics in V2O5 microparticles are studied using time-resolved nondegenerate pump–probe transmission spectroscopy. By employing a numerically solved polaronic kinetic model on the time-resolved absorption obtained from transmission data, the self-trapping of free carriers, i.e., formation of polarons, and the self-trap assisted bimolecular decay in V2O5 microparticles are investigated. Also, by performing the fluence-dependent experiments, the variation of the various processes with the photoexcited carrier density is understood by invoking the carrier screening effect. It is estimated from this work that the average density of polarons is ∼2.58 × 1017cm–3, with their formation time of ∼4.5 ps.
  • Investigation of self-trapped excitonic dynamics in hematite nanoforms through non-degenerate pump-probe transmission spectroscopy
    Anjan Kumar N M, Soumya Mukherjee, Anoop Sunny, B. Karthikeyan, N. Kamaraju
    Applied Physics Letters, 2022
    Non-degenerate pump–probe transmission spectroscopy is used to examine the ultrafast dynamics of photo-excited carriers in hematite nanoforms at various pump fluences. Using coupled rate equations, the kinetics of self-trapped exciton (STE) formation and its interaction with free excitons resulting in exciton annihilation were studied. It is shown from this model that the majority of the excitons were trapped by polaronic trap states to form self-trapped excitons within ∼3.5 ps. The findings indicate that free excitons and STEs interact non-linearly, similar to trap-assisted bi-molecular Auger recombination to annihilate one another. It is observed that there is substantial dependence of kinetics of STE formation and exciton decay on photo-excited exciton density, and the nature of this dependence indicates the reduced screening of electron–phonon interaction. Using the screening model applied to the rate constants of STE formation and decay, we estimate the saturation exciton density to be ∼3.3 × 1017 cm−3 and the average STE density to be ∼3.8 × 1018 cm−3 in the hematite nanoforms. We also noticed that doping K and Ni to hematite nanoforms up to 5% did not remarkably change the nature of the exciton dynamics.
  • A review on numerical methods for thickness determination in terahertz time-domain spectroscopy
    Soumya Mukherjee, N. M. Anjan Kumar, Prashanth C. Upadhya, N. Kamaraju
    European Physical Journal Special Topics, 2021
  • Ultrafast Carrier Dynamics of Undoped and Ho3+-Doped α-Bismuth Oxide Microrods
    Jit Sarkar, Shankar G. Menon, N. Prasad, B. Karthikeyan, N. Kamaraju
    Journal of Physical Chemistry C, 2019
  • Ultrafast electron hole plasma dynamics in chemically pristine and Ag-doped ZnO nanorods
    Jit Sarkar, Shankar G. Menon, C. Madhumitha, B. Karthikeyan, N. Kamaraju
    Journal of Applied Physics, 2018
  • Magnetoelastoelectric coupling in core-shell nanoparticles enabling directional and mode-selective magnetic control of THz beam propagation
    Moumita Dutta, Kamaraju Natarajan, Soutik Betal, Rohit P. Prasankumar, Amar S. Bhalla, Ruyan Guo
    Nanoscale, 2017
  • Transient GaAs plasmonic metasurfaces at terahertz frequencies
    Yuanmu Yang, N. Kamaraju, Salvatore Campione, Sheng Liu, John L. Reno, Michael B. Sinclair, Rohit P. Prasankumar, Igal Brener
    ACS Photonics, 2017
  • Ultrafast dynamics of epsilon-near-zero modes in GaAs at terahertz frequencies
    Yuanmu Yang, Kamaraju Natarajan, Salvatore Campione, Sheng Liu, John Reno, Rohit P. Prasankumar, Igal Brener
    2016 Conference on Lasers and Electro Optics CLEO 2016, 2016
  • Dynamic evolution of a two-dimensional electron gas in a magnetic field after optical photoexcitation
    N. Kamaraju, W. Pan, J. Reno, Q. Zhang, Junichiro Kono, A. J. Taylor, R. P. Prasankumar
    2016 Conference on Lasers and Electro Optics CLEO 2016, 2016
  • Using terahertz pulses to shed new light on quantum materials
    P. Bowlan, N. Kamaraju, D. A. Yarotski, A. J. Taylor, R. P. Prasankumar
    International Conference on Infrared Millimeter and Terahertz Waves Irmmw Thz, 2016
  • Dynamic evolution of a two-dimensional electron gas in a magnetic field after optical photoexcitation
    Kamaraju Natarajan, Qi Zhang, Michael R. Williams, Wei Pan, John L Reno, Junichiro Kono, Antionette Taylor, Rohit Prasankumar
    Optics Infobase Conference Papers, 2016
  • Ultrafast Dynamics of Epsilon-Near-Zero Modes in GaAs at Terahertz Frequencies
    Optics Infobase Conference Papers, 2016
  • Dynamic evolution of a two-dimensional electron gas in a magnetic field after optical photoexcitation
    Optics Infobase Conference Papers, 2016
  • Terahertz magneto-optical spectroscopy of two-dimensional hole and electron systems
    Conference on Lasers and Electro Optics Europe Technical Digest, 2015
  • Terahertz magneto-optical spectroscopy of two-dimensional hole and electron systems
    Kamaraju Natarajan, Wei Pan, Ulf Ekenberg, Dejan M Gvozdić, stephane Boubanga-Tombet, Prashanth C Upadhya, John Reno, Antoinette J. Taylor, Rohit P. Prasankumar
    CLEO QELS Fundamental Science CLEO QELS 2015, 2015
  • Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
    N. Kamaraju, W. Pan, U. Ekenberg, D. M. Gvozdić, S. Boubanga-Tombet, P. C. Upadhya, J. Reno, A. J. Taylor, R. P. Prasankumar
    Applied Physics Letters, 2015
  • Application of plasma-wave detectors for ultra-short pulse terahertz radiation
    A. Gutin, A. V. Muraviev, N. Kamaraju, X. Shen, Y. Yamaguchi, M. S. Shur, D. But, N. Dyakonova, W. Knap, S. Rudin, G. Rupper
    International Conference on Infrared Millimeter and Terahertz Waves Irmmw Thz, 2014
  • Indication of Te segregation in laser-irradiated ZnTe observed by in situ coherent-phonon spectroscopy
    Toru Shimada, N. Kamaraju, Christian Frischkorn, Martin Wolf, Tobias Kampfrath
    Applied Physics Letters, 2014
  • Subcycle control of terahertz waveform polarization using all-optically induced transient metamaterials
    Kan Wu, Javier García de Abajo, Cesare Soci, Perry Ping Shum, Nikolay I Zheludev
    Light Science and Applications, 2014
  • Subcycle control of terahertz waveform polarization using all-optically induced transient metamaterials
    N Kamaraju, Andrea Rubano, Linke Jian, Surajit Saha, T Venkatesan, Jan Nötzold, R Kramer Campen, Martin Wolf, Tobias Kampfrath
    Light Science and Applications, 2014
  • Asymmetric backscattering of ultraviolet light by low-refractive index thin film of tilted alumina nanorods
    CLEO QELS Fundamental Science CLEO QELS Fs 2013, 2013
  • Asymmetric backscattering of ultraviolet light by low- refractive index thin film of tilted alumina nanorods
    CLEO Science and Innovations CLEO Si 2013, 2013
  • Asymmetric backscattering of ultraviolet light by low-refractive index thin film of tilted alumina nanorods
    Xing Yan, Kamaraju Natarajan, Tanuj Saxena, Michael S. Shur
    2013 Conference on Lasers and Electro Optics CLEO 2013, 2013
  • Femtosecond photoexcited carrier dynamics in reduced graphene oxide suspensions and films
    SUNIL KUMAR, N. KAMARAJU, K. S. VASU, A. K. SOOD
    International Journal of Nanoscience, 2011
  • Ultrafast dynamics of gold nanorods: Tuning between photo-bleaching and photo-induced absorption
    M. ANIJA, SUNIL KUMAR, N. KAMARAJU, NEHA TIWARI, S. K. KULKARNI, A. K. SOOD
    International Journal of Nanoscience, 2011
  • Coherent phonons in pyrochlore titanates A2Ti2O 7 (A= Dy, Gd, Tb): A phase transition in Dy2Ti 2O7 at 110 K
    N. Kamaraju, Sunil Kumar, Surajit Saha, Surjeet Singh, R. Suryanarayanan, A. Revcolevschi, A. K. Sood
    Physical Review B Condensed Matter and Materials Physics, 2011
  • Large-amplitude chirped coherent phonons in tellurium mediated by ultrafast photoexcited carrier diffusion
    N. Kamaraju, Sunil Kumar, M. Anija, A. K. Sood
    Physical Review B Condensed Matter and Materials Physics, 2010
  • Temperature-dependent chirped coherent phonon dynamics in Bi 2Te3 using high-intensity femtosecond laser pulses
    N. Kamaraju, Sunil Kumar, A. K. Sood
    Europhysics Letters, 2010
  • Graphene analogue BCN: Femtosecond nonlinear optical susceptibility and hot carrier dynamics
    Sunil Kumar, N. Kamaraju, K.S. Vasu, Angshuman Nag, A.K. Sood, C.N.R. Rao
    Chemical Physics Letters, 2010
  • Terahertz Spectroscopy of Single-Walled Carbon Nanotubes in a Polymer Film: Observation of Low-Frequency Phonons
    Sunil Kumar, N. Kamaraju, B. Karthikeyan, M. Tondusson, E. Freysz, A. K. Sood
    Journal of Physical Chemistry C, 2010
  • Direct observation of low frequency confined acoustic phonons in silver nanoparticles: Terahertz time domain spectroscopy
    Sunil Kumar, N. Kamaraju, B. Karthikeyan, M. Tondusson, E. Freysz, A. K. Sood
    Journal of Chemical Physics, 2010
  • Influence of two photon absorption induced free carriers on coherent polariton and phonon generation in ZnTe crystals
    N. Kamaraju, Sunil Kumar, Eric Freysz, A. K. Sood
    Journal of Applied Physics, 2010
  • Terahertz time domain spectroscopy to detect low-frequency vibrations of double-walled carbon nanotubes
    Sunil Kumar, Natrajan Kamaraju, Alexander Moravsky, R. O. Loutfy, Marc Tondusson, Eric Freysz, Ajay Kumar Sood
    European Journal of Inorganic Chemistry, 2010
  • Femtosecond carrier dynamics and saturable absorption in graphene suspensions
    Sunil Kumar, M. Anija, N. Kamaraju, K. S. Vasu, K. S. Subrahmanyam, A. K. Sood, C. N. R. Rao
    Applied Physics Letters, 2009
  • Double walled carbon nanotubes as ultrafast optical switches
    N. Kamaraju, Sunil Kumar, Y. A. Kim, T. Hayashi, H. Muramatsu, M. Endo, A. K. Sood
    Applied Physics Letters, 2009
  • Ultrafast switching time and third order nonlinear coefficients of Microwave treated single walled carbon nanotube suspensions
    N. Kamaraju, Sunil Kumar, B. Karthikeyan, Bhalchandra Kakade, VijayamohananK. Pillai, A. K. Sood
    Journal of Nanoscience and Nanotechnology, 2009
  • Ultrafast electron dynamics and cubic optical nonlinearity of freestanding thin film of double walled carbon nanotubes
    N. Kamaraju, Sunil Kumar, B. Karthikeyan, Alexander Moravsky, R. O. Loutfy, A. K. Sood
    Applied Physics Letters, 2008
  • Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond z-scan measurements
    N. Kamaraju, Sunil Kumar, A. K. Sood, Shekhar Guha, Srinivasan Krishnamurthy, C. N. R. Rao
    Applied Physics Letters, 2007
  • Probing isolated bundles of single walled carbon nanotubes using bilayer interference enhanced Raman scattering
    N. Kamaraju, S. Balaji, D.V.S. Muthu, S. Mohan, A.K. Sood
    Chemical Physics Letters, 2006
  • Raman scattering in CaFeO3 and La0.33Sr0.67FeO3 across the charge-disproportionation phase transition
    Shankar Ghosh, N. Kamaraju, M. Seto, A. Fujimori, Y. Takeda, S. Ishiwata, S. Kawasaki, M. Azuma, M. Takano, A. K. Sood
    Physical Review B Condensed Matter and Materials Physics, 2005
  • Observation of narrow fluorescence from doubly driven four-level atoms at room temperature
    U. K Khan, J Sebastian, N Kamaraju, A Narayanan, R Srinivasan, H Ramachandran
    Europhysics Letters, 2004

RECENT SCHOLAR PUBLICATIONS

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    2025
  • Ultrafast Dynamics of Spin-Orbit Entangled Excitons Coupled to Magnetic Ordering in van der Waals Antiferromagnet NiPS3
    S Sahu, A Chauhan, P Ghosh, S Routh, R Puranik, S Thirupathaiah, S Lal, ...
    arXiv preprint arXiv:2509.04900 , 2025
    2025
    Citations: 1
  • Exploring the influence of magnetic order on phonon and electron dynamics in MnBi 2 Te 4 and Sb doped MnBi 2 Te 4 by time-domain THz spectroscopy
    S Mukherjee, AK NM, S Manna, SG Nath, RK Gopal, C Mitra, N Kamaraju
    2025 50th International Conference on Infrared, Millimeter, and Terahertz … , 2025
    2025
  • Ultrafast dynamics of carriers, coherent acoustic phonons, and strain pulses in topological insulator thin films
    A Chauhan, S Sahu, P Ghosh, D Singh, SG Nath, A Kumar NM, ...
    Physical Review B 112 (5), 054311 , 2025
    2025
    Citations: 1
  • Revealing the magnetic dimensional crossover in the Heisenberg ferromagnet CrSiTe3 through picosecond strain pulses
    ANM Kumar, S Mukherjee, A Mukherjee, A Punjal, S Purwar, T Setti, ...
    PHYSICAL REVIEW B 111 (14) , 2025
    2025
  • Revealing the magnetic dimensional crossover in the Heisenberg ferromagnet through picosecond strain pulses
    AK NM, S Mukherjee, A Mukherjee, A Punjal, S Purwar, T Setti, ...
    Physical Review B 111 (14), L140414 , 2025
    2025
    Citations: 2
  • Magnetic order influenced phonon and electron dynamics in and Sb-doped investigated by terahertz time-domain spectroscopy
    S Mukherjee, AK NM, S Manna, SG Nath, RK Gopal, C Mitra, N Kamaraju
    Physical Review B 110 (19), 195401 , 2024
    2024
    Citations: 7
  • Probing Shallow and Deep Oxygen Traps in Binary Transition Metal Oxide, alpha-CoV 2 O 6 , Using Ultrafast Pump-Probe Spectroscopy
    NM Kumar, S Mukherjee, S Chakraborty, A Mondal, D Samanta, ...
    JOURNAL OF PHYSICAL CHEMISTRY C 128 (35), 14717-14725 , 2024
    2024
  • Probing Shallow and Deep Oxygen Traps in Binary Transition Metal Oxide, α-CoV 2 O 6 , Using Ultrafast Pump–Probe Spectroscopy
    AK NM, S Mukherjee, S Chakraborty, A Mondal, D Samanta, ...
    The Journal of Physical Chemistry C 128 (35), 14717-14725 , 2024
    2024
    Citations: 2
  • Investigation of magnetic order influenced phonon and electron dynamics in MnBi Te and Sb doped MnBi Te through terahertz time-domain spectroscopy
    S Mukherjee, AK NM, S Manna, SG Nath, RK Gopal, C Mitra, N Kamaraju
    arXiv preprint arXiv:2403.11580 , 2024
    2024
    Citations: 1
  • Probing of magnetic dimensional crossover in CrSiTe through picosecond strain pulses
    S Mukherjee, A Mukherjee, A Punjal, S Purwar, T Setti, S Lal, N Kamaraju
    arXiv preprint arXiv:2402.01256 , 2024
    2024
  • Trapping and exciton-exciton annihilation assisted ultrafast carrier dynamics in nanosheets of 2H–MoSe2 and Cr doped 1T/2H–MoSe2
    S Mukherjee, AK Nm, A Mondal, V Mahalingam, N Kamaraju
    The Journal of Chemical Physics 159 (16) , 2023
    2023
    Citations: 1
  • Many-Body Interaction Governs the Ultrafast Relaxation Dynamics of Hot Holes in CuS Nanoflakes and Photocatalytic Efficiency-Enhanced CuS/Ag 2 S …
    S Mukherjee, AK NM, S Ramesh, B Karthikeyan, N Kamaraju
    ACS Applied Optical Materials 1 (7), 1332-1342 , 2023
    2023
    Citations: 3
  • Investigation of conductivity and shielding efficiency of the free-standing PVA–GO–Ag composite thin films in terahertz regime using time-domain terahertz spectroscopy
    S Mukherjee, NM Anjan Kumar, B Karthikeyan, N Kamaraju
    Applied Physics A 129 (5), 343 , 2023
    2023
    Citations: 6
  • Photoexcited Ultrafast Dynamics of Free Carriers and Polarons in V 2 O 5 Microparticles through Time-Resolved Nondegenerate Pump Probe Spectroscopy
    AK NM, S Mukherjee, S Ramesh, A Mondal, V Mahalingam, N Kamaraju
    The Journal of Physical Chemistry C 126 (48), 20535-20541 , 2022
    2022
    Citations: 4
  • Investigation of self-trapped excitonic dynamics in hematite nano-forms through non-degenerate pump-probe transmission spectroscopy
    NK Anjan Kumar N M, Soumya Mukherjee, Anoop Sunny, B. Karthikeyan
    Applied Physics Letters 121 (20), 202102 , 2022
    2022
    Citations: 2
  • A review on numerical methods for thickness determination in terahertz time-domain spectroscopy
    S Mukherjee, NMA Kumar, PC Upadhya, N Kamaraju
    The European Physical Journal Special Topics 230 (23), 4099-4111 , 2021
    2021
    Citations: 14
  • Ultrafast Carrier Dynamics of Undoped and Ho3+- Doped α-Bismuth Oxide Micro-Rods
    NK Jit Sarkar, Shankar G Menon, Neena Prasad, Karthikeyan Balasubramanian
    J. Phys. Chem. C 123, 10007−10012 , 2019
    2019
    Citations: 9

MOST CITED SCHOLAR PUBLICATIONS

  • Femtosecond carrier dynamics and saturable absorption in graphene suspensions
    S Kumar, M Anija, N Kamaraju, KS Vasu, KS Subrahmanyam, AK Sood, ...
    Applied physics letters 95 (19) , 2009
    2009
    Citations: 260
  • Large nonlinear absorption and refraction coefficients of carbon nanotubes estimated from femtosecond z-scan measurements
    N Kamaraju, S Kumar, AK Sood, S Guha, S Krishnamurthy, CNR Rao
    Applied Physics Letters 91 (25) , 2007
    2007
    Citations: 95
  • Raman scattering in and across the charge-disproportionation phase transition
    S Ghosh, N Kamaraju, M Seto, A Fujimori, Y Takeda, S Ishiwata, ...
    Physical Review B—Condensed Matter and Materials Physics 71 (24), 245110 , 2005
    2005
    Citations: 71
  • Subcycle control of terahertz waveform polarization using all-optically induced transient metamaterials
    N Kamaraju, A Rubano, L Jian, S Saha, T Venkatesan, J Nötzold, ...
    Light: Science & Applications 3 (2), e155-e155 , 2014
    2014
    Citations: 61
  • Transient GaAs Plasmonic Metasurfaces at Terahertz Frequencies
    IB Yuanmu Yang, N. Kamaraju, Salvatore Campione, Sheng Liu, John L. Reno ...
    ACS Photonics , 2016
    2016
    Citations: 51
  • Temperature-dependent chirped coherent phonon dynamics in Bi 2 Te 3 using high-intensity femtosecond laser pulses
    N Kamaraju, S Kumar, AK Sood
    EPL (Europhysics Letters) 92 (4), 47007 , 2010
    2010
    Citations: 42
  • Graphene analogue BCN: Femtosecond nonlinear optical susceptibility and hot carrier dynamics
    S Kumar, N Kamaraju, KS Vasu, A Nag, AK Sood, CNR Rao
    Chemical Physics Letters 499 (1-3), 152-157 , 2010
    2010
    Citations: 40
  • Terahertz spectroscopy of single-walled carbon nanotubes in a polymer film: observation of low-frequency phonons
    S Kumar, N Kamaraju, B Karthikeyan, M Tondusson, E Freysz, AK Sood
    The Journal of Physical Chemistry C 114 (29), 12446-12450 , 2010
    2010
    Citations: 34
  • Large-amplitude chirped coherent phonons in tellurium mediated by ultrafast photoexcited carrier diffusion
    N Kamaraju, S Kumar, M Anija, AK Sood
    Physical Review B—Condensed Matter and Materials Physics 82 (19), 195202 , 2010
    2010
    Citations: 31
  • Double walled carbon nanotubes as ultrafast optical switches
    N Kamaraju, S Kumar, YA Kim, T Hayashi, H Muramatsu, M Endo, ...
    Applied Physics Letters 95 (8) , 2009
    2009
    Citations: 31
  • Ultrafast electron dynamics and cubic optical nonlinearity of freestanding thin film of double walled carbon nanotubes
    N Kamaraju, S Kumar, B Karthikeyan, A Moravsky, RO Loutfy, AK Sood
    Applied Physics Letters 93 (9) , 2008
    2008
    Citations: 21
  • Terahertz Time Domain Spectroscopy to Detect Low‐Frequency Vibrations of Double‐Walled Carbon Nanotubes
    S Kumar, N Kamaraju, A Moravsky, RO Loutfy, M Tondusson, E Freysz, ...
    European Journal of Inorganic Chemistry 2010 (27), 4363-4366 , 2010
    2010
    Citations: 16
  • A review on numerical methods for thickness determination in terahertz time-domain spectroscopy
    S Mukherjee, NMA Kumar, PC Upadhya, N Kamaraju
    The European Physical Journal Special Topics 230 (23), 4099-4111 , 2021
    2021
    Citations: 14
  • Terahertz magneto-optical spectroscopy of a two-dimensional hole gas
    N Kamaraju, W Pan, U Ekenberg, DM Gvozdić, S Boubanga-Tombet, ...
    Applied Physics Letters 106 (3) , 2015
    2015
    Citations: 14
  • Indication of Te segregation in laser-irradiated ZnTe observed by in situ coherent-phonon spectroscopy
    TK Toru Shimada , Christian Frischkorn , Martin Wolf
    Applied Physics Letters , 2014
    2014
    Citations: 14
  • Coherent phonons in pyrochlore titanates O ( Dy, Gd, Tb): A phase transition in Dy Ti O at 110 K
    N Kamaraju, S Kumar, S Saha, S Singh, R Suryanarayanan, ...
    Physical Review B—Condensed Matter and Materials Physics 83 (13), 134104 , 2011
    2011
    Citations: 14
  • Magnetoelastoelectric coupling in core-shell nanoparticles enabling directional and mode-selective magnetic control of THz beam propagation
    ABRG Moumita Dutta, Kamaraju Natarajan, Soutik Betal, Rohit P. Prasankumar
    RSC Nanoscale 9 (35), 13052-13059 , 2017
    2017
    Citations: 12
  • Influence of two photon absorption induced free carriers on coherent polariton and phonon generation in ZnTe crystals
    N Kamaraju, S Kumar, E Freysz, AK Sood
    Journal of Applied Physics 107 (10) , 2010
    2010
    Citations: 12
  • Direct observation of low frequency confined acoustic phonons in silver nanoparticles: Terahertz time domain spectroscopy
    S Kumar, N Kamaraju, B Karthikeyan, M Tondusson, E Freysz, AK Sood
    The Journal of chemical physics 133 (1) , 2010
    2010
    Citations: 10
  • Ultrafast Carrier Dynamics of Undoped and Ho3+- Doped α-Bismuth Oxide Micro-Rods
    NK Jit Sarkar, Shankar G Menon, Neena Prasad, Karthikeyan Balasubramanian
    J. Phys. Chem. C 123, 10007−10012 , 2019
    2019
    Citations: 9