Riyanka Karmakar
@iiserb.ac.in
Senior Research Fellow, Department of Physics, Indian Institute of Science Education and Research Bhopal, 462066 India
Department of Physics, Indian Institute of Science Education and Research Bhopal, 462066 India
Scopus Publications
Scholar Citations
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Scopus Publications
Naresh Chandra Maurya, Riyanka Karmakar, Rajesh Kumar Yadav, Pravrati Taank, Santu K. Bera, Anirban Mondal, Dipendranath Mandal, Megha Shrivastava, Md. Nur Hasan, Tuhin Kumar Maji,et al.
American Physical Society (APS)
Pravrati Taank, Riyanka Karmakar, and K. V. Adarsh
Wiley
Riyanka Karmakar, Dipendranath Mandal, Megha Shrivastava, and K. V. Adarsh
Optica Publishing Group
In this Letter, we report the third-order absorptive and refractive nonlinear optical response of highly luminescent WS2 quantum dots (QDs) in the off-resonant femtosecond and nanosecond pulses, which is beneficial for optical limiting and quantum information processing. For 800 nm femtosecond excitation, QDs show two-photon absorption (β = (107 ± 2)×10−3 cm/GW) with positive nonlinearity originating from bound carriers. This picture changes significantly for 532 nm nanosecond excitation, where it shows reverse saturable absorption with negative nonlinearity primarily originating from the sequential absorption of two single photons through the shallow defects, creating free carriers. Our results provide a promising route toward low-dimensional optoelectronic devices.
Pravrati Taank, Riyanka Karmakar, Rituraj Sharma, Rajesh Kumar Yadav, Megha Shrivastava, Naresh Chandra Maurya, Tuhin Kumar Maji, Debjani Karmakar, and K. V. Adarsh
American Chemical Society (ACS)
Riyanka Karmakar, Pravrati Taank, and K. V. Adarsh
AIP Publishing
Unravelling the qualitative descriptions of ultrafast energy relaxation dynamics in transition metal dichalcogenides (TMDCs) is very important for the fundamental understanding of the nature of photoexcited carriers. Herein, we discuss the temporal evolution of B-exciton dynamics of colloidal MoS2 few layers by using femtosecond transient pump-probe absorption spectroscopy. We observe trapped carrier hopping and bimolecular recombination, which is portrayed as phonon-assisted coalescence through indirect bandgap at lower carrier-density and an unconventional bottleneck in decay kinetics above a critical density (⁓ 40 × 1013 cm-2). Also, we propose a new model describing the mechanistic origin of dynamical characterization of exciton relaxation with unprecedented carrier-densitydependent phenomena. This model is feasible to explain the physics behind the obscured nature of quenching of photoluminescence quantum yield of TMDCs and will provide powerful insight for fabricating defect-free optoelectronic devices in the near future.
Riyanka Karmakar and K.V. Adarsh
Optica Publishing Group
Here, we studied the intriguing optical properties of WS2 quantum dots by various time-resolved spectroscopic techniques to get a comprehensive understanding of spectral and dynamical characteristics, specifically, we show long-lived ~ 95 ps trap-state emission.