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[4] Indirect excitons and many-body interactions in InGaAs double quantum wells, C. L. Smallwood, R. Owen, M. W. Day, T. Suzuki, R. Singh, T. M. Autry, S. Bhalerao, F. Jabeen, and S. T. Cundiff, Phys. Rev. B 112, 035305 (2025). DOI, Editor's suggestion.
[3] Quantitative line shape analysis for arbitrary inhomogeneity in two-dimensional coherent spectroscopy, B. De, P. Kumar, K. K. Maurya, R. Tripathi, and R. Singh, Opt. Lett. 50, 4502 (2025). DOI, Featured on Quantum Zeitgeist.
Two-dimensional coherent spectroscopy is widely used to quantify broadening mechanisms in materials. A common assumption made in this procedure is that a Gaussian distribution is assumed for the inhomogeneous broadening. In this work, we extend such quantitative analysis for an arbitrary inhomogeneous distribution. We have developed a simulation framework and fitting procedure that is demonstrated for an excitonic resonance with a non-Gaussian inhomogeneity.
[2] Coherent nonlinear optical response for high-intensity excitation, R. Tripathi, K. K. Maurya, P. Kumar, B. De, and R. Singh, J. Chem. Phys. 162, 114111 (2025). DOI, Special Collection: David Jonas Festschrift.
Coherent optical response of a material is important from the perspective of applications in quantum information. Two-dimensional coherent spectroscopy (2DCS) is a powerful technique to study such properties in a variety of systems. Such experiments are typically performed in relatively low-excitation regime, particularly due to theoretical limitations of interpreting the data for high-intensity excitation. Here, we have demonstrated a technique to perform exact calculations of 2D spectra even in the high-intensity regime. These simulations are used to model experiments performed on semiconductor nanostructures, both by us and previously reported results from other groups. These results are significant for the community of researchers performing spectroscopy with intense light.
[1] Exciton-exciton interaction: A quantitative comparison between complimentary phenomenological models, P. Kumar*, B. De*, R. Tripathi, and R. Singh, Phys. Rev. B 109, 155423 (2024). DOI (*equal contribution)
Exciton-exciton interactions play a pivotal role in shaping the optical properties of semiconductor nanostructures. In this work, we quantitatively compare two phenomenological models, which incorporate many-body interactions (MBIs) differently. As excitons are the bound pairs of electron-hole, one model treats them as fermions and the other as weakly interacting spin-one composite bosons. Both models yield similar results, as demonstrated through two-dimensional coherent spectroscopy simulations, despite their different treatments of MBIs. This research suggests a framework for comparing the relative strength of many-body interactions among various excitonic systems. It might also be applied to novel, condensed phases of excitons such as condensates and superfluids.
Pre-IISERB
Spectroscopic insights into high defect tolerance of Zn: CuInSe 2 quantum-dot-sensitized solar cells, J. Du, R. Singh, I. Fedin, A. S. Fuhr, and V. I. Klimov, Nat. Energy 5, 409 (2020). DOI, Featured on cover, LANL press release, Physics World
Hot-electron dynamics in quantum dots manipulated by spin-exchange Auger interactions, R. Singh, W. Liu, J. Lim, I. Robel, and V. I. Klimov, Nat. Nanotechnol. 14, 1035 (2019). DOI, LANL press release
Dephasing of InAs quantum dot p-shell excitons using two-dimensional coherent spectroscopy, T. Suzuki, R. Singh, G. Moody, M. Aβmann, M. Bayer, A. Ludwig, A. D. Wieck, and S. T. Cundiff, Phys. Rev. B 98, 1095304 (2018). DOI
Enhanced Multiple Exciton Generation in PbS|CdS Janus-like Heterostructured Nanocrystals, D. M. Kroupa, G. F. Pach, M. Vörös, F. Giberti, B. D. Chernomordik, R. W. Crisp, A. J. Nozik, J. C. Johnson, R. Singh, V. I. Klimov, G. Galli, and M. C. Beard, ACS Nano 12, 10084 (2018). DOI
Micromachining of Polyurethane Membranes for Tissue Engineering Applications, A. Arefin, Q. Mcculloch, R. Martinez, S. A. Martin, R. Singh, O. M. Ishak, E. M. Higgins, K. E. Haffey, J.-H. Huang, S. Iyer, P. Nath, R. Iyer, and J. F. Harris, ACS Biomater. Sci. Eng. 4 3522 (2018). DOI
Deconvolution of Optical Multidimensional Coherent Spectra, M. Richter, R. Singh, M. E. Siemens, and S. T. Cundiff, Sci. Adv. 4, eaar7697 (2018). DOI
Transient Spectroscopy of Glass-Embedded Perovskite Quantum Dots: Novel Structures in an Old Wrapping, O. V. Kozlov, R. Singh, B. Ai, J. Zhang, C. Liu, and V. I. Klimov, Z. Phys. Chem. 232, 1495 (2018). DOI
Detuning Dependence of Rabi Oscillations in an InAs Self-Assembled Quantum Dot Ensemble, T. Suzuki, R. Singh, M. Bayer, A. Ludwig, A. D. Wieck, and S. T. Cundiff, Phys. Rev. B 97, 161301(R) (2018). DOI, Selected as "Editor's suggestion"
Localization dynamics of excitons in disordered semiconductor quantum wells, R. Singh, M. Richter, G. Moody, M. E. Siemens, H. Li, and S. T. Cundiff, Phys. Rev. B 95, 237307 (2017). DOI
Coherent Control of the Exciton-Biexciton System in an InAs Self Assembled Quantum Dot Ensemble, T. Suzuki, R. Singh, M. Bayer, A. Ludwig, A. D. Wieck, and S. T. Cundiff, Phys. Rev. Lett. 117, 157402 (2016). DOI, Synopsis on Physics, Selected as "Editor's suggestion"
Polarization-dependent exciton linewidth in semiconductor quantum wells: A consequence of bosonic nature of excitons, R. Singh, T. Suzuki, T. M. Autry, G. Moody, M. E. Siemens, and S. T. Cundiff, Phys. Rev. B 94, 081304(R) (2016). DOI
Quantifying spectral diffusion by the direct measurement of the correlation function for excitons in semiconductor quantum wells, R. Singh, G. Moody, M. E. Siemens, H. Li, and S. T. Cundiff, J. Opt. Soc. Am. B 33, C137 (2016). DOI
Multi-dimensional coherent optical spectroscopy of semiconductor nanostructures: Collinear and non-collinear approaches, G. Nardin, T. M. Autry, G. Moody, R. Singh, H. Li, and S. T. Cundiff, J. Appl. Phys. 117, 112804 (2015). DOI
Coherent Coupling of Excitons and Trions in a Photoexcited CdTe/CdMgTe Quantum Well, G. Moody, I. A. Akimov, H. Li, R. Singh, D. R. Yakovlev, G. Karczewski, M. Wiater, T. Wojtowicz, M. Bayer, and S. T. Cundiff, Phys. Rev. Lett. 112, 097401 (2014). DOI
Coherent excitonic coupling in an asymmetric double InGaAs quantum well, G. Nardin, G. Moody, R. Singh, T. M. Autry, H. Li, F. Morier-Genoud, and S. T. Cundiff, Phys. Rev. Lett. 112, 046402 (2014). DOI
Biexcitons in semiconductor quantum dot ensembles, G. Moody, R. Singh, H. Li, I. A. Akimov, M. Bayer, D. Reuter, A. D. Wieck, A. S. Bracker, D. Gammon, and S. T. Cundiff, Phys. Status Solidi (b) 250, 1753 (2013). DOI
Anisotropic homogeneous linewidth of the heavy hole exciton in (110)-oriented GaAs quantum wells, R. Singh, T. M. Autry, G. Nardin, G. Moody, H. Li, K. Pierz, M. Bieler, and S. T. Cundiff, Phys. Rev. B 88, 045304 (2013). DOI
Correlation and dephasing effects on the non-radiative coherence between bright excitons in an InAs quantum dot ensemble measured with 2D spectroscopy, G. Moody, R. Singh, H. Li, I. A. Akimov, M. Bayer, D. Reuter, A. D. Wieck, and S. T. Cundiff, Solid State Commun. 163, 65 (2013). DOI
Fifth-order nonlinear optical response of excitonic states in an InAs quantum dot ensemble measured with 2D spectroscopy, G. Moody, R. Singh, H. Li, I. A. Akimov, M. Bayer, D. Reuter, A. D. Wieck, and S. T. Cundiff, Phys. Rev. B 87, 045313 (2013). DOI
Influence of confinement on biexciton binding in semiconductor quantum dot ensembles measured with 2D spectroscopy, G. Moody, R. Singh, H. Li, I. A. Akimov, M. Bayer, D. Reuter, A. D. Wieck, A. S. Bracker, D. Gammon, and S. T. Cundiff, Phys. Rev. B 87, 041304(R) (2013) DOI
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