arXiv subjects

Sucharita Giri

Publications and source records attributed to Sucharita Giri.

7 recordsLinked to original sources

arXiv2025

Nonlinear Optical Spectroscopy of Nodal-Line Semimetals

Intense laser-driven nonlinear optical phenomena in two-dimensional (2D) nodal-line semimetals (NLS) exhibit complex mechanisms, particularly in the NbSi$_{x}$Te$_{2}$ material systems characterized by nonsymmorphic symmetry-protected band degeneracy. Our findings reveal how nonsymmorphic symmetry-protected band degeneracy fundamentally influences the material's nonlienar optical responses. Notably, the nonsymmorphic glide-mirror symmetry leads to the exclusive generation of odd-order harmonics from inversion-symmetry-broken NLS. Moreover, harmonics are emitted parallel and perpendicular to the driving laser's polarization. We demonstrate distinct generation mechanisms arise from intrachain and interchain processes, with their relative contributions varying significantly with the polarization of the driving laser pulse. The polarization-dependence exhibits two-fold anisotropy, with each harmonic order showing characteristic angular distributions of maximum yield. Additionally, our analysis of the ellipticity-dependence reveals an intricate interplay between interband and intraband mechanisms. These insights open new possibilities for controlling harmonic generation through precise tuning parameters of the driving laser and highlight the potentials of NLS materials to fabricate lightwave-based photonics, optoelectronic and quantum devices operating on ultrafast timescales.

physics.optics↗

arXiv2025

Inducing And Probing Charge Migration In Molecular Systems

Technological advancements in generation of ultrafast and intense laser pulses have enabled the real-time observation and control of charge migration in molecules on their natural timescale, which ranges from few femtoseconds to several hundreds of attoseconds. Present thesis discusses the effect of symmetry on the adiabatic attosecond charge migration in different molecular systems. The spatial representation of the charge migration is documented by time-dependent electronic charge and flux densities. Furthermore, the induced charge migration is imaged via time resolved x-ray diffraction (TRXD) with atomic-scale spatiotemporal resolution in few cases.

physics.optics↗

arXiv2023

Charge Migration in Heterocyclic Five-Membered Rings

This contribution presents numerical simulations of N-electron dynamics in heterocyclic five-membered ring molecules to shed light on the effect of molecular symmetry on charge migration. Laser-driven dynamics is studied using the hybrid time-dependent density functional theory/configuration methodology, and the ensuing field-free charge migration is investigated by means of transient electronic flux density maps. Our results demonstrate that the charge migration in aromatic rings is sensitive to the presence of heteroatoms such as oxygen and nitrogen. Their presence within the ring induces significant modifications of the character in the ground and low-lying electronic states, which is imprinted in the charge migration mechanism.

physics.atom-ph↗

arXiv2022

Probing the Effect of Molecular Structure Saddling on Ultrafast Charge Migration via Time-Resolved X-ray Diffraction

Metal-corroles are macrocycle organic molecules with numerous practical applications. In particular, copper corroles exhibit an interesting saddled geometry, which has attracted significant attention from theoreticians and experimentalists over the years. The present work is dedicated to understand the effect of structural saddling in a copper corrole on potential probe signals via imaging ultrafast coherent electron dynamics. A linearly polarized pulse is used to trigger the electron dynamics and time-resolved x-ray diffraction is employed to image the triggered dynamics. It is found that the symmetry reduction in the time-resolved diffraction signals and electronic flux densities is a signature of the saddling in a copper corrole during ultrafast charge migration. Moreover, analysis of the electronic flux density reveals that the diagonal nitrogen atoms mediate coherent charge migration between them via a central copper atom. Correlation of the flux densities and the diffraction signals indicates that the signature of the charge migration is encoded in time-resolved diffraction signals. A comparison of the static diffraction signals of nonsaddled planar copper porphyrin and saddled nonplanar copper corrole in their ground states is made.

physics.chem-ph↗

arXiv2021

Imaging charge-migration in chiral molecules using time-resolved x-ray diffraction

Four-dimensional imaging of charge migration is crucial to the understanding of several ubiquitous processes in nature. The present work focuses on imaging of charge migration in an oriented epoxypropane: a chiral molecule. A linearly polarized pulse is used to induce the charge migration, which is imaged by time-resolved x-ray diffraction. It is found that the total time-resolved diffraction signals are significantly different for both enantiomers. Furthermore, a connection between time-resolved x-ray diffraction and the electronic continuity equation is discussed by analyzing the time-dependent diffraction signal and the time derivative of the total electron density in the momentum space.

physics.chem-ph↗

arXiv2020

Signatures of the orbital angular momentum of an infrared light beam in the two-photon transition matrix element: A step toward attosecond chronoscopy of photoionization

We present a theory of time-resolved photoionisation in the presence of a vortex beam. In a pump-probe setup, an extreme ultraviolet or an x-ray pump pulse triggers ionization, which is probed by a synchronized infrared pulse with non-zero orbital angular momentum. We show, how this property of the probe pulse affects the electron dynamics upon ionization, in a way that is independent of the initial and final angular momentum states of the ionizing system.

physics.atom-ph↗

arXiv2019

Probing molecular chirality via laser-induced electronic fluxes

Chirality is ubiquitous in nature and of fundamental importance in science. The present work focuses on understanding the conditions required to modify the chirality during ultrafast electronic motion by bringing enantiomers out-of-equilibrium. Different kinds of ultrashort linearly-polarised laser pulses are used to drive an ultrafast charge migration process by the excitation of a small number of low-lying excited states from the ground electronic state of S- and R-epoxypropane. Control over chiral electron dynamics is achieved by choosing the different orientations of the linearly polarised pulse. We find that chirality breaking electric fields are only possible in oriented molecules, and that charge migration remains chiral when the polarisation of the field lies in the mirror plane defining the enantiomer pair, or when it is strictly perpendicular to it. Ultimately, the presence or the absence of a mirror symmetry for the enantiomer pair in the external field determines the chiral properties of the charge migration process.

physics.chem-ph↗