arXiv subjects

M. Suman Kalyan

Publications and source records attributed to M. Suman Kalyan.

3 recordsLinked to original sources

arXiv2023

Tuning electronic properties in transition metal dichalcogenides MX$_2$ (M= Mo/W, X= S/Se) heterobilayers with strain and twist angle

We explore the direct to indirect band gap transitions in MX$_2$ (M= Mo/W, X= S/Se) transition metal dichalcogenides heterobilayers for different system compositions, strains, and twist angles based on first principles density functional theory calculations within the G$_0$W$_0$ approximation. The obtained band gaps that typically range between 1.4$-$2.0 eV are direct/indirect for different/same chalcogen atom systems and can often be induced through expansive/compressive biaxial strains of a few percent. A direct to indirect gap transition is verified for heterobilayers upon application of a finite 16$^{\circ}$ twist that weakens interlayer coupling. The large inter-layer exciton binding energies of the order of $\sim$~250~meV estimated by solving the Bethe-Salpeter equation suggest these systems are amenable to be studied through infrared and Raman spectroscopy.

cond-mat.mtrl-sci↗

arXiv2023

Stochastic resonance in a model of a periodically driven DNA : Multiple transitions, scaling and sequence dependence

We numerically study stochastic resonance in the unzipping of a model double-stranded DNA by a periodic force. We observe multiple peaks in stochastic resonance in the output signal as the driving force frequency is varied for different force amplitudes, temperature, chain length, and chain heterogeneity. Multiple peaks point to the existence of multiple stable and metastable states, which correspond to dynamical states of partially zipped and unzipped conformations and transitions between them. We quantify such transitions by looking at the time evolution of the fraction of bound base pairs. We obtain phase diagrams in the force amplitude-temperature plane both in the resonance frequency of the primary peak and the output signal at the peak value. We further obtain an excellent scaling behavior of the output signal for changing lengths of the DNA. Resonance behavior is also affected by chain heterogeneity as it depends strongly on which base pair the periodic forcing is applied.

cond-mat.soft↗

arXiv2019

Unzipping DNA by a periodic force: Hysteresis loops, Dynamical order parameter, Correlations and Equilibrium curves

The unzipping of a double stranded DNA whose ends are subjected to a time dependent periodic force with frequency $ω$ and amplitude $G$ is studied using Monte Carlo simulations. We obtain the dynamical order parameter, $Q$, defined as the time average extension between the end monomers of two strands of the DNA over a period, and its probability distributions $P(Q)$ at various force amplitudes and frequencies. We also study the time autocorrelations of extension and the dynamical order parameter for various chain lengths. The equilibrium force-distance isotherms were also obtained at various frequencies by using non-equilibrium work measurements.

cond-mat.soft↗