arXiv subjects

Sunny Gupta

Publications and source records attributed to Sunny Gupta.

23 records · Page 2Linked to original sources

arXiv2020

Heterobilayers of 2D materials as a platform for excitonic superfluidity

Excitonic condensate has been long-sought within bulk indirect-gap semiconductors, quantum wells, and 2D material layers, all tried as carrying media. Here we propose intrinsically stable 2D semiconductor heterostructures with doubly-indirect overlapping bands as optimal platforms for excitonic condensation. After screening hundreds of 2D materials, we identify candidates where spontaneous excitonic condensation mediated by purely electronic interaction should occur, and hetero-pairs Sb2Te2Se/BiTeCl, Hf2N2I2/Zr2N2Cl2, and LiAlTe2/BiTeI emerge promising. Unlike monolayers, where excitonic condensation is hampered by Peierls instability, or other bilayers, where doping by applied voltage is required, rendering them essentially non-equilibrium systems, the chemically-specific heterostructures predicted here are lattice-matched, show no detrimental electronic instability, and display broken type-III gap, thus offering optimal carrier density without any gate voltages, in true-equilibrium. Predicted materials can be used to access different parts of electron-hole phase diagram, including BEC-BCS crossover, enabling tantalizing applications in superfluid transport, Josephson-like tunneling, and dissipationless charge counterflow.

cond-mat.mes-hall↗

arXiv2018

In Pursuit of 2D Materials for Maximum Optical Response

Despite being only a few atoms thick, single-layer two-dimensional (2D) materials display strong electron-photon interactions that could be utilized in efficient light modulators on extreme subwavelength scales. In various applications involving light modulation and manipulation, materials with strong optical response at different wavelengths are required. Using qualitative analytical modeling and first-principles calculations, we determine the theoretical limit of the maximum optical response such as absorbance (A) and reflectance (R) in 2D materials and also conduct a computational survey to seek out those with best A and R in various frequency ranges, from mid-infrared (IR) to deep ultraviolet (UV). We find that 2D boron has broadband reflectance R >99% for >100 layers, surpassing conventional thin films of bulk metals such as silver. Moreover, we identify 2D monolayer semiconductors with maximum response, for which we obtain quantitative estimates by calculating quasiparticle energies and accounting for excitonic effects by solving the Bethe-Salpeter equation (BSE). We found several monolayer semiconductors with absorbances >30% in different optical ranges which are more than half of the maximum possible value for a 2D material. Our study predicts 2D materials which can potentially be used in ultra-thin reflectors and absorbers for optoelectronic application in various frequency ranges.

cond-mat.mes-hall↗

arXiv2017

Topologically nontrivial electronic states in CaSn$_{3}$

Based on the first-principles calculations, we theoretically propose topologically non-trivial states in a recently experimentally discovered superconducting material CaSn$_3$. When the spin-orbit coupling (SOC) is ignored, the material is a host to three-dimensional topological nodal-line semimetal states. Drumhead like surface states protected by the coexistence of time-reversal and mirror symmetry emerge within the two-dimensional regions of the surface Brillouin zone connecting the nodal lines. When SOC is included, unexpectedly, each nodal line evolves into two Weyl nodes (W1, W2) in this centrosymmetric material. Berry curvature calculations show that these nodes occur in a pair and act as either a source or sink of Berry flux. The material also has unique surface states in the form of Fermi arcs, which unlike other known Weyl semimetal, form closed loops of surface states on the Fermi surface. Our theoretical realization of topologically non-trivial states in a superconducting material paves the way towards unraveling the interconnection between topological physics and superconductivity.

cond-mat.mtrl-sci↗

arXiv2014

Big Data: Overview

Big data is data that exceeds the processing capacity of traditional databases. The data is too big to be processed by a single machine. New and innovative methods are required to process and store such large volumes of data. This paper provides an overview on big data, its importance in our live and some technologies to handle big data.

cs.OH↗

arXiv2014

Importance and Techniques of Information Hiding : A Review

Information or data is very crucial resource to us. Thus securing the information becomes all the more necessary. The communication media through which we send data does not provide data security, so other methods of securing data are required. Information hiding plays a very crucial role today. It provided methods for encrypting the information so that it becomes unreadable for any unintended user. This paper reviews the techniques that exist for data hiding and how can these be combined to provide another level of security.

cs.CR↗