Arka Bandyopadhyay

Indian Institute of Science | IISC · Department of Solid State and Structural Chemistry Unit

Tetragonal graphene (T-graphene) is a theoretically proposed dy- namically stable, metallic allotrope of graphene. In this theoreti- cal investigation, tight binding (TB) model is used to unravel the metal to semiconductor transition of this 2D sheet under the in- fluence of an external magnetic flux. In addition, the environ- ment under which the...

Present work reports an elegant method to address the emergence of two Dirac cones in a non-hexagonal graphene allotrope S-graphene (SG). We have availed nearest neighbour tight binding (NNTB) model to validate the existence of two Dirac cones reported from density functional theory (DFT) computations. Besides, the real space renormalization group...

Inspired by the success of graphene, various two dimensional (2D) non-hexagonal graphene allotropes having sp 2 bonded tetragonal rings in free standing (FS) (hypothetical) form and on different substrates have been proposed recently. These systems have also been fabricated after modifying the topology of graphene by chemical processes. In this rev...

An unprecedented graphyne allotrope with square symmetry and nodal line semimetallic behaviour has been proposed in the two dimensional realm. The emergence of Dirac loop around the high symmetry points in presence of both the inversion and time reversal symmetries is an predominant feature of the electronic band structure of this system. Besides,...

The anomalous Hall effect in time-reversal symmetry broken systems is underpinned by the concept of Berry curvature in band theory. However, recent experiments reveal that the nonlinear Hall effect can be observed in non-magnetic systems without applying an external magnetic field. The emergence of nonlinear Hall effect under time-reversal symmetri...

Topological semimetals (TSMs) with nodal flexible-surfaces currently garner paramount importance due to their exceptional electronic properties. However, nodal flat-surfaces and nodal spheres have only been observed in a few quantum...

The direct experimental probing and detailed imaging of octahedral tilt, along with the control of magnetic ground state and spin-orbit occupancies in an artificially engineered heterointerface through the manipulation of strain via interface engineering, is the long-standing challenging issue addressed in this study. We introduce a novel methodolo...

The π phase shift of quantum oscillations is generally believed to be a smoking gun evidence for nontrivial Berry phase. However, the spin-zero effect, a sign reversal of quantum oscillations at different magnetic field directions, adds an additional π phase shift. Thus, the nontrivial Berry curvature can be concealed by the spin-zero effect, resul...

Silicene, a silicon counterpart of graphene, hass been predicted to possess massless Dirac fermions. Compared to graphene, the effective spin–orbit interaction is quite significant compared to graphene and as a result, buckling in silicene opens a gap of 1.55 meV at the Dirac point. This band gap can be further tailored by applying in plane stress,...

A series of mononuclear manganese(III) complexes [Mn(X-sal2-323)](ReO4) (X = 5 Cl, 1; X = 5 Br, 2; X = 3,5 Cl, 3; X = 3,5 Br, 4; and X = 5 NO2, 5), containing hexadentate ligands prepared using the condensation of N,N'-bis(3-aminopropyl)ethylenediamine and 5- or 3,5-substituted salicylaldehyde, has been synthesized. Variable temperature single-crys...

The role of acetylenic linkage in determining the exotic band structures of 4,12,2- and 4,12,4- graphynes is reported. The Dirac bands, as confirmed by both density functional theory and tight-binding calculations, are robust and stable over a wide range of hopping parameters between sp − sp -hybridized carbon atoms. The shifting of the crossing po...

The real space decimation method has been successfully applied over the years to understand the critical phenomena as well as the nature of single particle excitations in periodic, quasiperiodic, fractal, and decorated lattices in one dimension and beyond. The power of the method is specially revealed through its application in lattice models, lead...

The interplay of topology and non-Hermiticity has led to diverse, exciting manifestations in a plethora of systems. In this work, we systematically investigate the role of non-Hermiticity in the Chern insulating Haldane model on a dice lattice. Due to the presence of a nondispersive flat band, the dice-Haldane model hosts a topologically rich phase...

The interplay of topology and non-Hermiticity has led to diverse, exciting manifestations in a plethora of systems. In this work, we systematically investigate the role of non-Hermiticity in the Chern insulating Haldane model on a dice lattice. Due to the presence of a non-dispersive flat band, the dice-Haldane model hosts a topologically rich phas...

The anomalous Hall effect in time-reversal symmetry broken systems is underpinned by the concept of Berry curvature in band theory. However, recent experiments reveal that the nonlinear Hall effect can be observed in non-magnetic systems without applying an external magnetic field. The emergence of nonlinear Hall effect under time-reversal symmetri...

This theoretical work has availed the first-principles method to critically explore the characterizing Raman spectra of tetragonal graphyne quantum dots. The Raman spectra of these T-graphyne systems possess the fingerprint of both sp and sp2 bonded atoms. We have explored that sp atoms predominate in determining intense Raman peaks over 2000 cm−1....

In this work, we have introduced defects like bond rotation and the sifting of atoms along the non-bonding direction in graphene to come up with a new dynamically stable crystal with a 5-4-4-5 ring geometry. However, on thermal excitation, the system transforms into a thermodynamically more stable phase with a 5-6-5 ring (PHP) structure belonging t...

Graphene turns out to be the pioneering material for setting up boulevard to a new zoo of recently proposed carbon based novel two dimensional (2D) analogues. It is evident that their electronic, optical and other related properties are utterly different from that of graphene because of the distinct intriguing morphology. For instance, the revoluti...

The non-honeycomb lattice phagraphene is energetically comparable with graphene and has recently been experimentally realized in 1D form. This carbon allotrope exhibits asymmetric Dirac cone feature with tunable Fermi velocity against external strain. This work critically presents an analytical scheme to address the emergence and robustness of Dira...

6,6,12-graphyne is the first non-hexagonal lattice that evinced graphene like Dirac fermions. The oligomers of this fascinating carbon system have recently been synthesized via iterative acetylenic coupling reactions. In this work, we have critically explored the characterizing Raman spectra, electronic and optical properties of these synthesized c...

Correction for ‘Electric field induced band tuning, optical and thermoelectric responses in tetragonal germanene: a theoretical approach’ by Supriya Ghosal et al. , Phys. Chem. Chem. Phys. , 2020, 22 , 19957–19968, DOI: 10.1039/D0CP03892J.

In this article, we have systematically explored the electronic, optical and thermo-electric proper- ties of tetragonal germanene (T-Ge) using first-principles calculations. The ground state geometry of pristine T-Ge is buckled and exhibits nodal line semi-metallic behaviour. In addition, we have proposed a tight binding (TB) model Hamiltonian that...

In this paper, we have critically explored the electronic, magnetic and optical properties of stable non-hexagonal carbon allotrope S-graphene (SG). The band structure of SG sheet exhibits two Dirac cones at distinct k→ points. The ab-initio molecular dynamics study reveals the dynamical stability of the sytem upto 600 K. Besides, the sheet possess...

We have critically examined the key role of acetylenic linkages (–CRC–) in determining the opto-electronic responses of dynamically stable tetragonal (T) ‘-ynes’ with the help of a density functional theory method. The presence of –CRC– between two tetra-rings invariably flips the electronic bands about the Fermi level. The underlying physics has b...

A first principles based density functional theory (DFT) has been employed to identify the signature of Stone–Wales (SW) defects in semiconducting graphene quantum dot (GQD). Results show that the G mode in the Raman spectra of GQD has been red shifted to 1544.21 cm − 1 in the presence of 2.08% SW defect concentration. In addition, the intensity ra...

In this theoretical work, we have explored the utilities of non-toxic boron (B)-nitrogen (N) pair substitution on tetragonal graphene (T-graphene/TG) nanodot in CO gas sensing. Within the realm of first-principles calculations, we have identified the two possible doping sites of B-N pair suitable for CO molecule adsorption. This adsorption process...

The physics of two-dimensional (2D) materials is always intriguing in their own right. For all of these elemental 2D materials, a generic characteristic feature is that all the atoms of the materials are exposed on the surface, and thus tuning the structure and physical properties by surface treatments becomes very easy and straightforward. The dis...

In this first principles investigation, we have analysed the refractive indices, optical absorption and conductivity spectra of tetragonal graphene sheet and its experimentally realized substructure, the narrowest arm chair nanoribbon. It is noteworthy that, the oscillatory behaviours encountered in the optical responses are shifted towards the UV...

The physics of two-dimensional (2D) materials is always intriguing in their own right. For all of these elemental 2D materials, a generic characteristic feature is that all the atoms of the materials are exposed on the surface, and thus tuning the structure and physical properties by surface treatments becomes very easy and straightforward. The dis...

A first principles based density functional theory (DFT) has been employed to doped free standing (FS) germanene mono-layer by arsenic (As) and gallium (Ga). It has been revealed that electronic, magnetic and optical properties can be tailored by either (a) type, (b) concentration and (c) choosing specific sites of substitutional doping elements or...

The magnetic and optical properties of Diamond Shaped Graphene Quantum Dots (DSGQDs) have been investigated by varying their sizes with the help of density functional theory (DFT). The study of density of states (DOS) has revealed that the Fermi energy decreases with increase in sizes (number of carbon atoms). The intermediate structure with 30 car...

Tetragonal graphene (TG) is one of the theoretically proposed dynamically stable graphene allotropes. In this study, the Raman spectra, IR spectra and some electronic properties of pristine and doped (single boron (B) and nitrogen (N)) TG have been investigated by first-principles based density functional theory (DFT) at the B3LYP/6-31G(d) level. F...