arXiv subjects

Sudipta Dutta

Publications and source records attributed to Sudipta Dutta.

At least 19 recordsLinked to original sources

arXiv2026

Spin-1 Dirac dispersion and Chern insulating phases in 2D honeycomb Sierpi\'nski fractal

Graphene-based Sierpi\'nski fractals host a zero-energy chiral mode and spin-1 Dirac dispersions within the nearest-neighbor tight-binding model. However, the presence of complex next-nearest neighbor hopping arising from the local flux and the staggered Semenoff mass terms, modeled within the Haldane Hamiltonian, breaks the time-reversal and spatial inversion symmetries, respectively, and makes these flat bands dispersive. Moreover, they introduce rich topological phases in this class of systems that can be characterized by Chern numbers up to $\pm 3$, i.e., beyond the conventional honeycomb lattice. These observations pave the way for the exploration of 2D periodic fractals beyond graphene, where topological phase transitions can be realized through externally applied fields.

cond-mat.mes-hall↗

arXiv2026

Massive fields in 3D Minkowski space and boundary correlators

A codimension-one Carrollian CFT on null infinity has been proposed as the putative dual description of asymptotically flat spacetimes and has so far been successful in describing the massless S-matrices in one higher dimension. In this work, we investigate the current proposal of Carrollian holography to include the massive fields in the bulk. We discover a broader class of correlation functions in two-dimensional Carrollian CFTs and show that they encode massive scattering amplitudes in three-dimensional Minkowski spacetime. We also construct a bulk-to-boundary propagator that generalizes the one already existing for massless fields.

hep-th↗

arXiv2026

Breaking Bipartite and Time Reversal Symmetries by Fusing Porphine Unit in-between two Zigzag-edge Graphene Nanoribbons

Hybrid structure of two zigzag-edge graphene nanoribbons with a fused porphine ring in between, results in two distinct nearly degenerate ground states: a semiconducting antiferromagnetic state and a conducting ferromagnetic state with unequal and opposite Fermi velocities of majority and minority spins, the former having slightly higher stability. Such ground states result from the broken bipartite symmetry induced by the porphine ring. The incorporation of different transition metal atoms in the porphine cavity reduces their energy difference but keeps their electronic properties mostly unchanged. The splitting of the $d$-orbitals in the distorted square-planar ligand field of porphine produces a high spin ground state that breaks the global time reversal symmetry ($\mathcal{T}$). The opposite Fermi velocities of the majority and minority spins in the ferromagnetic ground state and lower sensitivity of the conducting majority spin channel to the edge disorder, make this class of quasi-one-dimensional hybrid structures promising for dual spin-filtering device applications.

cond-mat.mtrl-sci↗

arXiv2025

Anisotropic conformal Carroll field theories and their gravity duals

We investigate anisotropic conformal Carroll field theories and their holographic duals. On the field theory side, we focus on the case with scaling exponent $z=0$ in two and three spacetime dimensions. These theories exhibit infinite-dimensional symmetry algebras, including supertranslations and superrotations, and are closely related to, but distinct from, Warped Conformal Field Theories. We construct the associated Carrollian stress tensor, derive its transformation properties, and analyse the structure of correlation functions under different choices of vacua. On the gravity side, we identify three and four-dimensional plane wave geometries whose isometry algebras realise the two- and three-dimensional Carroll algebra and anisotropic scale transformations. We propose, for each scaling exponent, a phase space of asymptotically-plane wave spacetimes and show that the residual diffeomorphisms reproduce the expected conformal Carroll field theory algebra, establishing a framework for anisotropic Carrollian holography.

hep-th↗

arXiv2025

Multi Moire Networks in Engineered Lateral Hetero-Bilayers: Programmable Phononic Reconfiguration and Second Harmonic Generation

Moire engineering in two-dimensional transition metal dichalcogenides enables access to correlated quantum phenomena. Realizing such effects demands simultaneous control over twist angle and material composition to modulate phonons, excitons, and their interactions. However, most studies rely on exfoliated flakes, limiting scalability and systematic exploration. Here, we demonstrate a scalable multi-moire network by vertically stacking CVD-grown monolayer lateral heterostructures. Signatures of moire non-rigidity, including phonon frequency softening, linewidth broadening, and strain localization, are attributed to two lattice relaxation modes; rotational reconstruction and volumetric dilation. Micro-angle-resolved photoemission spectroscopy reveals that interfacial orbital interactions modulate interlayer coupling. At aligned angles, molybdenum diselenides exhibit reduced valley polarization and Davydov splitting, indicating strain-induced symmetry breaking and chiral phonon effects. Notably, SHG modulation was obderved with variation in twist angle due to lower coherence and band-offset-driven phase delay. First-principles calculations support these findings. This work provides a route to programmable, scalable multi-moire platforms for opto-straintronics, quantum sensing, and on-chip photonics.

cond-mat.mes-hall↗

arXiv2024

Quantum Transport through Asymmetrical Molecular channel Azulene: Role of Orbital Interference

We investigate electron transport through azulene molecule with four distinct electrode contact geometries using the non-equilibrium Green's function formalism within the tight-binding Hamiltonian. Employing the Q-matrix approach, we analyze quantum interference (QI) among the molecular orbitals in each contact configuration. Our results reveal distinct transmission profiles and varying current responses among configurations, with the configuration 1-3 displaying the highest conductivity at higher bias due to strong constructive interference of the Highest Occupied Molecular Orbital (HOMO). Conversely, configuration 5-7 exhibit weak conductance and antiresonance at the Fermi energy, attributed to dominant destructive interference among the frontier molecular orbitals. Configuration 2-6 is found to exhibit asymmetric I-V characteristics, due to the dipolar nature of the azulene molecule. These findings underscore the significance of QI effects in shaping the transport properties of azulene, and molecule-based devices in general.

cond-mat.mes-hall↗

arXiv2024

Quantum Interference Driven Electron Transport through Fano-Anderson Systems

We investigate the electronic transport behavior of Fano-Anderson (FA) systems, consisting of a one-dimensional finite backbone chain and an attached side-group of varying length. The tight-binding model within the non-equilibrium Green's function (NEGF) reveals distinct interference patterns between the frontier orbitals of odd and even side-group systems that lead to distinct transport mechanisms across various configurations. The even side-group systems exhibit resonant tunneling peaks, while the odd ones demonstrate significant destructive interference at Fermi energy leading to antiresonance and reduced current responses. Further exploration of the role of electron-electron interactions within mean-field Hubbard Hamiltonian indicates the emergence of negative differential resistance (NDR) in odd side-group systems at lower biases, a phenomenon absent in the non-interacting case. Our study demonstrates the critical role of quantum interferences among the frontier molecular orbitals and electron correlations in shaping the transport behavior of FA systems, providing insights for the design of molecular-scale electronic devices.

cond-mat.mes-hall↗

arXiv2024

Identifying the phases of Kane-Mele Hubbard Hamiltonian in momentum space: A many-body configuration interaction study

We investigate the magnetic and conduction properties of Kane-Mele Hubbard model in quasi one-dimensional honeycomb ribbon systems at half-filling by varying the strength of both spin-orbit interaction and on-site Coulomb correlation term. We use the numerical many-body configuration interaction (CI) method to investigate the dispersions of charge and spin gaps along with the momentum resolved spin-density profile over the full Brillouin zone. While the spin sector retains its topological nature at all values of spin-orbit coupling and Hubbard term, we report a new signature of the topological phase transition in the charge sector. This phase transition from a topological band insulating phase to a antiferromagnetically ordered Mott insulating phase is characterized by a shift of the many-body charge gap minima from Brillouin zone boundary to Dirac point. Our results provide a better understanding of the shifting of the gap-closing point in the momentum space which was reported in an earlier mean-field study of the same model and suggests an alternative numerical route to detect topological phase transition in strongly-correlated systems in terms of their momentum space behaviors.

cond-mat.str-el↗

arXiv2024

3D Stress Tensor for Gravity in 4D Flat Spacetime

Three dimensional (3d) Carrollian CFTs are potential co-dimension one holographic duals of 4d asymptotically flat spacetimes that live on the whole of the null boundary. In this paper, we show that the local stress tensor of the 3d Carrollian conformal theory (without any additional sources) constructed in terms of the geometric structure at asymptotic null infinity naturally encodes both the leading and subleading soft graviton theorems. We relate the 3d Carroll stress tensor to the 2d Celestial one and show how the 3d version naturally localises the non-local 2d Celestial stress tensor. We also comment on the relation with stress tensors in relativistic 3d CFTs and connections to the flat limit of AdS/CFT.

hep-th↗

arXiv2024

Stress tensors of 3d Carroll CFTs

We discuss kinematical features of conformal Carroll field theories in three dimensions (3d). Conformal extension of Carroll algebra is infinite dimensional even in 3d unlike its relativistic counterpart, and hence 3d Carroll CFTs share similarities with 2d CFT. We provide a construction for the conserved charges for Carrollian CFTs and an expression for stress tensor OPEs consistent with the algebra of charges. We discuss a free field model where these symmetries are realised and explicitly compute the OPEs verifying our construction. In addition we comment on the possibility of extending the conformal symmetries to diffeomorphisms of spatial slice for these Carrollian theories.

hep-th↗

arXiv2024

Excitonic circular dichroism in boron-nitrogen clusters decorated graphene

Within the first principle calculations, we propose a boron and nitrogen cluster incorporated graphene system for efficient valley polarization. The broken spatial inversion symmetry results in high Berry curvature at K and K' valleys of the hexagonal Brillouin zone in this semiconducting system. The consideration of excitonic quasiparticles within GW approximation along with their scattering processes within many-body Bethe-Salpeter equation gives rise to an optical gap of 1.72 eV with an excitonic binding energy of 0.65 eV. Owing to the negligible intervalley scattering, the electrons in opposite valleys are selectively excited by left- and right-handed circular polarized lights, as evident from the oscillator strength calculations. Therefore, this system can exhibit circular-dichroism valley Hall effect in the presence of the in-plane electric field. Moreover, such excitonic qubits can be exploited for information processing.

cond-mat.mtrl-sci↗

arXiv2024

Superconductivity in Ca-intercalated bilayer silicene

Within first-principles calculations, we explore superconductivity in Ca-intercalated bilayer silicene compound, Si2CaSi2. This arises from the coupling of interlayer flower-like Γ-centered Fermi surface formed by the hybridization of Ca-3d and Si-3pz orbitals with low-energy out-of-plane vibrations enabled by silicene's buckling. The consequent large electron-phonon coupling, as evident from the Eliashberg spectral function leads to superconductivity below 5.4 K in this two-dimensional covalent system. Our results reveal the key control parameters to achieve superconductivity in experimentally synthesizable silicon-based thin materials that can find diverse applications.

cond-mat.supr-con↗

arXiv2024

Holography in Flat Spacetimes: the case for Carroll

We compare and contrast the two approaches of holography in asymptotically flat spacetimes, viz. the co-dimension two Celestial approach based on the Mellin transformation and the co-dimension one Carrollian approach based on the modified Mellin and elucidate how some of the problems of the Celestial approach can be rectified by the Carrollian one. Considering flat holography as a limit from AdS/CFT makes a co-dimension one dual more plausible, and our previous construction of Carrollian correlations from AdS Witten diagrams is testimony to this. In this paper, we show how to generalize our earlier analysis for operators with spin. We work out a large number of explicit non-trivial examples (twelve) and show matching between the limit of AdS$_4$ Witten diagrams and 3d boundary symmetry considerations, thus making the case for the Carrollian dual even stronger.

hep-th↗

arXiv2023

A Centralized Voltage Controller for Offshore Wind Plants: NY State Grid Case Study

This paper proposes a centralized multi-plant reactive power and voltage controller to support voltage control in the interconnected onshore power system. This controller utilizes a hierarchical control structure consisting of a master controller and multiple slave controllers. To validate the proposed method, a realistic planning case of the New York State grid is created for the year 2035, in which nearly 9,500 MW AC or DC connected offshore wind resources are modeled. The performance of the proposed controller is analyzed in the large-scale model under three realistic disturbance scenarios: generator loss, load ramps, and load steps. Results demonstrate how the controller can adequately perform under disturbances to share reactive support proportionally among plants based on their ratings and improve grid voltage stability margins.

eess.SY↗

arXiv2023

Circular dichroism in two-dimensional BC$_6$N and B$_3$C$_2$N$_3$ in absence of intervalley excitonic coupling

Two-dimensional (2D) noncentrosymmetric systems offer potential opportunities for exploiting the valley degrees of freedom for advanced information processing, owing to non-zero Berry curvature. However, such valley polarization in 2D materials is crucially governed by the intervalley excitonic scattering in momentum space due to reduced electronic degrees of freedom and consequent enhanced electronic correlation. Here, we study the valley excitonic properties of two 2D noncentrosymmetric complementary structures, namely, BC$_6$N and B$_3$C$_2$N$_3$ using first principles-based GW calculations combined with the Bethe-Salpeter equation (BSE), that brings the many-body interactions among the quasiparticles. The \textbf{k}-resolved oscillator strength of their first bright exciton indicates their ability to exhibit valley polarization under the irradiation of circularly polarized light of different chiralities. Both the systems show significant singlet excitonic binding energies of 0.74 eV and 1.31 eV, respectively. Higher stability of dark triplet excitons as compared to the singlet one can lead to higher quantum efficiency in both the systems. The combination of large excitonic binding energies and the valley polarization ability with minimal intervalley scattering make them promising candidates for applications in advanced optical devices and information storage technologies.

cond-mat.mtrl-sci↗

arXiv2023

Valley-polarization and stable triplet exciton formation in 2D lateral heterostrcuture of hBN-kagome and graphene

Broken spatial inversion symmetry in semiconducting materials with time-reversal pair valleys can exhibit valley polarization. Based on first-principles calculations, here we propose a lateral heterostructure of kagome lattice of hBN and hexagonal graphene domains that exhibits opposite Berry curvature in inequivalent K and K' valleys. Explicit consideration of excitonic scattering processes within GW and Bethe-Salpeter equation formalism confirm insignificant intervalley coupling and consequent valley polarization ability along with 0.46 eV higher binding energy of triplet excitons. Such heterostructure with large charge carrier mobility can be exploited for advanced valleytronic and optoelectronic applications.

cond-mat.mtrl-sci↗

arXiv2023

Asymmetric Electronic Transport in Porphine: Role of Atomically Precise Tip-Electrode

Electronic conductance through a single molecule is sensitive towards its structural orientation between two electrodes, owing to the distribution of molecular orbitals and their coupling to the electrode levels, that are governed by quantum confinement effects. Here, we vary the contact geometry of the porphine molecule by attaching two Au tip electrodes that resemble the mechanical break junction, via thiol anchoring groups. We investigate the current-voltage characteristics of all the contact geometries using non-equilibrium Green's function formalism along with density functional theory and tight-binding framework. We observe varying current responses with changing contact sites, originating from varied wave-function delocalization and quantum interference effect. Our calculations show asymmetric current-voltage characteristics under forward and reverse biases due to structural asymmetry of the tip electrodes in either sides of the molecule. We establish this phenomenon as a universal feature for any molecular electronic device, irrespective of the inherent structural symmetry of a molecule. This will provide fundamental insights of electronic transport through single molecule in real experimental setup. Furthermore, our observations of varying current response can further motivate the fabrication of sensor devices with porphine based biomolecules that control important physiological activities, in view of their applications in advanced diagnostics.

cond-mat.mes-hall↗

arXiv2023

AdS Witten Diagrams to Carrollian Correlators

Carrollian Conformal Field Theories (CFTs) have been proposed as co-dimension one holographic duals to asymptotically flat spacetimes as opposed to Celestial CFTs which are co-dimension two. In this paper, drawing inspiration from Celestial holography, we show by a suitable generalisation of the flat space limit of AdS that keeps track of the previously disregarded null direction, one can reproduce Carrollian CFT correlation functions from AdS Witten diagrams. In particular, considering Witten diagrams in AdS4, we reproduce two and three-point correlation functions for three dimensional Carrollian CFTs in the so-called delta-function branch. Along the way, we construct non-trivial Carrollian three-point functions in the delta-branch by considering a collinear limit. We also obtain a generalised anti-podal matching condition that now depends on the retarded time direction.

hep-th↗