arXiv subjects

Samir Kumar Pal

Publications and source records attributed to Samir Kumar Pal.

6 recordsLinked to original sources

arXiv2023

Magnetism in AV3Sb5 (A = Cs, Rb, K): Complex Landscape of the Dynamical Magnetic Textures

We have investigated the dynamical magnetic properties of the V-based kagome stibnite compounds by combining the ab-initio calculated magnetic parameters of a spin Hamiltonian like inter-site exchange parameters, magnetocrystalline anisotropy and site projected magnetic moments, with full-fledged simulations of atomistic spin-dynamics. Our calculations reveal that in addition to a ferromagnetic order along the [001] direction, the system hosts a complex landscape of magnetic configurations comprised of commensurate and incommensurate spin-spirals along the [010] direction. The presence of such chiral magnetic textures may be the key to solve the mystery about the origin of the experimentally observed inherent breaking of the C6 rotational symmetry- and the time-reversal symmetry.

cond-mat.mtrl-sci↗

arXiv2023

Magnetism in AV3Sb5 (Cs, Rb, K): Origin and Consequences for the Strongly Correlated Phases

The V-based kagome systems AV3Sb5 (A = Cs, Rb and K) are unique by virtue of the intricate interplay of non-trivial electronic structure, topology and intriguing fermiology, rendering them to be a playground of many mutually dependent exotic phases like charge-order and superconductivity. Despite numerous recent studies, the interconnection of magnetism and other complex collective phenomena in these systems has yet not arrived at any conclusion. Using first-principles tools, we demonstrate that their electronic structures, complex fermiologies and phonon dispersions are strongly influenced by the interplay of dynamic electron correlations, non-trivial spin-polarization and spin-orbit coupling. An investigation of the first-principles-derived inter-site magnetic exchanges with the complementary analysis of q-dependence of the electronic response functions and the electron-phonon coupling indicate that the system conforms as a frustrated spin-cluster, where the occurrence of the charge-order phase is intimately related to the mechanism of electron-phonon coupling, rather than the Fermi-surface nesting.

cond-mat.str-el↗

arXiv2021

Combinatorial Large-area MoS2/Anatase-TiO2 interface: A Pathway to Emergent Optical and Opto-electronic Functionalities

Interface of transition metal dichalcogenide (TMDC) and high-k dielectric transition metal oxides (TMO) had triggerred umpteen discourses due to the indubitable impact of TMO in reducing the contact resistances and restraining the Fermi-level pinning for the metal-TMDC contacts. In the present work, we focus on the unresolved tumults of large-area TMDC/TMO interfaces, grown by adopting different techniques. Here, on a pulsed laser deposited (PLD) MoS2 thin film, a layer of TiO2 is grown by using both atomic layer deposition (ALD) and PLD. These two different techniques emanate TiO2 layers with different crystalline properties, thicknesses and interfacial morphologies, subsequently influencing the electronic and optical properties of the interfaces. In addition, they manifest a boost in the extent of p-type doping with increasing thickness of TiO2, as emerged after analyzing the core-level shifts of the X-ray photoelectron spectra (XPS). Density functional analysis of the MoS2/Anatase-TiO2 interfaces, for pristine and in presence of a wide range of interfacial defects, could explain the interdependence of doping and the terminating atomic-surface of TiO2 on MoS2. The optical properties of the interface, encompassing the photoluminescence, transient absorption and z-scan two-photon absorption indicate the presence of defect-induced localized mid-gap levels in MoS2/TiO2 (PLD), resulting quenched exciton signals. On the contrary, the relatively defect-free interface in MoS2/TiO2 (ALD) demonstrates a clear presence of both A and B excitons of MoS2. From the investigation of optical properties, we indicate that MoS2/TiO2 (PLD) interface may act as a promising saturable absorber. Moreover, MoS2/TiO2 (PLD) interface had resulted a better photo-transport. A potential application of MoS2/TiO2 (PLD) is demonstrated by the fabrication of a p-type photo-transistor with the ionic-gel top gate.

cond-mat.mtrl-sci↗

arXiv2020

Intriguing electronic and optical prospects of FCC bimetallic two-dimensional heterostructures: epsilon near-zero behaviour in UV-vis range

Higher superconducting critical temperature and large-area epsilon-near-zero interfaces are two long-standing goals of Condensed Matter Physics and Optics. Motivated by the recent advancements of experimental interests on metallic nanostructures, we have theoretically investigated some selected bimetallic FCC combinations starting from large-area interface to embedded and doped two-dimensional (2D) nanostructures. Using different first-principles techniques, encompassing density functional theory (DFT), time-dependent DFT (TDDFT), phonon and DFT-coupled quantum transport, we propose the prospects of some selective bimetallic nanostructures like Au/Ag and Pt/Pd to exhibit exotic electronic phenomena. For 2D doped and embedded nanostructures of these systems, non-trivial band-structure and Fermi-surface topology may be emblematic to the presence of instabilities like charge density waves. We specifically highlight the optical attributes extracted from the TDDFT calculations for these systems, where interfacial morphology induced band-localization leads to near-zero behavior of both real and imaginary parts of the dynamical dielectric response is observed in the ultra-violet to visible (UV-vis) optical range. Low-energy intra-band plasmonic oscillations present for individual metallic surfaces are completely suppressed for embedded and doped nanostructures. Phonon-dispersion of the model systems indicates the presence of soft phonons and dynamical instabilities. Quantum transport calculations on simplest possible device made out of these bimetallic systems reveals generation of highly transmitting pockets over the cross-sectional area for some selected device geometry. We envisage that, if observed experimentally, such systems may lead to many fascinating physics and applications in many diverse fields ranging from condensed matter physics to optics or even more.

cond-mat.supr-con↗

arXiv2020

Broken Inversion Symmetry and Interface-induced Spin-polarization for metal-Weyl semimetal stacked interfaces

Weyl semimetal TaAs, a congenial host to the massless Weyl fermions, spontaneously lacks the time-reversal and the inversion symmetry and thus effectuates topologically stable Weyl nodes, resembling magnetic monopoles in momentum space. Former experimental analysis had revealed that the near-zero spin-polarization of bulk TaAs experiences a boost in presence of point-contacts of non-magnetic metals along with the associated phenomena of tip-induced superconductivity, providing the impetus to study the large-area stacked interfaces of TaAs with Noble metals like Au and Ag. First-principles calculations on these interfacial systems have manifested an increment of the interface-induced spin-polarization and contact-induced transport spin-polarization. In contrast to the single interface, for stacked system, the broken inversion symmetry of the system introduces a z-directional band-dispersion resulting in an energetically separated series of Weyl cones. The Weyl cones for TaAs/Ag and TaAs/Au stacked interfaces are observed to be of type-I and type-II nature respectively. Thus, the current study demonstrates the designing of two different types of spin-polarized Weyl systems from non-magnetic metal and type I Weyl components.

cond-mat.mes-hall↗

arXiv2018

Intricate modulation of interlayer coupling at GO/MoSe2 interface: application in time-dependent optics and device transport

In GO/MoSe2 semiconductor heterostructure, we have demonstrated a subtle control on the doping dynamics by modulating interlayer coupling through the combination of strain-reducing relative rotation of the constituting layers and variation of ligand type and concentration. By first-principles calculations incorporating spin-orbital coupling, we have investigated the impact of variable interlayer coupling in introducing non-collinear magnetic behaviour in the heterostructure. The outcome of varying carrier type and their respective concentrations are investigated by static as well as time dependent density functional calculations, which indicates presence of optical anisotropy and time-dependent optical phenomena like exciton quenching and band-gap renormalization. Performance of such heterostructures as channel material in devices with top and edge metal contacts is analyzed. Our self-consistent quantum transport calculations have evinced that the nature of interface-induced variation in doping is extrapolated for devices only in the case of top contacts. The edge contact, although exhibits a better transmission, are inefficient for sensing the ligand-induced doping modulation introduced via vertical inter-layer charge transfer.

cond-mat.mtrl-sci↗