arXiv subjects

Udai Prakash Tyagi

Publications and source records attributed to Udai Prakash Tyagi.

11 recordsLinked to original sources

arXiv2025

An investigation of the two-dimensional non-Hermitian Su-Schrieffer-Heeger Model

This communication presents an examination of a two-dimensional, non-Hermitian Su -Schrieffer-Heeger (SSH) model, which is differentiated from its conventional Hermitian counterpart by incorporating gain and/or loss terms, mathematically represented by imaginary on-site potentials. The time-reversal symmetry is disrupted due to these on-site potentials. Exceptional points in a non-Hermitian system feature eigenvalue coalescence and non-trivial eigenvector degeneracies. Utilization of the rank-nullity theorem and graphical analysis of the phase rigidity factor enable identification of true exceptional points. Furthermore, this investigation achieves vectorized Zak phase quantization and examines a topolectric RLC circuit to derive the corresponding topological boundary resonance condition and the quantum Hall susceptance. Although Chern number quantization is not feasible, staggered hopping amplitudes corresponding to unit-cell lattice sites lead to broken inversion symmetry with non-zero Berry curvature, resulting in finite anomalous Nernst conductivity.

cond-mat.mes-hall↗

arXiv2025

Two-dimensional non-Hermitian Su-Schrieffer-Heeger Model

A particle-hole symmetry protected 2D non-Hermitian Su-Schrieffer-Heeger (SSH) model is investigated. This version differs from the usual Hermitian version by the inclusion of gain and/or loss terms which are represented by complex on-site potentials. The exceptional points occur, when the dimensionless potential magnitude and the hopping amplitudes become close to unity, leading to the coalescence of eigenvalues and nontrivial eigenvector degeneracies. Furthermore, the vectored Zak phase quantization has been obtained and a topolectric RLC circuit has been analysed. If realized experimentally (in photonic and acoustic crystals), the quantization is expected to lead to an extended bulk-boundary correspondence.

quant-ph↗

arXiv2024

Anomalous Nernst Effect in Ferromagnetic Weyl Semimetal

In a three-dimensional Dirac semimetal the time reversal symmetry (TRS) or the inversion symmetry (IS) is not broken. With either of these symmetries broken, the Dirac points in the three-dimensional band structure split up into pairs of so-called Weyl points. The ferromagnetic Weyl semimetals (FMWSM), such as Co3Sn2S2, feature pairs of Weyl points characterized by the opposite chiralities. In this communication we study FMWSM based on TRS broken continuum and lattice Hamiltonians. The latter one is more realistic and represents Co3Sn2S2. These models include all essential ingredients leading to the formation of a pair of Weyl nodes and tilted Weyl cones. Our analysis shows a large anomalous Nernst conductivity which is unlocked due to the divergent Berry curvature - a local manifestation of the geometric properties of electronic wavefunctions - at Weyl points.

cond-mat.mes-hall↗

arXiv2024

Quantum anomalous Hall effect induced by circularly polarized light on samarium hexaboride surface

We examine a time-dependent, surface Hamiltonian for the 3D compound samarium hexaboride based on the slave boson protocol linked version of the periodic Anderson model reported earlier. The problem of large on-site electron-electron repulsion was reformulated in terms of a holonomic constraint involving a term representing the spatially-independent Slave boson-condensate. In this communication, we show the possible access to the quantum anomalous Hall state due to the normal incidence of circularly polarized light on the surface of the compound in the high frequency limit within the framework of the Floquet theory. The value of the term is mildly affected by the intensity of incident radiation. The chern number is found to be unity for the right-handed as well as the left-handed circularly polarized light.

cond-mat.mes-hall↗

arXiv2024

Theoretical Investigation of the Periodic Anderson Hamiltonian of Samarium Hexaboride

The periodic Anderson Hamiltonian of the bulk samarium hexaboride is investigated in this article assuming the presence of ferromagnetic impurities (FM). The problem of large on-site electron-electron repulsion is reformulated in terms of a holonomic constraint using slave-boson technique. The model analysis yields the effective mass of electron and the possibility of the quantum anomalous Hall phase with integer value of the Chern number. Upon using the Fu-Kane-Mele formalism, it is indicated that the surface Hamiltonian without FM may correspond to a strong topological insulator.

cond-mat.mes-hall↗

arXiv2023

On Weyl Nodes in Ferromagnetic Weyl Semimetal

The ferromagnetic Weyl semimetals, such as Co3Sn2S2, feature pairs of Weyl points characterized by the opposite chiralities.We model this type of semimetals by the inversion symmetry protected and the time reversal symmetry broken Bloch Hamiltonian. It involves terms representing the tunnelling effect, exchange field corresponding to the ferromagnetic order, chirality index of Weyl points with related energy parameters, and the angle formed by the spin magnetic moments and the axis perpendicular to the system-plane. While for the in-plane spin moment order the Weyl nodes are absent at some points of the first Brillouin zone , the bands of opposite chirality non-linearly cross each other with band inversion at Weyl points for the spin moment order along the perpendicular axis. The absence of linearity implies that the system is unable to host massless Weyl fermions. We also show that, in the absence of the exchange field, the incidence of the circularly polarized radiation leads to the emergence of a novel state with broken time reversal symmetry.

cond-mat.mes-hall↗

arXiv2023

Tunable Radiation Field Aided Quantum Spin Hall Phase in Bi2Se3Thin Film

We show fledgling quantum spin Hall phase by the normal incidence of near-infrared circularly polarized radiation field on Bismuth Selenide doped with magnetic impurities. For this purpose, we start with a low-energy two-dimensional, time-dependent Hamiltonian. The time dependence in the Hamiltonian arises due to the optical field describable by the associated gauge field. We make use of the Floquet theory in the high-frequency limit to investigate the system. The optical field tuneability leads to the emergence of the spin Hall phase, when intensity of the incident radiation is high, from the quantum anomalous Hall phase. Interestingly, the former phase is achievable here even in the presence of the magnetic impurities.

cond-mat.mes-hall↗

arXiv2023

Some information on acoustic topological insulator

In this exceedingly short review article, we have provided some information on acoustic topological insulator for pedagogical purpose. Since, intrinsically acoustic systems do not have Kramers doublets due to spin-zero status, artificially acoustic spin-half states could be engineered as reported in refs. 5-26 maintaining time reversal symmetry. The high point of this article is an explanation of emergent Dirac physics in acoustic topological insulators.

cond-mat.mes-hall↗

arXiv2022

Fledgling quantum spin Hall effect in pseudo gap phase of Bi2212

We study the emergence of the quantum spin Hall (QSH) states for the pseudo-gap (PG) phase of Bi2212 bilayer system, assumed to be D-density wave(DDW) ordered, starting with a strong Rashba spin-orbit coupling(SOC) armed, and the time reversal symmetry (TRS) complaint Bloch Hamiltonian. The presence of strong SOC gives rise to non-trivial, spin-momentum locked spin texture tunable by electric field. The emergence of quantum anomalous Hall effect with TRS broken Chiral DDW Hamiltonian of Das Sarma et al. is found to be possible.

cond-mat.mes-hall↗

arXiv2022

Electron spin orientation dependence on momentum in pseudo gap phase of Bi2212

The aim of the paper is to study the electron spin direction dependence on momentum due to the presence of Rashba spin-orbit coupling in the pseudo-gap phase of Bi2212 bilayer. The non-trivial spin texture in k-space is found tuneable by electric field. The dependence is reported earlier by a group of workers in a spin- and angle-resolved photoemission spectroscopic measurement. The synthetic spin-orbit coupling, characterized by the broken time-reversal symmetry, is expected to be useful for the manipulation of the spin orientation.

cond-mat.supr-con↗

arXiv2021

Chiral d density wave ordered pseudo gap phase of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ bilayer. Spin texture and Dzyaloshinskii Moriya interaction

We model Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ (Bi2212) bilayer system by an inversion symmetry broken and time reversal non invariant Bloch Hamiltonian H. The pseudo-gap phase of the bilayer is assumed to be chiral d density wave ordered. The focal point of the paper is the theoretical study of the spin momentum locking (SML), due to the presence of a strong spin orbit coupling in Bi2212, reported earlier in this phase in a spin and angle resolved photoemission spectroscopic measurement. The non trivial spin texture in k space is found tunable by electric field and also by intercalation.The Dzyaloshinskii Moriya interaction (DMI) coefficient, where DMI being important energy for chiral textures like magnetic skyrmions, are calculated to set the stage for detailed studies in a sequel. We also find that,in the nodal region, in the presence of Zeeman field B , as in a s wave superconductor, for B greater than or equal to B_c (a critical value) a vortex in this system becomes a non-Abelian anyon with a Majorana zero mode required for the fault tolerant quantum computation.

cond-mat.supr-con↗