arXiv subjects
Publications and source records attributed to Nepal Banerjee.
Here we have simulated effect of quenched type random-bond disorder during the XY transition.Here we have studied the spontaneous magnetization(M),heat-capacity(Cv) with T.Here we notice a spontaneous symmetry breaking and observe quasi long range order (QLRO) at ground state in presence of this type of bond-random disorder.
Here we have simulated the random-bond type quenched disorder in 3D Heisenberg magnet.Here we have used classical Monte-Carlo simulation with Heisenberg spin and use 3D simple cubic lattice for this simulation.Here we use Metropolis single spin flipping algorithm.
The recent breakthrough discovery of twisted bilayer $CrI_3$ system, where both ferromagnetic and antiferromagnetic order coexist and act as a main motivation for simulating simple magnetic systems where this type of mixed-phase arises. Here we have simulated the dilute magnetic alloy with generic type $A_pB_{1-p}$. Here A and B are ferromagnetic and antiferromagnetic type magnetic atoms. Here we have studied the mixed phase and tetra-critical behavior of that dilute magnet. We have simulated the critical behavior of that kind of mixed-phase at different doping strengths. Here we have observed a mixed phase rather than a spin-glass(SG) phase in this site random(SR) disorder model. Here we have used classical Monte-Carlo simulation with Heisenberg spin and used a 3D simple cubic lattice for this simulation.
Spontaneous symmetry breaking of 2D isotropic Heisenberg magnet is restricted by Mermin-Wagner theorem at any finite temperature in presence of short-range exchange interaction.Kosterlitz and Thouless using XY spin model showed that how an order state could developed in 2D spin system in presence of short range isotropic interaction.Very recent discovery of several van der waals magnet revised and redefined our understanding on 2D Heisenberg magnet and its ground state properties.After a rigorous and careful study of several 2D magnetic material we have realized from both experimentally and numerically that the finite size of a 2D system has great impact on the ground state symmetry breaking.Because of that finite size effect more often an anisotropic residual magnetic moment is generated and trigger the spontaneous symmetry breaking at finite temperature(T) and even only presence of short-range interaction we observed the phase transition of that Heisenberg spin system.In this present work we have shown the basic role of finite size,anisotropy during the symmetry breaking of 2D Heisenberg XY magnet.Here we have simulated Kosterlitz-Thouless transition using classical Monte-carlo simulation and study the effect of anisotropy during the phase transition.We presented the behaviour of different thermodynamic properties of 2D XY spin model system during the Kosterlitz-Thouless(KT) transition.The generic characteristic of KT transition which make it distinct from other critical phenomena is that the peak of heat capacity is not diverging with increase of system size rather peak is decreasing with the increasing of system size near at transition temperature.Here we are observing that behaviour in our present simulation and that specific behaviour help us for classifying the present transition as Kosterlitz-Thouless(KT) transition.
Recent discovery of several van der waals magnetic material and moire magnet introduce to us an extremely challenging and revolutionary era of 2D magnetism and correlated phenomena for low dimensional material.More often the simplest spin models which is based on inter-atomic exchange and spin-orbit coupling(SOC) potentially able to capture and explain the critical phenomena of extremely complicated correlated magnetic material.In this work we have attempted to simulate 3D Heisenberg magnet using classical Monte Carlo simulation.Our goal is to establish a new and simplest spin simulation technique which can help us to understand those van der waals magnet from its microscopic length scale.Here we have been proposing a completely new methodology of classical Monte Carlo simulation of Heisenberg spin which is based on single spin flipping Metropolis algorithm.Our state of art simulation technique potentially able to study the phase transition of isotropic XY(O(2)) and XYZ(O(3))spin model very efficiently.With this simulation technique we overcome the barrier of critical slowing down during the phase transition in a effective way and able to predict the transition temperature($T_c$) very accurately.
We predict that antiferromagnetic bilayers formed from van der Waals (vdW) materials, like bilayer CrI$_3$, have a strong magnetoelectric response that can be detected by measuring the gate voltage dependence of Faraday or Kerr rotation signals, total magnetization, or anomalous Hall conductivity. Strong effects are possible in single-gate geometries, and in dual-gate geometries that allow internal electric fields and total carrier densities to be varied independently. We comment on the reliability of density-functional-theory estimates of interlayer magnetic interactions in van der Waals bilayers, and on the sensitivity of magnetic interactions to pressure that alters the spatial separation between layers.
Symmetry plays an important role in the topological band theory to remedy the eigenstates' gauge obstruction at the cost of a symmetry anomaly and zero-energy boundary modes. One can also make use of the symmetry to enumerate the topological invariants - giving a symmetry classification table. Here we consider various topological phases protected by different symmetries, and examine how the corresponding topological invariants evolve once the protecting symmetry is spontaneously lost. To our surprise, we find that the topological invariants and edge states can sometimes be robust to symmetry breaking quantum orders. This topological robustness persists as long as the mean-field Hamiltonian in a symmetry breaking ordered phase maintains its adiabatic continuity to the non-interacting Hamiltonian. For example, for a time-reversal symmetric topological phase in 2+1D, we show that the Z_2 time-reversal polarization continues to be a good topological invariant even after including distinct time-reversal breaking order parameters. Similar conclusions are drawn for various other symmetry breaking cases. Finally, we discuss that the change in the internal symmetry associated with the spontaneous symmetry breaking has to be accounted for to reinstate the topological invariants into the expected classification table.