SearcharxivSearch

arXiv subjects

Santanu Dhara

Publications and source records attributed to Santanu Dhara.

2 recordsLinked to original sources

Role of Noise on Defect Formation and Correlations in a Long-Range Ising Model Under Adiabatic Driving

We study an exactly solvable long-range (LR) transverse-field Ising model (TFIM) with a power-law decaying interaction characterized by a decay exponent α. In the thermodynamic limit, the system is adiabatically driven in the presence of noise, from a paramagnetic phase with all spins down to one with all spins up. Our study examines the role of long-range interactions on the defect density, its distribution, and spin correlations, comparing noisy and noiseless scenarios. In the noiseless case, within the long-range regime, the steady-state properties are primarily influenced by modes near the k = π region. However, in the presence of noise, the dominant contributions shift to the modes near k = 0. This differs from the SR model, where previous studies have shown that modes around k = π/2 play a significant role under noisy conditions. In the absence of noise, defect density scales as $n\propto τ_Q^{-1/2}$, implying scaling exponent independent of decay exponent. However, we find that decreasing the value of α (i.e., increasing the range) enhances the defect density, whereas in the presence of noise, it is suppressed. In the LR regime, two-point fermionic correlators initially exhibit Gaussian decay, followed by quadratic suppression instead of power-law decay for both noisy and noiseless scenarios. Meanwhile, spin correlators, expressed as a string of fermionic operators, undergo purely exponential decay with no crossover behavior. Furthermore, our analysis of defect formation reveals the influence of LR interaction on the kink-number distribution and its cumulants.

cond-mat.other

Driven one-dimensional noisy Kitaev chain

We study one-dimensional Kitaev chain driven by the anisotropy parameter, $J_{-}= t/τ_Q$, in the presence of weak Gaussian noise in the parameter $J_{+}$. The system is prepared in the ground state of the Hamiltonian at the initial time $t\rightarrow -\infty$. The defect density and the residual energy at the end of the drive protocol reveals anti-Kibble Zurek (AKZ) behavior which deviates from the earlier reported linear in quench time dependence for the defect density. The entropy density at the end of the protocol is found to exhibit the signature of the AKZ behavior. In the context of the Kitaev chain, the two-point spin correlators are short ranged. The hidden topological order across the quantum phase transition point is probed via the non-local string order parameters. The two-point Majorana correlator and the hidden string correlator calculated in the final decohered state at the end of the noisy drive protocol is consistent with the AKZ picture. We have analyzed the kink statistics in the dual spin space, the first three cumulants at the end of the noisy drive also exhibit the AKZ scaling behavior for slower sweeps similar to the defect density. The kink distribution function is well approximated with the normal distribution with non-universal noise dependent mean and variance.

cond-mat.stat-mech