Josephson array of mesoscopic objects. Modulation of system properties through the chemical potential

TL;DR

This paper investigates how changing the chemical potential affects the phase states of a 2D Josephson array of mesoscopic objects, revealing oscillations between superconducting and normal states driven by quantum fluctuations.

Contribution

It provides a detailed phase diagram of the system using a lattice boson Hubbard model and quantum Monte Carlo, highlighting the impact of chemical potential modulation on system states.

Findings

Oscillations between superconducting and normal states with chemical potential changes.

Dependence of system properties on occupation number varies across phase diagram regions.

Reduced fluctuation region width at lower temperatures and stronger interactions.

Abstract

The phase diagram of a two-dimensional Josephson array of mesoscopic objects is examined. Quantum fluctuations in both the modulus and phase of the superconducting order parameter are taken into account within a lattice boson Hubbard model. Modulating the average occupation number $n_0$ of the sites in the system leads to changes in the state of the array, and the character of these changes depends significantly on the region of the phase diagram being examined. In the region where there are large quantum fluctuations in the phase of the superconducting order parameter, variation of the chemical potential causes oscillations with alternating superconducting (superfluid) and normal states of the array. On the other hand, in the region where the bosons interact weakly, the properties of the system depend monotonically on $n_0$. Lowering the temperature and increasing the particle interaction force lead to a reduction in the width of the region of variation in $n_0$ within which the system properties depend weakly on the average occupation number. The phase diagram of the array is obtained by mapping this quantum system onto a classical two-dimensional XY model with a renormalized Josephson coupling constant and is consistent with our quantum Path-Integral Monte Carlo calculations.