Superfluid dome in the spatially modulated two-dimensional XY model

TL;DR

This paper investigates how spatial modulation in a 2D XY model affects the critical temperature, revealing a dome-shaped dependence due to vortex pinning, which enhances understanding of intertwined superconducting and charge-ordered phases.

Contribution

It introduces a novel study of a modulated 2D XY model, demonstrating a non-monotonic $T_c$ dependence and linking vortex pinning to the modulation effects.

Findings

$T_c$ exhibits a dome-like dependence on modulation wavelength.

Peak $T_c$ shifts to longer wavelengths with increased modulation strength.

Vortex pinning explains the non-monotonic $T_c$ behavior.

Abstract

In strongly correlated electron systems, superconductivity and charge density waves often coexist in close proximity, suggesting a deeper relationship between these competing phases. Recent research indicates that these orders can intertwine, with the superconducting order parameter coupling to modulations in the electronic density. To elucidate this interplay, we study a two-dimensional XY model with a periodic modulation of the coupling strength in one spatial direction. Using a combination of tensor network methods and Monte Carlo simulations, we reveal a non-monotonic, dome-like dependence of $T_c$ on the modulation wavelength, with the peak $T_c$ shifting to longer wavelengths as the modulation strength grows. The origin of this phenomenon is traced back to an effective pinning of vortices in the valleys of the modulation, confirmed by a comparison to modulated $q$-state clock models. These findings shed new light on the phase behavior of intertwined superconducting and charge-ordered states, offering a deeper understanding of their complex interactions.