Variational Monte Carlo approach to the two-dimensional Kondo lattice model

TL;DR

This study uses variational Monte Carlo methods to explore the phase diagram of the two-dimensional Kondo lattice model, revealing potential d-wave superconductivity near magnetic instabilities, which is suppressed when magnetic order is considered.

Contribution

It introduces a comprehensive variational Monte Carlo approach to analyze magnetic and superconducting phases in the 2D Kondo lattice model, highlighting the interplay between magnetism and superconductivity.

Findings

Evidence of d-wave superconductivity in the paramagnetic sector.

Magnetic order suppresses superconductivity in the phase diagram.

Superconductivity appears near magnetic instabilities when magnetism is not allowed.

Abstract

We study the phase diagram of the Kondo-lattice model with nearest-neighbor hopping in the square lattice by means of the variational Monte Carlo technique. Specifically, we analyze a wide class of variational wave functions that allow magnetic and superconducting order parameters, so to assess the possibility that superconductivity might emerge close to the magnetic instability, as often observed in heavy fermion systems. Indeed, we do find evidence of d-wave superconductivity in the paramagnetic sector, i.e., when magnetic order is not allowed in the variational wave function. However, when magnetism is allowed, it completely covers the superconducting region, which thus disappears from the phase diagram.