Quantum critical singularities in two-dimensional metallic XY ferromagnets

TL;DR

This paper develops a scaling function for quantum-critical fluctuations in 2D metallic XY ferromagnets, matching experimental data without adjustable parameters and applicable to various quantum-critical systems.

Contribution

It constructs a universal scaling function for the 2D ferromagnetic quantum-critical point, linking theoretical models with experimental observations in metallic compounds.

Findings

The scaling function accurately describes the frequency, temperature, and magnetic field dependence of correlations.

The theory matches experimental data from YFe₂Al₁₀ without adjustable exponents.

The model applies to superconductor-insulator transitions and metallic antiferromagnetic QCPs.

Abstract

An important problem in contemporary physics concerns quantum-critical fluctuations in metals. A scaling function for the momentum, frequency, temperature and magnetic field dependence of the correlation function near a 2D-ferromagnetic quantum-critical point (QCP) is constructed, and its singularities are determined by comparing to the recent calculations of the correlation functions of the dissipative quantum XY model (DQXY). The calculations are motivated by the measured properties of the metallic compound YFe$_2$Al$_{10}$, which is a realization of the DQXY model in 2D. The frequency, temperature and magnetic field dependence of the scaling function as well as the singularities measured in the experiments are given by the theory without adjustable exponents. The same model is applicable to the superconductor-insulator transitions, classes of metallic AFM-QCPs, and as fluctuations of the loop-current ordered state in hole-doped cuprates. The results presented here lend credence to the solution found for the 2D-DQXY model, and its applications in understanding quantum-critical properties of diverse systems.