Order parameter fluctuation and ordering competition in $\mathrm{Ba_{1-x}K_xFe_2As_2}$

TL;DR

This paper uses renormalization group analysis to explore the competition among different magnetic and superconducting orders in Ba_{1-x}K_xFe_2As_2, revealing insights into its phase diagram and stable magnetic states.

Contribution

It provides a theoretical framework to understand the phase diagram and magnetic order competition in Ba_{1-x}K_xFe_2As_2 using renormalization group analysis.

Findings

Critical line of nematic order has a negative slope in the superconducting dome.

Superconductivity is suppressed near the magnetic quantum critical point.

Charge-spin density wave is the stable C4 magnetic state at low temperatures.

Abstract

The competition among superconductivity, stripe-type magnetic order, and a new type of $C_4$ symmetric magnetic order in $\mathrm{Ba_{1-x}K_xFe_2As_2}$ is theoretically studied, focusing on its impact on the global phase diagram. By carrying out a renormalization group analysis of an effective field theory, we obtain the energy-scale dependent flows of all the model parameters, and then apply the results to understand the observed phase diagram. On the basis of the renormalization group analysis, we show that the critical line of nematic order has a negative slope in the superconducting dome and superconductivity is suppressed near the magnetic quantum critical point, which are both consistent with recent experiments. Moreover, we find that, although the observed $C_4$ symmetric magnetic state could be a charge-spin density wave or a spin-vortex crystal at high temperatures, charge-spin density wave is the only stable $C_4$ magnetic state in the low-temperature regime. Therefore, ordering competition provides a method to distinguish these two candidate $C_4$ magnetic states.