Impact of ordering competition on the global phase diagram of iron pnictides

TL;DR

This paper uses renormalization group analysis to study how competition among superconductivity, spin density wave, and nematic order reshapes the phase diagram of iron pnictides, revealing suppressed superconductivity and reentrant nematic order.

Contribution

It provides a detailed RG-based theoretical framework showing how ordering competition alters phase transitions and the phase diagram in iron pnictides.

Findings

Superconductivity can be strongly suppressed by competing orders.

Nematic order exists only in an intermediate temperature range.

The phase diagram exhibits a reentrant nematic phase due to thermal fluctuations and competition.

Abstract

We consider the impact of the competition among superconductivity, spin density wave, and nematic order in iron pnictides, and show that the ordering competition substantially reshapes the global phase diagram. We perform a detailed renormalization group analysis of an effective field theory of iron pnictides and derive the flow equations of all the physical parameters. Using these results, we find that superconductivity can be strongly suppressed by the ordering competition, and also extract the $T$-dependence of superfluid density. Moreover, the phase transitions may become first order. Interestingly, our RG analysis reveal that the nematic order exists only in an intermediate temperature region $T_{m}< T < T_{n}$, but is destroyed at $T > T_{n}$ by thermal fluctuation and at $T < T_{m}$ by ordering competition. This anomalous existence of nematic order leads to a back-bending of the nematic transition line on the phase diagram, consistent with the observed reentrance of tetragonal structure at low temperatures. A modified phase diagram is obtained based on the RG results.