Thermodynamics of the $d$=3+1 Quantum XY Model

TL;DR

This paper systematically analyzes the thermodynamics of the 3+1 dimensional quantum XY model at low temperatures, including higher-order corrections and the influence of spin-wave interactions, extending previous one-loop results.

Contribution

It provides a three-loop order analysis of the thermodynamics of the 3+1 quantum XY model, including corrections to free energy and magnetic properties, which were previously limited to one-loop order.

Findings

Free energy density receives $T^6$ and $T^8$ corrections to the $T^4$ Bose gas term.

Spin-wave interactions significantly influence magnetization and susceptibility.

Comparison with 2+1 dimensional case highlights dimensional effects.

Abstract

Within effective field theory we explore the properties of the $d$=3+1 quantum XY model at low temperatures and in weak magnetic or staggered fields. For this parameter regime only few results appear to be known, and furthermore are restricted to one-loop order. In the present study we systematically analyze the thermodynamics of the $d$=3+1 quantum XY model up to three-loop order. In the low-temperature expansion of the free energy density, the free Bose gas term of order $T^4$ receives corrections of order $T^6$ and $T^8$. The discussion also includes the pressure, (staggered) magnetization and susceptibility. In particular, we show how these quantities are influenced by the spin-wave interaction. We then compare our findings with those for the quantum XY model in $d$=2+1.