Spin-orbit coupling induced magnetism in the $d$-density wave phase of La$_{2-x}$Ba$_x$CuO$_4$ superconductors

TL;DR

This paper investigates how spin-orbit coupling influences the $d$-density wave phase in La$_{2-x}$Ba$_x$CuO$_4$, revealing induced ferromagnetism and field-induced orbital currents, with implications for experimental detection.

Contribution

It demonstrates that spin-orbit coupling induces ferromagnetic moments in the DDW phase and predicts field-induced orbital currents if DDW order is absent at zero field.

Findings

Spin-orbit coupling induces ferromagnetic moments in the DDW phase.

Magnetic field can induce orbital currents in the absence of DDW order.

The effects are specific to the low-temperature orthorhombic phase.

Abstract

We study the effects of spin-orbit coupling in the $d$-density wave (DDW) phase. In the low-temperature orthorhombic phase of La$_{2-x}$Ba$_x$CuO$_4$, we find that spin-orbit coupling induces a ferromagnetic moment in the DDW phase, which is polarized along the [110] direction with a considerable magnitude. This effect does not exist in the superconducting phase. On the other hand, if the $d$-density wave order does not exist at zero field, a magnetic field along the [110] direction always induces such a staggered orbital current. We discuss experimental constraints on the DDW states in light of our theoretical predictions.