Charge and spin collective modes in a quasi-1D model of Sr2RuO4

TL;DR

This paper investigates collective charge and spin modes in a quasi-1D model of Sr2RuO4, showing how their energies depend on the orbital contributions to superconductivity, which can be experimentally distinguished.

Contribution

It provides a theoretical analysis of collective modes in Sr2RuO4, linking their energies to the orbital origin of superconductivity, offering a method to identify dominant bands.

Findings

Collective mode energies are small compared to the pairing gap if superconductivity is mainly from quasi-1D bands.

Mode energies become comparable to the pairing gap with significant involvement of the quasi-2D band.

Measuring these modes can reveal the orbital nature of the superconducting state.

Abstract

Given that Sr2RuO4 is a two-component p-wave superconductor, there exists the possibility of well defined collective modes corresponding to fluctuations of the relative phase and spin-orientation of the two components of the order parameter. We demonstrate that at temperatures much below Tc, these modes have energies small compared to the pairing gap scale if the superconductivity arises primarily from the quasi 1D (dxz and dyz) bands, while it is known that their energies become comparable to the pairing gap scale if there is a substantial involvement of the quasi 2D (dxy) band. Therefore, the orbital origin of the superconductivity can be determined by measuring the energies of these collective modes.