Low-energy Spin Excitation in Coexistent Phase of Antiferromagnetism and d-wave Superconductivity

TL;DR

This study investigates low-energy spin excitations in a heavy fermion compound with coexisting antiferromagnetism and d-wave superconductivity, revealing incommensurate excitations linked to Fermi surface nesting.

Contribution

The paper applies the RPA method to an itinerant model to analyze spin excitations in a coexistent phase, highlighting the development of incommensurate excitations near phase transitions.

Findings

Incommensurate spin excitations develop near the transition line.

Fermi surface nesting influences low-energy spin dynamics.

Calculated spin relaxation rates match experimental temperature dependence.

Abstract

Nuclear quadrupole resonance measurements have shown evidences that the heavy fermion compound CeRhIn$_5$ exhibits a coexistent phase with commensurate antiferromagnetism and d-wave superconductivity. In order to clarify the nature of the spin-excitations in the coexistent phase, we have applied the RPA method to an itinerant model, where the effective interaction is given by two mean-field terms of commensurate antiferromagnetism and d-wave superconductivity. It is shown that, around the transition line between the antiferromagnetic and the coexistent states, a low-energy incommensurate spin-excitation is found to develop due to Fermi surface nesting. This feature reminds of the switching of magnetic ordering wave vector observed in the neutron diffraction. Further, we also calculate spin relaxation rate, which gives a reasonable explanation of the temperature dependence of NQR relaxation rate in the system with the coexistent ground state.