Effects of the vortices and impurities on the nuclear spin relaxation rate in iron-based superconductors

TL;DR

This paper investigates how vortices and impurities influence the spin-lattice relaxation rate in iron-based superconductors with different pairing symmetries, revealing similar responses in s±- and d-wave states under certain conditions.

Contribution

It provides a comparative analysis of vortex and impurity effects on quasiparticle excitations and relaxation rates across multiple pairing symmetries in iron-based superconductors.

Findings

Vortices enhance quasiparticle excitations and relaxation rates for all symmetries.

Relaxation rate follows a T^3 dependence, becoming nearly linear at low temperatures.

Impurities amplify effects in s±- and d-wave symmetries, making them hard to distinguish experimentally.

Abstract

The effects of magnetic vortices and nonmagnetic impurities on the low energy quasiparticle excitations and the spin-lattice relaxation rate are examined in the iron-based superconductors for the $s_{\pm}$-, $s$- and d-wave pairing symmetries, respectively. The main effect of the vortices is to enhance the quasiparticle excitations and the spin-lattice relaxation rate for all symmetries, and leads to a $T^{3}$ dependence of the relaxation rate followed by a nearly $T$-linearity at lower temperatures. This enhancement can only be seen for the $s_{\pm}$- and d-wave symmetries in the presence of nonmagnetic impurities. These results suggest that the $s_{\pm}$-wave and d-wave pairing states behave similarly in response to the magnetic field and nonmagnetic impurities, therefore it may be impossible to distinguish them on the basis of the measurements of spin-lattice relaxation rates when a magnetic field and/or impurity scatterings are present.