Tuesday, April 24, 2012

1204.5032 (Hyun-Jung Lee et al.)

Low-energy spin excitation around coexistent phase of antiferromagnetism
and d-wave superconductivity
   [PDF]

Hyun-Jung Lee, Tetsuya Takimoto
A heavy fermion compound CeRhIn$_5$ is suggested to be in a coexistent phase with commensurate antiferromagnetism and d-wave superconductivity in a pressure region by the nuclear quadrupole resonance (NQR) measurement. In order to clarify the low-energy spin excitation in the coexistent phase, we have applied the RPA method to an itinerant model, where the one-particle state is characterised by two mean-field terms of commensurate antiferromagnetism and d-wave supercon- ductivity, in addition to a kinetic term. In the phase diagram with a parameter set, the coexistent phase appears between the d-wave superconducting phase and the antiferromagnetic phase. Around the transition line between the antiferromagnetic and the coexistent states, an incommensurate spin fluctuation developes additionally because of a nesting between Fermi surfaces in the magnetic Brillouin zone. This feature reminds of the switching of magnetic ordering wave vector observed in the neutron diffraction. The stabilization of the coexistent phase with the commensurate ordering is discussed using the $\pi$-triplet pairing appearing only in the coexistent state. Further, the calcu- lated spin relaxation rate gives a reasonable explanation of the temperature dependence of NQR relaxation rate in the system with the coexistent ground state.
View original: http://arxiv.org/abs/1204.5032

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