TY - JOUR

T1 - Unconventional magnetism in imbalanced Fermi systems with magnetic dipolar interactions

AU - Fregoso, Benjamin M.

AU - Fradkin, Eduardo

N1 - Copyright:
Copyright 2010 Elsevier B.V., All rights reserved.

PY - 2010/6/25

Y1 - 2010/6/25

N2 - We study the magnetic structure of the ground state of an itinerant Fermi system of spin-1/2 particles with magnetic dipole-dipole interactions. We show that, quite generally, the spin state of particles depend on its momentum, i.e., spin and orbital degrees of freedom are entangled and taken separately are not "good" quantum numbers. Specifically, we consider a uniform system with nonzero magnetization at zero temperature. Assuming the magnetization is along z axis, the quantum spin states are k -dependent linear combinations of eigenstates of the σz Pauli matrix. This leads to spin structures in momentum space and to the fact that the Fermi surfaces for "up" and "down" spins are not well defined. The system still has a cylindrical axis of symmetry along the magnetization axis. We also show that the self-energy has a universal structure which we determine based on the symmetries of the dipolar interaction and we explicitly calculated it in the Hartree-Fock approximation. We show that the bare magnetic moment of particles is renormalized due to particle-particle interactions and we give order of magnitude estimates of this renormalization effect. We estimate that the above mentioned dipolar effects are small but we discuss possible scenarios where this physics may be realized in future experiments.

AB - We study the magnetic structure of the ground state of an itinerant Fermi system of spin-1/2 particles with magnetic dipole-dipole interactions. We show that, quite generally, the spin state of particles depend on its momentum, i.e., spin and orbital degrees of freedom are entangled and taken separately are not "good" quantum numbers. Specifically, we consider a uniform system with nonzero magnetization at zero temperature. Assuming the magnetization is along z axis, the quantum spin states are k -dependent linear combinations of eigenstates of the σz Pauli matrix. This leads to spin structures in momentum space and to the fact that the Fermi surfaces for "up" and "down" spins are not well defined. The system still has a cylindrical axis of symmetry along the magnetization axis. We also show that the self-energy has a universal structure which we determine based on the symmetries of the dipolar interaction and we explicitly calculated it in the Hartree-Fock approximation. We show that the bare magnetic moment of particles is renormalized due to particle-particle interactions and we give order of magnitude estimates of this renormalization effect. We estimate that the above mentioned dipolar effects are small but we discuss possible scenarios where this physics may be realized in future experiments.

UR - http://www.scopus.com/inward/record.url?scp=77955878816&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77955878816&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.81.214443

DO - 10.1103/PhysRevB.81.214443

M3 - Article

AN - SCOPUS:77955878816

SN - 1098-0121

VL - 81

JO - Physical Review B - Condensed Matter and Materials Physics

JF - Physical Review B - Condensed Matter and Materials Physics

IS - 21

M1 - 214443

ER -