Condensed Matter Physics Seminar

2 p.m., Thursday, April 19, 2001
Room 1201, Physics Building

 Electronic Structure and Properties of the Heavy Electron Oxides LiV2O4 and NaCo2O4

David J. Singh

(Center for Computational Materials Science, Naval Research Laboratory, Washington, DC)

Abstract:  Spinel structure LiV2O4 was discovered to be a heavy fermion compound, while NaCo2O4 is a paramagnetic metal with an unusually high thermopower and specific heat.  In this talk, density functional studies of these materials are presented.  NaCo2O4, the high value of U/W notwithstanding, has transport properties in very close agreement with those calculated with an unrenormalized band structure.  LiV2O4 is found to be a metal with local moment magnetic character and antiferromagnetic  interactions.  The moments are formed from the ag component of the V t2g manifold.  The remainder of the V t2g orbitals participate in itinerant lighter mass bands.  This has superficial similarities to f-band heavy fermions, but closer examination reveals that a direct mapping is not possible due to off-diagonal effects, particularly Hund's coupling and Coulomb correlation, arising because the local moments and conduction bands are derived from the same atomic d shell.  This opens the door to other explanations of the heavy fermion behavior related to geometrical frustration and non-collinear spin arrangements.

Host:  Amitava Chattopadhyay

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