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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