Category Archives: 2007

Metanematic transitions in a bilayer system: Application to the bilayer ruthenate

It was suggested that the two consecutive metamagnetic transitions and the large residual resistivity discovered in Sr3Ru2O7 can be understood via the nematic order and its domains in a single layer system. However, a recently reported anisotropy between two longitudinal resistivities induced by tilting the magnetic field away from the c axis cannot be explained within the single layer nematic picture. To fill the gap in our understanding within the nematic order scenario, we investigate the effects of bilayer coupling and in-plane magnetic field on the electronic nematic phases in a bilayer system. We propose that the in-plane magnetic field in the bilayer system modifies the energetics of domain formation, since it breaks the degeneracy of two different nematic orientations. Thus, the system reveals a pure nematic phase with a resistivity anisotropy in the presence of an in-plane magnetic field. In addition to the nematic phase, the bilayer coupling opens a different route to a hidden nematic phase that preserves the x-y symmetry of the Fermi surfaces.

Christoph Puetter, Hyeonjin Doh*, and Hae-Young Keeā€ 
Department of Physics, University of Toronto, Toronto, Ontario, Canada M5S 1A7

Classical Antiferromagnet on a Hyperkagome Lattice

Motivated by recent experiments on Na4Ir3O8 [Y. Okamoto, M. Nohara, H. Aruga-Katori, and H. Takagi, arXiv:0705.2821 (unpublished)], we study the classical antiferromagnet on a frustrated three-dimensional lattice obtained by selectively removing one of four sites in each tetrahedron of the pyrochlore lattice. This “hyperkagome” lattice consists of corner-sharing triangles. We present the results of large-N mean field theory and Monte Carlo computations on ON classical spin models. It is found that the classical ground states are highly degenerate. Nonetheless a nematic order emerges at low temperatures in the Heisenberg model (N = 3) via “order by disorder,” representing the dominance of coplanar spin configurations. Implications for ongoing experiments are discussed.

John M. Hopkinson,1 Sergei V. Isakov,1 Hae-Young Kee,1 and Yong Baek Kim1,2
1Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada
2Department of Physics, University of California, Berkeley, California 94720, USA