Bulletin of the American Physical Society
2005 72nd Annual Meeting of the Southeastern Section of the APS
Thursday–Saturday, November 10–12, 2005; Gainesville, FL
Session NA: Condensed Matter Invited Session |
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Chair: Carlos Sa de Melo, Georgia Tech University Room: Hilton Century A |
Saturday, November 12, 2005 10:45AM - 11:21AM |
NA.00001: Transforming organic superconductors, magnets, and insulators with high magnetic fields Invited Speaker: Accessible high magnetic fields are ideally matched with the energy scales of electronic and magnetic structure in organic charge transfer complexes. In this presentation some of the more dramatic (and also sometimes controversial) examples of how various ground states are probed, are changed, or are induced in high magnetic fields will be discussed. Avenues to push high field probes of the unusual ground states of these material well beyond conventional transport and magnetization methods will also be discussed. [Preview Abstract] |
Saturday, November 12, 2005 11:21AM - 11:57AM |
NA.00002: Orbital Physics: Colossal Magnetoresistance and Quantum Oscillations in the Mott System Ca$_{3}$Ru$_{2}$O$_{7}$ Invited Speaker: Ca$_{3}$Ru$_{2}$O$_{7}$ features a Mott transition, colossal magnetoresistance and quantum oscillations. Ca$_{3}$Ru$_{2}$O$_{7 }$shows strikingly different behavior when the field is applied along the different crystal axes. A ferromagnetic (FM) state with full spin polarization is achieved for B$\vert \vert a-$axis, but colossal magnetoresistance is realized \textit{only} for B$\vert \vert b$-axis by avoiding the ferromagnetic state. For B$\vert \vert c$-axis, Shubnikov-de Haas oscillations are observed and followed by a less resistive state than for B$\vert \vert a$. Hence, in contrast to standard colossal magnetoresistive materials, the FM phase is the least \textit{favorable} for electron hopping. In addition, for B rotating within the \textit{ac}-plane, slow and strong Shubnikov-de Haas (SdH) oscillations periodic in 1/B are observed for T$\le $1.5 K in the presence of metamagnetism. These oscillations are highly angular dependent and intimately correlated with the spin-polarization of the ferromagnetic state. For B$\vert \vert $[110], oscillations are also observed \textit{but periodic in B }(rather than 1/B)\textit{ which persist up to 15 K. } While the SdH oscillations are a manifestation of the presence of small Fermi surface (FS) pockets in the Mott-like system, the B-periodic oscillations, an exotic quantum phenomenon, may be a result of anomalous coupling of the magnetic field to the $t_{2g}$-orbitals that makes the extremal cross-section of the FS field-dependent. [Preview Abstract] |
Saturday, November 12, 2005 11:57AM - 12:33PM |
NA.00003: Non-uniform Triplet Superconductivity in Low-Dimensional Conductors. Invited Speaker: The interplay between magnetic and superconducting orders is a very important problem in condensed matter physics. In the quasi-one-dimensional (quasi-1D) organic conductor (TMTSF)$_2$PF$_6$, an antiferromagnetic state charaterized by a spin density wave (SDW) neighbors a triplet superconducting (TSC) state in the P-T phase diagram. Experiments [1,2] suggest a coexistence region of SDW and TSC orders in the vicinity of the phase boundary. We consider a tight-binding quasi-1D electron system, and derive the Ginzburg-Landau (GL) free energy for simultaneous SDW and TSC orders. By solving the linearized GL equations in the limit where the coupling between SDW and TSC order parameters is small, a non-uniform TSC state appears with simultaneous non-uniform SDW order. \\ References:\\ $[1]$ T. Vuletic {\it et al.}, Eur. Phys. J. B {\bf 25}, 319 (2002).\\ $[2]$ I. J. Lee {\it et al.}, Phys. Rev. Lett. {\bf 94}, 197001 (2005). [Preview Abstract] |
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