In systems with strong electron-lattice coupling, such as manganites, orbital degeneracy is lifted, causing a null expectation value of the orbital magnetic moment. magnetic structure is thus determined by spin-spin superexchange. In titanates, however, with much smaller Jahn-Teller distortions, orbital degeneracy might allow non-zero values of the orbital magnetic moment, and novel forms of ferromagnetic superexchange interaction unique to t 2g electron systems have been theoretically predicted, although their experimental observation has remained elusive. In this paper, we report a new kind of Ti 3 + ferromagnetism at Lamno 3 /srTio 3 epitaxial interfaces. It results from charge transfer to the empty conduction band of the titanate and has spin and orbital contributions evidencing the role of orbital degeneracy. The possibility of tuning magnetic alignment (ferromagnetic or antiferromagnetic) of Ti and mn moments by structural parameters is demonstrated. This result will provide important clues for understanding the effects of orbital degeneracy in superexchange coupling.

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We propose a new technique for the detection of single atoms in ultracold quantum gases. The technique is based on scanning electron microscopy and employs the electron impact ionization of trapped atoms with a focused electron probe. Subsequent detection of the resulting ions allows for the reconstruction of the atom's position. This technique is expected to achieve a much better spatial resolution compared to any optical detection method. In combination with the sensitivity to single atoms, it makes new in situ measurements of atomic correlations possible. The detection principle is also well suited for the addressing of individual sites in optical lattices.

We report high-resolution, bulk Compton scattering measurements unveiling the Fermi surface of an optimally doped iron-arsenide superconductor, Ba͑Fe 0.93 Co 0.07 ͒ 2 As 2 . Our measurements are in agreement with first-principles calculations of the electronic structure, revealing both the X-centered electron pockets and the ⌫-centered hole pockets. Moreover, our data are consistent with the strong three dimensionality of one of these sheets that has been predicted by electronic structure calculations at the local-density-approximation-minimum As position. Complementary calculations of the noninteracting susceptibility, 0 ͑q , ͒, suggest that the broad peak that develops due to interband Fermi-surface nesting, and which has motivated several theories of superconductivity in this class of material, survives the measured three dimensionality of the Fermi surface in this family.The discovery of superconductivity in LaO 1−x F x FeAs, a member of the so-called "1111" family of iron-pnictide materials, 1 has triggered intense research into its nature and origin. Tempted by the proximity of the superconductivity in these compounds to an antiferromagnetic spin-density-wave ͑SDW͒ state, many theoretical models have focused on spin fluctuations as the key, 2,3 supported by first-principles calculations of the electronic structure. Such calculations predict four Fermi-surface ͑FS͒ sheets: two hole sheets at the center of the Brillouin zone ͑BZ͒ and two electron sheets centered at its corner. 4,5 In the undoped ͑and lightly doped͒ "1111" compounds the hole and electron sheets are well nested, leading to a broad peak in the noninteracting susceptibility. 2 The spin fluctuations that are thought to develop from this FS instability have already been observed in neutronscattering measurements, 6 and theoretical models suggest that they promote a strong pairing interaction, provided that the order parameter changes phase between the hole and electron FS sheets ͑the so-called s Ϯ model͒. 2,3 Central to such models, however, is a detailed understanding of the topology of the FS; here we present a bulk measurement of the FS of an optimally doped iron-arsenide superconductor, Ba͑Fe 0.93 Co 0.07 ͒ 2 As 2 , alongside complementary calculations of the noninteracting susceptibility, 0 ͑q , ͒. We demonstrate the data are most consistent with a three-dimensional ͑3D͒ FS but that the nesting that is required for the s Ϯ model survives, lending its availability to all iron-pnictide compounds.Ba͑Fe 1−x Co x ͒ 2 As 2 is a member of the "122" family of iron-pnictide superconductors, with a maximum T c ϳ 24 K for x ϳ 0.06. 7,8 Unlike the "1111" family, whose FS is quasitwo-dimensional ͑2D͒, the "122" compounds are predicted by electronic structure calculations to have substantial 3D warping of one of the hole sheets, 5 the degree of which is sensitive to the position of the As with respect to the Fe plane. Experimental studies have not yet adequately resolved whether the electronic structure is better described by the experimental As position or...

We report on the production of a F = 1 spinor condensate of 87 Rb atoms in a single beam optical dipole trap formed by a focused CO 2 laser. The condensate is produced 13 mm below the tip of a scanning electron microscope employing standard all-optical techniques. The condensate fraction contains up to 100,000 atoms and we achieve a duty cycle of less than 10 s.