Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session K23: Spin Orbit Physics in Iridates and Other Bulk OxidesFocus Session
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Sponsoring Units: GMAG DMP DCOMP Chair: Jasminka Terzic, Univ of Kentucky Room: LACC 402B |
(Author Not Attending)
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K23.00001: NMR Studies on Single Crystalline Na2IrO3 Ziwen Mei, Rajib Sarkar, Matthew Lawson, Ramon Ruiz, Gilbert Lopez, Hans-Henning Klauss, James Analytis, Nicholas Curro Na2IrO3 is considered as a possible candidate to realize Kitaev spin model on the honeycomb lattice. In our case, results of 23Na nuclear magnetic resonance (NMR) measurements are presented. We have studied temperature dependence and crystallographic orientation angular dependence of the NMR shift, and the NMR spin-lattice relaxation rate 1/T1. |
Wednesday, March 7, 2018 8:12AM - 8:24AM |
K23.00002: Three-band Hubbard model for Na2IrO3: Topological insulator, zigzag antiferromagnet, and Kitaev-Heisenberg material Johannes Reuther, Manuel Laubach, Ronny Thomale, Stephan Rachel Na2IrO3 was one of the first materials proposed to feature the Kane-Mele-type topological insulator phase. Contemporaneously it was claimed that the same material is in a Mott insulating phase which is described by the Kitaev-Heisenberg (KH) model. First experiments indeed revealed Mott insulating behavior in conjunction with antiferromagnetic long-range order. Further refined experiments established antiferromagnetic order of zigzag type which is not captured by the KH model. Since then several extensions and modifications of the KH model were proposed in order to describe the experimental findings. Here we suggest that adding charge fluctuations to the KH model represents an alternative explanation of zigzag antiferromagnetism. Moreover, a phenomenological three-band Hubbard model unifies all the pieces of the puzzle: topological insulator physics for weak and KH model for strong electron-electron interactions as well as a zigzag antiferromagnet at intermediate interaction strength. |
Wednesday, March 7, 2018 8:24AM - 8:36AM |
K23.00003: High-field Magnetization Response as Evidence for Dominant Ferromagnetic Kitaev Correlations in the Alkali Iridate Na2IrO3 Sarbajaya Kundu, Sitikantha Das, Zengwei Zhu, Eundeok Mun, Ross McDonald, Gang Li, Luis Balicas, Alix McCollam, Gang Cao, Jeffrey Rau, Hae-Young Kee, Vikram Tripathi, Suchitra Sebastian
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Wednesday, March 7, 2018 8:36AM - 9:12AM |
K23.00004: Odd-parity electronic order in the strongly correlated and spin-orbit coupled metal Cd2Re2O7 Invited Speaker: John Harter Over the past several years, correlated electron systems with strong spin-orbit coupling have become a promising platform for realizing fundamentally new quantum states of matter. The majority of studies carried out in this burgeoning area have focused on exotic insulating phases such as topological Kondo insulators, Kitaev spin liquids, and topological Mott insulators. Recently, however, it has been theoretically predicted that novel metallic phases can also emerge in this regime. These newly predicted phases are characterized by spontaneously broken spatial inversion symmetry and are composed of charge carriers that exhibit spin-momentum locking and associated Fermi surface spin textures. Beyond their interest as fundamentally new states of matter, parity-odd electronic liquids are also predicted to be gateways to other exotic phases such as topological superconductivity. In this talk, I will discuss the first experimental observation of such odd-parity electronic order in the strongly spin-orbit coupled correlated metal Cd2Re2O7 using optical second harmonic generation. I will also discuss our use of coherent phonon spectroscopy to uncover an intricate coupling between the electronic and lattice degrees of freedom in this material, leading to phonons with a diverging damping rate at the critical temperature of the phase transition. |
Wednesday, March 7, 2018 9:12AM - 9:24AM |
K23.00005: Quantum oscillations in a pyrochlore superconductor Cd2Re2O7 Tomoya Asaba, Ziji Xiang, Colin Tinsman, Lu Chen, Jiaqiang Yan, Lu Li Metallic pyrochlore oxide Cd2Re2O7, the first superconductor in pyrochlore oxide family, shows a structural phase transition from cubic to tetragonal at Tc = 200 K. However, while the transport properties exhibit dramatic change across Tc, the lattice parameter change is extremely small and the electron correlation is argued as a driving force of the phase transition. Recently a multipolar nematic phase has been observed by second harmonic generation, proving this theory. Despite the interest in this material, no experimental Fermiology has been reported so far. We report the first observation of de Haas van Alphen quantum oscillations in single crystals of Cd2Re2O7 by torque magnetometry. The angular dependence of oscillation patterns and its comparison to the theoretical prediction will be discussed. |
Wednesday, March 7, 2018 9:24AM - 9:36AM |
K23.00006: Persistent spin texture enforced by symmetry Lingling Tao, Evgeny Tsymbal Persistent spin texture is the property of some materials to maintain a uniform spin configuration in momentum space. This property is predicted to support an extraordinarily long spin lifetime of carriers promising for spintronics applications. The persistent spin texture is known to emerge when the the Rashba and linear Dresselhaus SOC, are equal. This condition, however, is not trivial to achieve and requires tuning the Rashba and Dresselhaus parameters, as has been demonstrated using semiconductor quantum-well structures. Here we predict that there exist a class of non-centrosymmetric bulk materials where the persistent spin texture is enforced by the non-symmorphic space-group symmetry of the crystal. At certain high symmetry points in the Brillouin zone, the SOC combined with the lattice degrees of freedom imposes a constraint on the effective Hamiltonian, which only retains terms with the spin-orbit field independent of the momentum orientation, thus maintaining the persistent spin texture. We illustrate this behavior using density-functional theory calculations for bulk perovskite BiInO3, which reveals the persistent spin texture at the conduction band minimum. Our results broaden the range of materials which can be employed in spintronics. |
Wednesday, March 7, 2018 9:36AM - 9:48AM |
K23.00007: A Possible Spin-Orbit Coupling Assisted Semiconductor in ALaNiOsO6 (A=Sr, Ba) Dinesh Yadav, Sunil Lamichhane, Shalika Bhandari, Bishnu Belbase, Gopi Chandra Kaphle, Madhav Ghimire Double perovskites are found to exhibit novel properties desirable in spintronic applications. Here, by means of density functional theory calculations, we investigate the electronic and magnetic properties of newly synthesized ALaNiOsO6 (where A=Sr, Ba). We found the magnetic phase transition in these materials. The calculated total energy indicates antiferromagnetic ground state for SrLaNiOsO6 and ferromagnetic ground state for BaLaNiOsO6 with their easy axis along [010] directions, respectively. Both materials shows Mott insulating behavior with dominant contributions from Os-5d bands around the Fermi level. The sizable strength of spin-orbit coupling in Os plays significant role in opening the band gap in these compounds. Our results agrees with the experimental findings (0.3 eV) for both the materials. Furthermore, we predict a possible meta-magnetic transition in BaLaNiOsO6 similar to the Dirac Mott insulator Ba2NiOsO6. |
Wednesday, March 7, 2018 9:48AM - 10:00AM |
K23.00008: Increased terahertz conductivity with magnetic disorder in the 5d-oxide double perovskite family Sr2-xCaxCoOsO6 Matthew Warren, Jie Xiong, Ryan Morrow, Phuong Tran, Patrick Woodward, Rolando Valdes Aguilar We present the results of the terahertz (THz) conductivity studies in the double perovskite family of 5d-oxides Sr2-xCaxCoOsO6. As a function of composition x, this family of double perovskites undergoes a transformation from robust antiferromagnetic order at x=0, to spin glasses at x=1, and then eventually to a ferrimagnetic state at x=2. We find that concomitant with these changes is the steady increase of the THz conductivity that cannot be explained with the expected changes to the optical phonon frequency with composition. We discuss the possibility of these changes being associated with the increase of magnetic disorder as a function of composition, particularly around x=1. |
Wednesday, March 7, 2018 10:00AM - 10:12AM |
K23.00009: Spin-orbit coupling and electronic correlations in Hund's metals: Sr2RuO4 Minjae Kim, Jernej Mravlje, Michel Ferrero, Olivier Parcollet, Antoine Georges We investigate the interplay of spin-orbit coupling (SOC) and Hund's rule coupling driven electronic correlations in Sr2RuO4 using dynamical mean-field theory. We find that the orbital-diagonal components of the dynamical electronic correlations are unaffected by the SOC, which validates the concept of a Hund’s metal in the presence of SOC. In contrast, SOC itself is enhanced by approximately a factor of two by electronic correlations. We introduce the concept of an energy-dependent quasiparticle SOC, which is found to be essential in accounting simultaneously for: (i) the Fermi surface (ii) the low-energy dispersion of quasiparticles and (iii) the splitting between bands at higher binding energy. Our calculations are in good agreement with available experimental data. References: [1-4] |
Wednesday, March 7, 2018 10:12AM - 10:24AM |
K23.00010: Abstract Withdrawn
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Wednesday, March 7, 2018 10:24AM - 11:00AM |
K23.00011: Electrical control of spin-texture in non-magnetic ferroelectric oxide-based systems Invited Speaker: Silvia Picozzi Upon inversion symmetry breaking, spin-orbit coupling allows for spin-dependent electronic structures, even in the absence of long-range magnetic ordering. Given the prerequisite of showing a polar axis (in addition to being non-centrosymmetric), ferroelectrics are not only natural candidates for this kind of phenomena, but they also offer intriguing perspectives to control/induce/switch spin-textures with an electric field that switches the ferroelectric polarization. I will focus on several types of mechanisms to achieve the goal, ranging from Rashba spin-splitting to spin-valley coupling, with possible links to topologically non-trivial behaviour. Based on density functional simulations, I will show several realizations in ferroelectric oxide-based systems, where the k-dependent spin texture is one-to-one linked to polarization. |
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