Engineering a Spin-Orbital Magnetic Insulator by Tailoring SuperlatticesMatsuno, J.; Ihara, K.; Yamamura, S.; Wadati, H.; Ishii, K.; Shankar, V. V.; Kee, Hae-Young; Takagi, H.
doi: 10.1103/PhysRevLett.114.247209pmid: 26197009
In 5 d Ir oxides with an interplay of spin-orbit coupling and electron correlations, we have tailored a spin-orbital magnetic insulator out of a semimetal SrIrO 3 by tuning the structure through superlattices ( ( SrIrO 3 ) m , SrTiO 3 ) ( m = 1 , 2 , 3 , 4 , and ∞ ). We observed the systematic decrease of the magnetic ordering temperature and the resistivity as a function of m . The transition from the semimetal to the insulator is found to be closely linked to the appearance of magnetism at m ≃ 3 . Long range magnetic ordering was realized even in the m = 1 single layer superlattice, implying that the design and realization of novel electronic phases is feasible at the level of a single atomic layer in complex Ir oxides.
Tuning the Magnetic Anisotropy at a Molecule-Metal InterfaceBairagi, K.; Bellec, A.; Repain, V.; Chacon, C.; Girard, Y.; Garreau, Y.; Lagoute, J.; Rousset, S.; Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D.; Smogunov, A.; Barreteau, C.
doi: 10.1103/PhysRevLett.114.247203pmid: 26197003
We demonstrate that a C 60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C 60 / Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the C 60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C 60 p z and Co d z 2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C 60 with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material–ferromagnet systems.
Multiboson Correlation Interferometry with Arbitrary Single-Photon Pure StatesTamma, Vincenzo; Laibacher, Simon
doi: 10.1103/PhysRevLett.114.243601pmid: 26196976
We provide a compact full description of multiboson correlation measurements of arbitrary order N in passive linear interferometers with arbitrary input single-photon pure states. This allows us to physically analyze the novel problem of multiboson correlation sampling at the output of random linear interferometers. Our results also describe general multiboson correlation landscapes for an arbitrary number of input single photons and arbitrary interferometers. In particular, we use two different schemes to demonstrate, respectively, arbitrary-order quantum beat interference and 100% visibility entanglement correlations even for input photons distinguishable in their frequencies.
Affleck-Kennedy-Lieb-Tasaki State on a Honeycomb Lattice from t 2 g OrbitalsKoch-Janusz, Maciej; Khomskii, D. I.; Sela, Eran
doi: 10.1103/PhysRevLett.114.247204pmid: 26197004
The two-dimensional Affleck-Kennedy-Lieb-Tasaki (AKLT) model on a honeycomb lattice has been shown to be a universal resource for quantum computation. In this valence bond solid, however, the spin interactions involve higher powers of the Heisenberg coupling ( S → i · S → j ) n , making these states seemingly unrealistic on bipartite lattices, where one expects a simple antiferromagnetic order. We show that those interactions can be generated by orbital physics in multiorbital Mott insulators. We focus on t 2 g electrons on the honeycomb lattice and propose a physical realization of the spin- 3 / 2 AKLT state. We find a phase transition from the AKLT to the Néel state on increasing Hund’s rule coupling, which is confirmed by density matrix renormalization group simulations. An experimental signature of the AKLT state consists of protected, free S = 1 / 2 spins on lattice vacancies, which may be detected in the spin susceptibility.
Antiferromagnetic Dichroism in a Complex Multisublattice Magnetoelectric CuB 2 O 4Boldyrev, K. N.; Pisarev, R. V.; Bezmaternykh, L. N.; Popova, M. N.
doi: 10.1103/PhysRevLett.114.247210pmid: 26197010
Magnetic control of the crystal chirality was announced by Saito et al. ( Phys. Rev. Lett. 101 , 117402 ( 2008 ) ) on the ground of experiments in Cu B 2 O 4 . This claim has raised a sharp dispute in the literature because it seemed to contradict the fundamental symmetry principles. We settle this dispute on the basis of a high-resolution optical spectroscopy study of excitonic transitions in Cu B 2 O 4 . We find that a large sublattice-sensitive antiferromagnetic linear dichroism (LD) emerges at the Néel temperature T N = 2 1 K and show how it could simulate a “magnetic-field control of the crystal chirality.” We prove that the discovered LD is related microscopically to the magnetic Davydov splitting. This LD is highly sensitive to subtle changes in the spin subsystems, which allowed us to observe a splitting of the phase transition into an incommensurate magnetic phase into two transitions ( T 1 * = 8.5 and T 2 * = 7.9 K ) and to suggest elliptical spiral structures below T 1 * , instead of a simple circular helix proposed earlier.
Mutual Independence of Critical Temperature and Superfluid Density under Pressure in Optimally Electron-Doped Superconducting LaFeAsO 1 - x F xPrando, G.; Hartmann, Th.; Schottenhamel, W.; Guguchia, Z.; Sanna, S.; Ahn, F.; Nekrasov, I.; Blum, C. G. F.; Wolter, A. U. B.; Wurmehl, S.; Khasanov, R.; Eremin, I.; Büchner, B.
doi: 10.1103/PhysRevLett.114.247004pmid: 26196999
The superconducting properties of LaFeAsO 1 - x F x under conditions of optimal electron doping are investigated upon the application of external pressure up to ∼ 23 kbar . Measurements of muon-spin spectroscopy and dc magnetometry evidence a clear mutual independence between the critical temperature T c and the low-temperature saturation value for the ratio n s / m * (superfluid density over effective band mass of Cooper pairs). Remarkably, a dramatic increase of ∼ 30 % is reported for n s / m * at the maximum pressure value while T c is substantially unaffected in the whole accessed experimental window. We argue and demonstrate that the explanation for the observed results must take the effect of nonmagnetic impurities on multiband superconductivity into account. In particular, the unique possibility to modify the ratio between intraband and interband scattering rates by acting on structural parameters while keeping the amount of chemical disorder constant is a striking result of our proposed model.
Observation of Localized States in Lieb Photonic LatticesVicencio, Rodrigo A.; Cantillano, Camilo; Morales-Inostroza, Luis; Real, Bastián; Mejía-Cortés, Cristian; Weimann, Steffen; Szameit, Alexander; Molina, Mario I.
doi: 10.1103/PhysRevLett.114.245503pmid: 26196986
We present the first experimental demonstration of a new type of localized state in the continuum, namely, compacton-like linear states in flat-band lattices. To this end, we employ photonic Lieb lattices, which exhibit three tight-binding bands, with one being perfectly flat. Discrete predictions are confirmed by realistic continuous numerical simulations as well as by direct experiments. Our results could be of great importance for fundamental physics as well as for various applications where light needs to be conducted in a diffractionless and localized manner over long distances.
Triangular Spin-Orbit-Coupled Lattice with Strong Coulomb Correlations: Sn Atoms on a SiC(0001) SubstrateGlass, S.; Li, G.; Adler, F.; Aulbach, J.; Fleszar, A.; Thomale, R.; Hanke, W.; Claessen, R.; Schäfer, J.
doi: 10.1103/PhysRevLett.114.247602pmid: 26197013
Two-dimensional (2D) atom lattices provide model setups with Coulomb correlations that induce competing ground states. Here, SiC emerges as a wide-gap substrate with reduced screening. We report the first artificial high- Z atom lattice on SiC(0001) by Sn adatoms, based on experimental realization and theoretical modeling. Density-functional theory of our triangular structure model closely reproduces the scanning tunneling microscopy. Photoemission data show a deeply gapped state ( ∼ 2 eV gap), and, based on our calculations including dynamic mean-field theory, we argue that this reflects a pronounced Mott-insulating scenario. We also find indications that the system is susceptible to antiferromagnetic superstructures. Such artificial lattices on SiC(0001) thus offer a novel platform for coexisting Coulomb correlations and spin-orbit coupling, with bearing for unusual magnetic phases and proposed topological quantum states of matter.
Narrow Magnonic Waveguides Based on Domain WallsGarcia-Sanchez, Felipe; Borys, Pablo; Soucaille, Rémy; Adam, Jean-Paul; Stamps, Robert L.; Kim, Joo-Von
doi: 10.1103/PhysRevLett.114.247206pmid: 26197006
The channeling of spin waves with domain walls in ultrathin ferromagnetic films is demonstrated theoretically and through micromagnetics simulations. It is shown that propagating excitations localized to the wall, which appear in the frequency gap of bulk spin wave modes, can be guided in curved geometries and propagate in close proximity to other channels. For Néel-type walls arising from a Dzyaloshinskii-Moriya interaction, the channeling is strongly nonreciprocal and group velocities can exceed 1 km / s in the long wavelength limit for certain propagation directions. The channeled modes represent an unusual analogy of whispering gallery waves that are one dimensional and nonreciprocal with this interaction. Moreover, a sufficiently strong Dzyaloshinskii-Moriya interaction can create a degeneracy of channeled and propagating modes at a critical wave vector.