Direct Observation of Magnon Fractionalization in the Quantum Spin Ladder (2008)
Thielemann, B., Rüegg, Ch., Rønnow, H. M., Läuchli, A. M., Normand, B., ...
We measure by inelastic neutron scattering the spin excitation spectra as a function of applied magnetic field in the quantum spin-ladder material (C5H12N)2CuBr4. Discrete magnon modes at low fields...
Field-Controlled Magnetic Order in the Quantum Spin-Ladder System (Hpip)2CuBr4 (2008)
Thielemann, B., Rüegg, Ch., Kiefer, K., Rønnow, H. M., Normand, B., Bouillot, P., ...
Neutron diffraction is used to investigate the field-induced, antiferromagnetically ordered state in the two-leg spin-ladder material (Hpip)2CuBr4. This "classical" phase, a consequence of weak...
Thermodynamics of the Spin Luttinger-Liquid in a Model Ladder Material (2008)
Rüegg, Ch., Kiefer, K., Thielemann, B., McMorrow, D. F., Zapf, V., Normand, B., ...
The phase diagram in temperature and magnetic field of the metal-organic, two-leg, spin-ladder compound (C5H12N)2CuBr4 is studied by measurements of the specific heat and the magnetocaloric effect....
Quantum Magnets under Pressure: Controlling Elementary Excitations in TlCuCl3 (2008)
Rüegg, Ch., Normand, B., Matsumoto, M., Furrer, A., McMorrow, D., Krämer, K., ...
We follow the evolution of the elementary excitations of the quantum antiferromagnet TlCuCl3 through the pressure-induced quantum critical point, which separates a dimer-based quantum disordered...
Static impurities in the S=3/2 kagome lattice (2007)
Laeuchli, A., Dommange, S., Normand, B., Mila, F.
We consider the effects of doping the S=3/2 kagome lattice with static, nonmagnetic impurities. By exact diagonalization calculations on small clusters we deduce the local spin correlations and...
Multiple magnon modes and consequences for the Bose-Einstein condensed phase in BaCuSi2O6 (2007)
Ruegg, Ch., McMorrow, D. F., Normand, B., Ronnow, H. M., Sebastian, S. E., Fisher, I. R., ...
The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S=1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering...
Multiple Magnon Modes and Consequences for the Bose-Einstein Condensed Phase in BaCuSi2O6 (2006)
Rüegg, Ch., McMorrow, D. F., Normand, B., Ronnow, H. M., Sebastian, S. E., Fisher, I. R., ...
The compound BaCuSi2O6 is a quantum magnet with antiferromagnetic dimers of S = 1/2 moments on a quasi-2D square lattice. We have investigated its spin dynamics by inelastic neutron scattering...
High-dimensional fractionalization and spinon deconfinement in pyrochlore antiferromagnets (2006)
Nussinov, Z., Batista, C. D., Normand, B., Trugman, S. A.
The ground states of Klein type spin models on the pyrochlore and checkerboard lattice are spanned by the set of singlet dimer coverings, and thus possess an extensive ground--state degeneracy. Among...
Quantum statistics of interacting dimer spin systems (2005)
Ruegg, C., Normand, B., Matsumoto, M., Niedermayer, A., Furrer, A., Kramer, K.W., ...
The compound TlCuCl3 represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron...
Quantum phase diagram of the generalized ionic Hubbard model for AB$_{n}$ chains (2005)
Torio, M. E., Aligia, A. A., Japaridze, G. I., Normand, B.
We investigate the ground-state phase diagram of the Hubbard model for the AB$_{N-1}$ chain with filling 1/N, where $N$ is the number of atoms per unit cell. In the strong-coupling limit, a charge...
Quantum Statistics of Interacting Dimer Spin Systems (2005)
Rüegg, Ch., Normand, B., Matsumoto, M., Niedermayer, Ch., Furrer, A., Krämer, K. W., ...
The compound TlCuCl3 represents a model system of dimerized quantum spins with strong interdimer interactions. We investigate the triplet dispersion as a function of temperature by inelastic neutron...
Exchange constants and spin dynamics in Mn12-acetate (2004)
Honecker, A., Fukushima, N., Normand, B., Chaboussant, G.
We have obtained new inelastic neutron scattering (INS) data for the molecular magnet Mn12-acetate which exhibit at least six magnetic peaks in the energy range 5-35 meV. These are compared with a...
Detection of topological transitions by transport through molecules and nanodevices (2004)
Aligia, A. A., Hallberg, K., Normand, B., Kampf, A. P.
We analyze the phase transitions of an interacting electronic system weakly coupled to free-electron leads by considering its zero-bias conductance. This is expressed in terms of two effective...
Spin-charge separation in Aharonov-Bohm rings of interacting electrons (2004)
Hallberg, K., Aligia, A. A., Kampf, A. P., Normand, B.
We investigate the properties of strongly correlated electronic models on a flux-threaded ring connected to semi-infinite free-electron leads. The interference pattern of such an Aharonov-Bohm ring...
Exchange Interactions and High-Energy Spin States in Mn_12-acetate (2004)
Chaboussant, G., Sieber, A., Ochsenbein, S., Murrie, M., Honecker, A., ...
We perform inelastic neutron scattering measurements on the molecular nanomagnet Mn_12-acetate to measure the excitation spectrum up to 45meV (500K). We isolate magnetic excitations in two groups at...
Circulating-current states and ring-exchange interactions in cuprates (2004)
We consider the consequences for circulating-current states of a cyclic, four-spin, ``ring-exchange'' interaction of the type shown recently to be significant in cuprate systems. The real-space...
Phase Diagram of the Heisenberg Spin Ladder with Ring Exchange (2003)
Gritsev, V., Normand, B., Baeriswyl, D.
We investigate the phase diagram of a generalized spin-1/2 quantum antiferromagnet on a ladder with rung, leg, diagonal, and ring-exchange interactions. We consider the exactly soluble models...
Field- and pressure-induced magnetic quantum phase transitions in TlCuCl_3 (2003)
Matsumoto, M., Normand, B., Rice, T. M., Sigrist, M.
Thallium copper chloride is a quantum spin liquid of S = 1/2 Cu^2+ dimers. Interdimer superexchange interactions give a three-dimensional magnon dispersion and a spin gap significantly smaller than...
Static impurities in the kagome lattice: dimer freezing and mutual repulsion (2003)
Dommange, S., Mambrini, M., Normand, B., Mila, F.
We consider the effects of doping the S = 1/2 kagome lattice with static impurities. We demonstrate that impurities lower the number of low-lying singlet states, induce dimer-dimer correlations of...
Solvent-induced micelle formation in a hydrophobic interaction model (2003)
Moelbert, S., Normand, B., Rios, P. De Los
We investigate the aggregation of amphiphilic molecules by adapting the two-state Muller-Lee-Graziano model for water, in which a solvent-induced hydrophobic interaction is included implicitly. We...
Kosmotropes and chaotropes: modelling preferential exclusion, binding and aggregate stability (2003)
Moelbert, Susanne, Normand, B., Rios, Paolo De Los
Kosmotropic cosolvents added to an aqueous solution promote the aggregation of hydrophobic solute particles, while chaotropic cosolvents act to destabilise such aggregates. We discuss the mechanism...
Normand, B, Zemke, WT, Côte, Renaud; U0051201, Pichler, M, Stwalley, WC
The weakly bound long range potential curves between a highly excited Cs* (ns, 8 less than or equal to n less than or equal to 20) atom and a ground state Cs atom are calculated using simple but...
Vertical and Diagonal Stripes in the Extended Hubbard Model (2002)
Raczkowski, M., Normand, B., Oles, A. M.
We extend previous real-space Hartree-Fock studies of static stripe stability to determine the phase diagram of the Hubbard model with anisotropic nearest-neighbor hopping t, by varying the on-site...
Magnon Dispersion in the Field-Induced Magnetically Ordered Phase of TlCuCl3 (2002)
Matsumoto, Masashige, Normand, B., Rice, T. M., Sigrist, Manfred
The magnetic properties of the interacting dimer system TlCuCl3 are investigated within a bond-operator formulation. The observed field-induced staggered magnetic order perpendicular to the field is...
Suppression of static stripe formation by next-neighbor hopping (2001)
We show from real-space Hartree-Fock calculations within the extended Hubbard model that next-nearest neighbor (t') hopping processes act to suppress the formation of static charge stripes. This...
Spin dynamics and coherent tunnelling in the molecular magnetic rings Fe_6 and Fe_8 (2001)
Honecker, A., Meier, F., Loss, Daniel, Normand, B.
We present detailed calculations of low-energy spin dynamics in the ``ferric wheel'' systems Na:Fe_6 and Cs:Fe_8 in a magnetic field. We compute by exact diagonalisation the low-energy spectra and...
We show that doping a Majumdar--Ghosh chain with non-magnetic impurities does {\it not} produce almost free spins 1/2. The difference between this system and other spin liquids, such as unfrustrated...
Lattice anisotropy as microscopic origin of static stripes in cuprates (2001)
Structural distortions in cuprate materials offer a microscopic origin for anisotropies in electron transport in the basal plane. Using a real-space Hartree-Fock approach, we consider the ground...
Baseline assessment in Scotland: an analysis of pilot data (2001)
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
In preparation for the possible future introduction of a Scottish system of baseline assessment, a prototype scheme was trialled early in 1998 in samples of pre-school centres and Primary 1 classes,...
Baseline assessment in Scotland: an evaluation of pilot procedures (2001)
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
No abstract available.
Magnetization in Molecular Iron Rings (2000)
Normand, B., Wang, X., Zotos, X., Loss, Daniel
The organometallic ring molecules Fe_6 and Fe_10 are leading examples of a class of nanoscopic molecular magnets, which have been of intense recent interest both for their intrinsic magnetic...
Island phases and charge order in two-dimensional manganites (2000)
Aliaga, H., Normand, B., Hallberg, K., Avignon, M., Alascio, B.
The ferromagnetic Kondo lattice model with an antiferromagnetic interaction between localized spins is a minimal description of the competing kinetic t and magnetic K energy terms which generate the...
Magnetic properties of (VO)_2P_2O_7: two-plane structure and spin-phonon interactions (2000)
Detailed experiments on single-crystal (VO)_2P_2O_7 continue to reveal new and unexpected features. We show that a model composed of two, independent planes of spin chains with frustrated magnetic...
Order by disorder from non-magnetic impurities in a two-dimensional quantum spin liquid (2000)
Wessel, S., Normand, B., Sigrist, M., Haas, S.
We consider doping of non-magnetic impurities in the spin-1/2, 1/5-depleted square lattice. This structure, whose undoped phase diagram offers both magnetically ordered and spin-liquid ground states,...
Nonlinear sigma Model Treatment of Quantum Antiferromagnets in a Magnetic Field (1999)
Normand, B., Kyriakidis, Jordan, Loss, Daniel
We present a theoretical analysis of the properties of low-dimensional quantum antiferromagnets in applied magnetic fields. In a nonlinear sigma model description, we use a spin stiffness analysis, a...
On possible superconductivity in the doped ladder compound La_(1-x)Sr_xCuO_2.5 (1998)
Normand, B., Agterberg, D. F., Rice, T. M.
LaCuO_2.5 is a system of coupled, two-chain, cuprate ladders which may be doped systematically by Sr substitution. Motivated by the recent synthesis of single crystals, we investigate theoretically...
Magnetic Properties of (VO)_2P_2O_7 from Frustrated Interchain Coupling (1998)
Neutron-scattering experiments on (VO)_2P_2O_7 reveal both a gapped magnon dispersion and an unexpected, low-lying second mode. The proximity and intensity of these modes suggest a frustrated...
Quantum Antiferromagnets in a Magnetic Field (1998)
Motivated by recent experiments on low-dimensional quantum magnets in applied magnetic fields, we present a theoretical analysis of their properties based on the nonlinear sigma model. The spin...
Magnetic properties of the coupled ladder system MgV$_2$O$_5$ (1998)
Millet, P., Satto, C., Bonvoisin, J., Normand, B., Penc, K., Albrecht, M., ...
We present magnetic susceptibility measurements on MgV$_2$O$_5$, a compound in which the vanadium oxide planes have the same topology as in CaV$_2$O$_5$. The most striking property is that there is...
Phase Diagram of the S = 1/2 Frustrated Coupled Ladder System (1997)
Normand, B., Penc, K., Albrecht, M., Mila, F.
We present a theoretical study of the magnetic phase diagram of the frustrated coupled ladder structure realized recently in several materials. This system displays a nondegenerate spin-gap state in...
For a system of two-chain spin ladders, the ground state for weak interladder coupling is the spin-liquid state of the isolated ladder, but is an ordered antiferromagnet (AF) for sufficiently large...
Electronic and Magnetic Structure of LaCuO$_{2.5}$ (1996)
The recently-discovered ``ladder'' compound LaCuO$_{2.5}$ has been found to admit hole doping without altering its structure of coupled copper oxide ladders. While susceptibility measurements on the...
Dynamic Susceptibility and Phonon Anomalies in the Bilayer $t$-$J$ Model (1995)
Normand, B., Kohno, H., Fukuyama, H.
We consider a bilayer version of the extended $t$-$J$ model, with a view to computing the form of certain experimentally observable properties. Using the slave-boson decomposition, we show at the...
Spin-Phonon Coupling in the Single-Layer Extended t-J Model (1995)
Normand, B., Kohno, H., Fukuyama, H.
We consider the implications of spin-phonon coupling within the slave-boson, mean-field treatment of the extended t-J model of a high-temperature superconductor. In bilayer cuprates such as YBaCuO,...
Superconductive Phonon Anomalies in High-$T_c$ Cuprates (1994)
Normand, B., Kohno, H., Fukuyama, H.
We consider the effects on phonon dynamics of spin-lattice coupling within the slave-boson mean-field treatment of the extended $t$-$J$ model. With no additional assumptions the theory is found to...
Littlewood, P., Millis, A., Zhu, X., Normand, B.
We present the theory of the dynamics of a two-dimensional Wigner crystal in a high magnetic field, assuming charge-density-wave correlations extend over a distance large compared to the...
Littlewood, P., Millis, A., Zhu, X., Normand, B.
We present the theory of the dynamics of a two-dimensional Wigner crystal in a high magnetic field, assuming charge-density-wave correlations extend over a distance large compared to the...
Littlewood, P., Millis, A., Zhu, X., Normand, B.
We present the theory of the dynamics of a two-dimensional Wigner crystal in a high magnetic field, assuming charge-density-wave correlations extend over a distance large compared to the...
Baseline Assessment in Scotland: an analysis of pilot data
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
In preparation for the possible future introduction of a Scottish system of baseline assessment, a prototype scheme was trialled early in 1998 in samples of pre-school centres and Primary 1 classes,...
Baseline assessment in Scotland: an evaluation of pilot procedures
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
No abstract available.
Baseline Assessment in Scotland: an analysis of pilot data
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
In preparation for the possible future introduction of a Scottish system of baseline assessment, a prototype scheme was trialled early in 1998 in samples of pre-school centres and Primary 1 classes,...
Baseline assessment in Scotland: an evaluation of pilot procedures
Wilkinson, J.E., Johnson, S., Watt, J., Napuk, A., Normand, B.
No abstract available.