Benjamin Canals

Publications (10)2.55 Total impact

• Source

  Available from: Mathieu Taillefumier

  Article: Chiral two-dimensional electron gas in a periodic magnetic field

  Mathieu Taillefumier, Vitalii Dugaev, Benjamin Canals, Claudine Lacroix, Patrick Bruno
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  ABSTRACT: We study the energy spectrum and electronic properties of two-dimensional electron gas in a periodic magnetic field of zero average with a symmetry of triangular lattice. We demonstrate how the structure of electron energy bands can be changed with the variation of the field strength, so that we can start from nearly free electron gas and then transform it continuously to a system of essentially localized chiral electron states. We find that the electrons near some minima of the effective potential are responsible for occurrence of dissipationless persistent currents creating a lattice of current contours. The topological properties of the electron energy bands are also varied with the intensity of periodic field. We calculated the topological Chern numbers of several lower energy bands as a function of the field. The corresponding Hall conductivity is nonzero and, when the Fermi level lies in the gap, it is quantized.
  08/2008;
• Source

  Available from: Mathieu Taillefumier

  Article: Anomalous Hall Effect due to the spin chirality in the Kagom\'{e} lattice

  Mathieu Taillefumier, Benjamin Canals, Claudine Lacroix, Vitalii Dugaev, Patrick Bruno
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  ABSTRACT: We consider a model for a two dimensional electron gas moving on a kagom\'{e} lattice and locally coupled to a chiral magnetic texture. We show that the transverse conductivity $\sigma\_{xy}$ does not vanish even if spin-orbit coupling is not present and it may exhibit unusual behavior. Model parameters are the chirality, the number of conduction electrons and the amplitude of the local coupling. Upon varying these parameters, a topological transition characterized by change of the band Chern numbers occur. As a consequence, $\sigma\_{xy}$ can be quantized, proportional to the chirality or have a non monotonic behavior upon varying these parameters. Comment: 8 pages, 7 figures
  01/2006;
• Article: Ordering in pyrochlore compounds due to Dzyaloshinsky–Moriya interactions: the case of Cu4O3

  Maged Elhajal, Benjamin Canals, Claudine Lacroix
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  ABSTRACT: We investigate the effects of Dzyaloshinsky–Moriya interactions (DMI) on the magnetic properties of the pyrochlore antiferromagnet. The relevance of this interaction for such a system is shown and we describe how to take it into account in accordance with the symmetries of the pyrochlore lattice. A phase transition from a high temperature paramagnetic phase to a low temperature long range ordered state takes place as soon as DMI are present. We describe the different magnetic structures obtained depending on the geometry of the DMI and special attention is given to the compound Cu4O3 for which a possible explanation of the experimentally observed ordering is given.
  Journal of Physics Condensed Matter 03/2004; 16(11):S917. · 2.55 Impact Factor
• Source

  Available from: ArXiv

  Article: Dzyaloshinski-Moriya interactions in the kagome lattice

  Maged Elhajal, Benjamin Canals, Claudine Lacroix
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  ABSTRACT: The kagom\'e lattice exhibits peculiar magnetic properties due to its strongly frustated cristallographic structure, based on corner sharing triangles. For nearest neighbour antiferromagnetic Heisenberg interactions there is no Neel ordering at zero temperature both for quantum and classical s pins. We show that, due to the peculiar structure, antisymmetric Dzyaloshinsky-Moriya interactions (${\bf D} . ({\bf S}_i \times {\bf S}_j)$) are present in this latt ice. In order to derive microscopically this interaction we consider a set of localized d-electronic states. For classical spins systems, we then study the phase diagram (T, D/J) through mean field approximation and Monte-Carlo simulations and show that the antisymmetric interaction drives this system to ordered states as soon as this interaction is non zero. This mechanism could be involved to explain the magnetic structure of Fe-jarosites. Comment: 4 pages, 2 figures. Presented at SCES 2001
  08/2001;
• Source

  Available from: arxiv.org

  Article: Comparison of several tetrahedra-based lattices

  Maged Elhajal, Benjamin Canals, Claudine Lacroix
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  ABSTRACT: A comparison of the quantum Heisenberg antiferromagnetic model (QHAM) on the pyrochlore lattice, the checkerboard lattice and the square lattice with crossing interactions is performed. The three lattices are constructed with the same tetrahedral unit cell and this property is used to describe the low energy spectrum by means of an effective hamiltonian restricted to the singlet sector. We analyze the structure of the effective hamiltonian and solve it within mean field approximation for the three lattices. Comment: 7 pages (latex), 2 figures. Submitted to Canadian Journal of Physics for the proceedings of the Highly Frustrated Magnetism 2000 Conference, Waterloo, Ontario, Canada, June 11-15, 2000
  04/2001;
• Source

  Available from: ArXiv

  Article: Spin Liquid Phase in the Pyrochlore Antiferromagnet

  Benjamin Canals, Dmitry Garanin
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  ABSTRACT: Correlation functions (CFs) of the classical Heisenberg antiferromagnet on the pyrochlore lattice are studied by solving exactly the infinite-component spin-vector model. % As in many Fully Frustrated Lattices, the constraint due to the minimization of the energy and the particular structure based on corner sharing tetrahedra both contribute to the creation of local degrees of freedom. % The resulting degeneracy destroys any magnetic order at all temperature and we obtain no sign of criticality, even at $T = 0$. % Calculated neutron scattering cross sections have their maxima beyond the first Brillouin Zone and reproduce experimental results obtained on Y(Sc)Mn$_2$ and CsCrNiF$_6$ as well as theoretical predictions previously obtained by classical Monte Carlo simulations. % Evidences for thermal and spatial decoupling of the magnetic modes are found so that the magnetic fluctuations in this system can be approximated by $S(q,T) \approx f(q) h(T)$. Comment: 6 pages (revtex two columns), 7 figures. Submitted to Canadian Journal of Physics for the Proceedings of the Higly Frustrated Magnetism 2000 Conference, Waterloo, Ontario, Canada, June 11-15, 2000
  02/2001;
• Article: Mean-field study of the disordered ground state in the β-Mn lattice

  Benjamin Canals, Claudine Lacroix
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  ABSTRACT: The type-II atoms in the β phase of manganese form a three-dimensional network of corner-sharing triangles in a cubic symmetry. This peculiar geometry induces a very strong topological frustration that can explain the absence of magnetic ordering in the β phase of manganese. Within a mean-field theory, we show that the classical antiferromagnetic Heisenberg model with nearest-neighbor interactions exhibits a line of zero energy modes. Thus this model does not order at any temperature on this lattice in the mean-field approximation. Longer-range interactions or slight deformations do not always remove the ground-state degeneracy, and the model will order only for peculiar sets of exchange parameters.
  Phys. Rev. B. 04/2000; 61(17).
• Source

  Available from: arxiv.org

  Article: Pyrochlore Antiferromagnet: A Three-Dimensional Quantum Spin Liquid

  Benjamin Canals, Claudine Lacroix
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  ABSTRACT: The quantum pyrochlore antiferromagnet is studied by perturbative expansions and exact diagonalization of small clusters. We find that the ground state is a spin-liquid state: The spin-spin correlation functions decay exponentially with distance and the correlation length never exceeds the interatomic distance. The calculated magnetic neutron diffraction cross section is in very good agreement with experiments performed on Y(Sc)Mn2. The low energy excitations are singlet-singlet ones, with a finite spin gap. Comment: 4 pages, 4 figures
  07/1998;
• Source

  Available from: arxiv.org

  Article: Kondo Screening and Magnetic Ordering in Frustrated UNi4B

  Claudine Lacroix, Benjamin Canals, M. D. Nunez-Regueiro
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  ABSTRACT: UNi4B exhibits unusual properties and, in particular, a unique antiferromagnetic arrangement involving only 2/3 of the U sites. Based on the low temperature behavior of this compound, we propose that the remaining 1/3 U sites are nonmagnetic due to the Kondo effect. We derive a model in which the coexistence of magnetic and nonmagnetic U sites is the consequence of the competition between frustration of the crystallographic structure and instability of the 5f moments. Comment: 4 pages, 2 figures
  07/1998;
• Article: Quantum spin liquid: The Heisenberg antiferromagnet on the three-dimensional pyrochlore lattice

  Benjamin Canals, Claudine Lacroix
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  ABSTRACT: We calculate the correlation functions of the S=1/2 Heisenberg antiferromagnet on the three-dimensional pyrochlore lattice. We use a perturbative expansion in terms of spin blocks. This method is self-controlled by the extracted correlation length. We find that the ground state is a spin-liquid state: the spin-spin correlation functions decay exponentially with distance and the correlation length never exceeds the interatomic distance, even at T=0. The static structure factor becomes dispersive, indicating a selection of modes by thermal and quantum fluctuations. We also calculate the magnetic neutron diffraction cross section in two planes of the reciprocal space and we find a very good agreement with neutron experiments performed on Y(Sc)Mn2 and CsNiCrF6.
  Phys. Rev. B. 61(2).