G. Batrouni - Academia.edu (original) (raw)
Papers by G. Batrouni
Conclusion 87 Conclusion en français 91 Bibliography 95 Abstract 107 is tuned, the system undergo... more Conclusion 87 Conclusion en français 91 Bibliography 95 Abstract 107 is tuned, the system undergoes a transition to an unexpected insulating paramagnetic state that involves atomic layers not directly at the interface, before another transition at large coupling in which the interface decouples from the bulk, the latter recovering its initial properties. The eect of the correlation strength and of the interface thickness on the propagation of the intermediate state into the materials will be nally discussed. The last chapter has our conclusions and perspectives for future work. Le dernier chapitre résume nos conclusions et les perspectives de développement ultérieur.
PACS. 05.40.Jc -Brownian motion. PACS. 82.70.Dd -Colloids. PACS. 67.40.Hf -Hydrodynamics in speci... more PACS. 05.40.Jc -Brownian motion. PACS. 82.70.Dd -Colloids. PACS. 67.40.Hf -Hydrodynamics in specific geometries, flow in narrow channels. Abstract. -Space-dependent diffusion of micrometer-sized particles has been directly observed using digital video microscopy. The particles were trapped between two nearly parallel walls making their confinement position dependent. Consequently, not only did we measure a diffusion coefficient which depended on the particles' position, but also report and explain a new effect: a drift of the particles' individual positions in the direction of the diffusion coefficient gradient, in the absence of any external force or concentration gradient. Brownian motion of spherical colloidal particles in the vicinity of a wall has been extensively studied, both theoretically [1-3] and experimentally In this article, we report some new experimental results concerning the Brownian motion of particles trapped between two nearly parallel walls, so that th...
Physical Review A, 2007
We study the effects of interaction between bosons and fermions in a Bose-Fermi mixtures loaded i... more We study the effects of interaction between bosons and fermions in a Bose-Fermi mixtures loaded in an optical lattice. We concentrate on the destruction of a bosonic Mott phase driven by repulsive interaction between bosons and fermions. Once the Mott phase is destroyed, the system enters a superfluid phase where the movements of bosons and fermions are correlated. We show that this phase has simultaneously correlations reminiscent of a conventional superfluid and of a pseudo-spin density wave order.
Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have... more Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have suggested that momentum dependence of the electron-phonon coupling plays an important role in their properties. Initial attempts to study Hamiltonians which either do not include or else truncate the range of Coulomb repulsion have noted that the resulting spatial non-locality of the electron-phonon interaction leads to a dominant tendency to phase separation. Here we present Quantum Monte Carlo results for such models in which we incorporate both on-site and intersite electron-electron interactions. We show that these can stabilize phases in which the density is homogeneous and determine the associated phase boundaries. As a consequence, the physics of momentum dependent electron-phonon coupling can be determined outside of the trivial phase separated regime.
Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have... more Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have suggested that momentum dependence of the electron-phonon coupling plays an important role in their properties. Initial attempts to study Hamiltonians which either do not include or else truncate the range of Coulomb repulsion have noted that the resulting spatial non-locality of the electron-phonon interaction leads to a dominant tendency to phase separation. Here we present Quantum Monte Carlo results for such models in which we incorporate both on-site and intersite electron-electron interactions. We show that these can stabilize phases in which the density is homogeneous and determine the associated phase boundaries. As a consequence, the physics of momentum dependent electron-phonon coupling can be determined outside of the trivial phase separated regime.
Bo Xiao, F. Hébert, G. Batrouni, 3, 4, 5, 6 and R.T. Scalettar Department of Physics, University ... more Bo Xiao, F. Hébert, G. Batrouni, 3, 4, 5, 6 and R.T. Scalettar Department of Physics, University of California, Davis, CA 95616,USA Université Côte d’Azur, CNRS, INPHYNI, France MajuLab, CNRS-UCA-SU-NUS-NTU International Joint Research Unit, 117542 Singapore Centre for Quantum Technologies, National University of Singapore, 2 Science Drive 3, 117542 Singapore Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore Beijing Computational Science Research Center, Beijing 100193, China (Dated: April 2, 2019)
AIP Conference Proceedings, 2003
We study the ground state properties of the 1-D boson and fermion Hubbard models in harmonic trap... more We study the ground state properties of the 1-D boson and fermion Hubbard models in harmonic traps with an underlying lattice. The physics of these systems is found to be fundamentally different from the homogeneous case. Global quantities lose their meaning and Mott domains appear for a continuous range of incommensurate fillings. A local order parameter is defined to characterize
Ultracold Gases and Quantum Information, 2011
Physical Review Letters, 2005
Physical Review Letters, 1994
Physical Review Letters, 2012
The nature of magnetic order and transport properties near surfaces is a topic of great current i... more The nature of magnetic order and transport properties near surfaces is a topic of great current interest. Here we model metal-insulator interfaces with a multi-layer system governed by a tightbinding Hamiltonian in which the interaction is non-zero on one set of adjacent planes and zero on another. As the interface hybridization is tuned, magnetic and metallic properties undergo an evolution that reflects the competition between anti-ferromagnetism and (Kondo) singlet formation in a scenario similar to that occurring in heavy-fermion materials. For a few-layer system at intermediate hybridization, a Kondo insulating phase results where magnetic order and conductivity are suppressed in all layers. As more insulating layers are added, magnetic order is restored in all correlated layers except that at the interface. Residual signs of Kondo physics are however evident in the bulk as a substantial reduction of the order parameter in the 2-3 layers immediately adjacent to the interfacial one. We find no signature of long range magnetic order in the metallic layers.
Physical Review E, 2002
We investigate numerically the failure process when two elastic media, one hard and one soft that... more We investigate numerically the failure process when two elastic media, one hard and one soft that have been glued together thus forming a common interface, are pulled apart. We present three main results: (1) The area distribution of simultaneously failing glue (bursts) follows a power law consistent with the theoretically expected exponent 2.5, (2) the maximum load and displacement before catastrophic failure scale as L 2 and L 0 respectively, where L is the linear size of the system, and (3) the area distribution of failed glue regions (clusters) is a power law with exponent −1.6 when the system fails catstrophically.
Physical Review B, 2005
We present Quantum Monte Carlo simulations of the soft-core bosonic Hubbard model with a ring exc... more We present Quantum Monte Carlo simulations of the soft-core bosonic Hubbard model with a ring exchange term K. For values of K which exceed roughly half the on-site repulsion U , the density is a non-monotonic function of the chemical potential, indicating that the system has a tendency to phase separate. This behavior is confirmed by an examination of the density-density structure factor at small momenta and real space images of the boson configurations. Adding a near-neighbor repulsion can compete with phase separation, but still does not give rise to a stable normal Bose liquid.
Physical Review B, 2009
We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantu... more We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantum Monte Carlo simulations. By increasing the interaction strength U (relative to the hopping parameter t) at half-filling and zero temperature, the system undergoes a quantum phase transition at 5.0 < Uc/t < 5.1 from a semi-metal to a phase displaying simultaneously superfluid behavior and density order. Doping away from half-filling, and increasing the interaction strength at finite but low temperature T , the system always appears to be a superfluid exhibiting a crossover between a BCS and a molecular regime. These different regimes are analyzed by studying the spectral function. The formation of pairs and the emergence of phase coherence throughout the sample are studied as U is increased and T is lowered.
Physical Review B, 2012
The low-temperature properties of the two-dimensional attractive Hubbard model are strongly influ... more The low-temperature properties of the two-dimensional attractive Hubbard model are strongly influenced by the fermion density. Away from half-filling, there is a finite-temperature transition to a phase with s-wave pairing order. However, Tc is suppressed to zero at half-filling, where long-range charge-density-wave order also appears, degenerate with superconductivity. This paper presents Determinant Quantum Monte Carlo simulations of the attractive Hubbard model in the presence of a confining potential Vtrap which makes the fermion density ρ inhomogeneous across the lattice. Pair correlations are shown to be large at low temperatures in regions of the trapped system with incommensurate filling, and to exhibit a minimum as the local density ρ(i) passes through one fermion per site. In this ring of ρ(i) = 1, charge order is enhanced. A comparison is made between treating Vtrap within the local-density approximation (LDA) and in an ab initio manner. It is argued that certain sharp features of the LDA result at integer filling do not survive the proximity of doped sites. The critical temperature of confined systems of fixed characteristic density is estimated.
Nuclear Physics B, 1982
ABSTRACT We extend Halpern's field-strength formulation and dual potentials (for continuu... more ABSTRACT We extend Halpern's field-strength formulation and dual potentials (for continuum gauge theories) to abelian and non-abelian lattice gauge theories. New results include: (i) plaquette formulation of all lattice gauge theories, (ii) the strong coupling expansion is seen as (a) a perturbation in dual links or (b) a gradual restoration of the lattice Bianchi identity. To leading order in the strong coupling expansion the lattice Bianchi identity is completely ignored. Geometrical interpretation of the lattice Bianchi identity is presented along with a discussion of the “abelianization” of the non-abelian identity and its connection with gauge-invariant variables. For abelian theories we also show that the dual potential is Fourier conjugate to the Bianchi identity and that the Coulomb gas representation of these theories is easily obtained in this formulation.
Journal of the Physical Society of Japan, 2005
We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, fo... more We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, focusing on the crossover from a gas of softcore bosons to a Tonks-Girardeau gas in a one-dimensional optical lattice. We find that depending on the quantity being measured, the behavior found in the Tonks-Girardeau regime is observed already at relatively small values of the interaction strength. A finite critical value for entering the Tonks-Girardeau regime does not exist. Furthermore, we discuss the computational efficiency of two quantum Monte Carlo methods to simulate large scale trapped bosonic systems: directed loops in stochastic series expansions and the worm algorithm.
Conclusion 87 Conclusion en français 91 Bibliography 95 Abstract 107 is tuned, the system undergo... more Conclusion 87 Conclusion en français 91 Bibliography 95 Abstract 107 is tuned, the system undergoes a transition to an unexpected insulating paramagnetic state that involves atomic layers not directly at the interface, before another transition at large coupling in which the interface decouples from the bulk, the latter recovering its initial properties. The eect of the correlation strength and of the interface thickness on the propagation of the intermediate state into the materials will be nally discussed. The last chapter has our conclusions and perspectives for future work. Le dernier chapitre résume nos conclusions et les perspectives de développement ultérieur.
PACS. 05.40.Jc -Brownian motion. PACS. 82.70.Dd -Colloids. PACS. 67.40.Hf -Hydrodynamics in speci... more PACS. 05.40.Jc -Brownian motion. PACS. 82.70.Dd -Colloids. PACS. 67.40.Hf -Hydrodynamics in specific geometries, flow in narrow channels. Abstract. -Space-dependent diffusion of micrometer-sized particles has been directly observed using digital video microscopy. The particles were trapped between two nearly parallel walls making their confinement position dependent. Consequently, not only did we measure a diffusion coefficient which depended on the particles' position, but also report and explain a new effect: a drift of the particles' individual positions in the direction of the diffusion coefficient gradient, in the absence of any external force or concentration gradient. Brownian motion of spherical colloidal particles in the vicinity of a wall has been extensively studied, both theoretically [1-3] and experimentally In this article, we report some new experimental results concerning the Brownian motion of particles trapped between two nearly parallel walls, so that th...
Physical Review A, 2007
We study the effects of interaction between bosons and fermions in a Bose-Fermi mixtures loaded i... more We study the effects of interaction between bosons and fermions in a Bose-Fermi mixtures loaded in an optical lattice. We concentrate on the destruction of a bosonic Mott phase driven by repulsive interaction between bosons and fermions. Once the Mott phase is destroyed, the system enters a superfluid phase where the movements of bosons and fermions are correlated. We show that this phase has simultaneously correlations reminiscent of a conventional superfluid and of a pseudo-spin density wave order.
Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have... more Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have suggested that momentum dependence of the electron-phonon coupling plays an important role in their properties. Initial attempts to study Hamiltonians which either do not include or else truncate the range of Coulomb repulsion have noted that the resulting spatial non-locality of the electron-phonon interaction leads to a dominant tendency to phase separation. Here we present Quantum Monte Carlo results for such models in which we incorporate both on-site and intersite electron-electron interactions. We show that these can stabilize phases in which the density is homogeneous and determine the associated phase boundaries. As a consequence, the physics of momentum dependent electron-phonon coupling can be determined outside of the trivial phase separated regime.
Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have... more Recent studies of pairing and charge order in materials such as FeSe, SrTiO_3, and 2H-NbSe_2 have suggested that momentum dependence of the electron-phonon coupling plays an important role in their properties. Initial attempts to study Hamiltonians which either do not include or else truncate the range of Coulomb repulsion have noted that the resulting spatial non-locality of the electron-phonon interaction leads to a dominant tendency to phase separation. Here we present Quantum Monte Carlo results for such models in which we incorporate both on-site and intersite electron-electron interactions. We show that these can stabilize phases in which the density is homogeneous and determine the associated phase boundaries. As a consequence, the physics of momentum dependent electron-phonon coupling can be determined outside of the trivial phase separated regime.
Bo Xiao, F. Hébert, G. Batrouni, 3, 4, 5, 6 and R.T. Scalettar Department of Physics, University ... more Bo Xiao, F. Hébert, G. Batrouni, 3, 4, 5, 6 and R.T. Scalettar Department of Physics, University of California, Davis, CA 95616,USA Université Côte d’Azur, CNRS, INPHYNI, France MajuLab, CNRS-UCA-SU-NUS-NTU International Joint Research Unit, 117542 Singapore Centre for Quantum Technologies, National University of Singapore, 2 Science Drive 3, 117542 Singapore Department of Physics, National University of Singapore, 2 Science Drive 3, 117542 Singapore Beijing Computational Science Research Center, Beijing 100193, China (Dated: April 2, 2019)
AIP Conference Proceedings, 2003
We study the ground state properties of the 1-D boson and fermion Hubbard models in harmonic trap... more We study the ground state properties of the 1-D boson and fermion Hubbard models in harmonic traps with an underlying lattice. The physics of these systems is found to be fundamentally different from the homogeneous case. Global quantities lose their meaning and Mott domains appear for a continuous range of incommensurate fillings. A local order parameter is defined to characterize
Ultracold Gases and Quantum Information, 2011
Physical Review Letters, 2005
Physical Review Letters, 1994
Physical Review Letters, 2012
The nature of magnetic order and transport properties near surfaces is a topic of great current i... more The nature of magnetic order and transport properties near surfaces is a topic of great current interest. Here we model metal-insulator interfaces with a multi-layer system governed by a tightbinding Hamiltonian in which the interaction is non-zero on one set of adjacent planes and zero on another. As the interface hybridization is tuned, magnetic and metallic properties undergo an evolution that reflects the competition between anti-ferromagnetism and (Kondo) singlet formation in a scenario similar to that occurring in heavy-fermion materials. For a few-layer system at intermediate hybridization, a Kondo insulating phase results where magnetic order and conductivity are suppressed in all layers. As more insulating layers are added, magnetic order is restored in all correlated layers except that at the interface. Residual signs of Kondo physics are however evident in the bulk as a substantial reduction of the order parameter in the 2-3 layers immediately adjacent to the interfacial one. We find no signature of long range magnetic order in the metallic layers.
Physical Review E, 2002
We investigate numerically the failure process when two elastic media, one hard and one soft that... more We investigate numerically the failure process when two elastic media, one hard and one soft that have been glued together thus forming a common interface, are pulled apart. We present three main results: (1) The area distribution of simultaneously failing glue (bursts) follows a power law consistent with the theoretically expected exponent 2.5, (2) the maximum load and displacement before catastrophic failure scale as L 2 and L 0 respectively, where L is the linear size of the system, and (3) the area distribution of failed glue regions (clusters) is a power law with exponent −1.6 when the system fails catstrophically.
Physical Review B, 2005
We present Quantum Monte Carlo simulations of the soft-core bosonic Hubbard model with a ring exc... more We present Quantum Monte Carlo simulations of the soft-core bosonic Hubbard model with a ring exchange term K. For values of K which exceed roughly half the on-site repulsion U , the density is a non-monotonic function of the chemical potential, indicating that the system has a tendency to phase separate. This behavior is confirmed by an examination of the density-density structure factor at small momenta and real space images of the boson configurations. Adding a near-neighbor repulsion can compete with phase separation, but still does not give rise to a stable normal Bose liquid.
Physical Review B, 2009
We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantu... more We study the attractive fermionic Hubbard model on a honeycomb lattice using determinantal quantum Monte Carlo simulations. By increasing the interaction strength U (relative to the hopping parameter t) at half-filling and zero temperature, the system undergoes a quantum phase transition at 5.0 < Uc/t < 5.1 from a semi-metal to a phase displaying simultaneously superfluid behavior and density order. Doping away from half-filling, and increasing the interaction strength at finite but low temperature T , the system always appears to be a superfluid exhibiting a crossover between a BCS and a molecular regime. These different regimes are analyzed by studying the spectral function. The formation of pairs and the emergence of phase coherence throughout the sample are studied as U is increased and T is lowered.
Physical Review B, 2012
The low-temperature properties of the two-dimensional attractive Hubbard model are strongly influ... more The low-temperature properties of the two-dimensional attractive Hubbard model are strongly influenced by the fermion density. Away from half-filling, there is a finite-temperature transition to a phase with s-wave pairing order. However, Tc is suppressed to zero at half-filling, where long-range charge-density-wave order also appears, degenerate with superconductivity. This paper presents Determinant Quantum Monte Carlo simulations of the attractive Hubbard model in the presence of a confining potential Vtrap which makes the fermion density ρ inhomogeneous across the lattice. Pair correlations are shown to be large at low temperatures in regions of the trapped system with incommensurate filling, and to exhibit a minimum as the local density ρ(i) passes through one fermion per site. In this ring of ρ(i) = 1, charge order is enhanced. A comparison is made between treating Vtrap within the local-density approximation (LDA) and in an ab initio manner. It is argued that certain sharp features of the LDA result at integer filling do not survive the proximity of doped sites. The critical temperature of confined systems of fixed characteristic density is estimated.
Nuclear Physics B, 1982
ABSTRACT We extend Halpern's field-strength formulation and dual potentials (for continuu... more ABSTRACT We extend Halpern's field-strength formulation and dual potentials (for continuum gauge theories) to abelian and non-abelian lattice gauge theories. New results include: (i) plaquette formulation of all lattice gauge theories, (ii) the strong coupling expansion is seen as (a) a perturbation in dual links or (b) a gradual restoration of the lattice Bianchi identity. To leading order in the strong coupling expansion the lattice Bianchi identity is completely ignored. Geometrical interpretation of the lattice Bianchi identity is presented along with a discussion of the “abelianization” of the non-abelian identity and its connection with gauge-invariant variables. For abelian theories we also show that the dual potential is Fourier conjugate to the Bianchi identity and that the Coulomb gas representation of these theories is easily obtained in this formulation.
Journal of the Physical Society of Japan, 2005
We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, fo... more We present results from quantum Monte Carlo simulations of trapped bosons in optical lattices, focusing on the crossover from a gas of softcore bosons to a Tonks-Girardeau gas in a one-dimensional optical lattice. We find that depending on the quantity being measured, the behavior found in the Tonks-Girardeau regime is observed already at relatively small values of the interaction strength. A finite critical value for entering the Tonks-Girardeau regime does not exist. Furthermore, we discuss the computational efficiency of two quantum Monte Carlo methods to simulate large scale trapped bosonic systems: directed loops in stochastic series expansions and the worm algorithm.