B. Bernu
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View article: Derivation of free energy, entropy and specific heat for planar Ising models: Application to Archimedean lattices and their duals
Derivation of free energy, entropy and specific heat for planar Ising models: Application to Archimedean lattices and their duals Open
The 2d ferromagnetic Ising model was solved by Onsager on the square lattice in 1944, and an explicit expression of the free energy density f is presently available for some other planar lattices. But determining exactly the critical tem…
View article: Derivation of the free energy, entropy and specific heat for planar Ising models: Application to Archimedean lattices and their duals
Derivation of the free energy, entropy and specific heat for planar Ising models: Application to Archimedean lattices and their duals Open
The 2d ferromagnetic Ising model was solved by Onsager on the square lattice in 1944, and an explicit expression of the free energy density $f$ is presently available for some other planar lattices. But an exact derivation of the critical …
View article: High temperature series expansions of S = 1/2 Heisenberg spin models: Algorithm to include the magnetic field with optimized complexity
High temperature series expansions of S = 1/2 Heisenberg spin models: Algorithm to include the magnetic field with optimized complexity Open
This work presents an algorithm for calculating high temperature series expansions (HTSE) of Heisenberg spin models with spin S=1/2 in the thermodynamic limit. This algorithm accounts for the presence of a magnetic field. The paper …
View article: High temperature series expansions of S = 1/2 Heisenberg spin models: algorithm to include the magnetic field with optimized complexity
High temperature series expansions of S = 1/2 Heisenberg spin models: algorithm to include the magnetic field with optimized complexity Open
This work presents an algorithm for calculating high temperature series expansions (HTSE) of Heisenberg spin models with spin $S=1/2$ in the thermodynamic limit. This algorithm accounts for the presence of a magnetic field. The paper begin…
View article: Ground-state and thermodynamic properties of the spin-$\frac{1}{2}$ Heisenberg model on the anisotropic triangular lattice
Ground-state and thermodynamic properties of the spin-$\frac{1}{2}$ Heisenberg model on the anisotropic triangular lattice Open
The spin- \frac12 triangular lattice antiferromagnetic Heisenberg model has been for a long time the prototypical model of magnetic frustration. However, only very recently this model has been proposed to be realized in the Ba _8 Co…
View article: Specific Heat of the Kagome Antiferromagnet Herbertsmithite in High Magnetic Fields
Specific Heat of the Kagome Antiferromagnet Herbertsmithite in High Magnetic Fields Open
Measuring the specific heat of herbertsmithite single crystals in high\nmagnetic fields (up to $34$ T) allows us to isolate the low-temperature kagome\ncontribution while shifting away extrinsic Schottky-like contributions. The\nkagome con…
View article: Report on 2112.08128v1
Report on 2112.08128v1 Open
The spin-1 2 triangular lattice antiferromagnetic Heisenberg model has been for a long time the prototypical model of magnetic frustration.However, only very recently this model has been proposed to be realized in the Ba 8 CoNb 6 O 24 comp…
View article: Report on 2112.08128v1
Report on 2112.08128v1 Open
The spin-1 2 triangular lattice antiferromagnetic Heisenberg model has been for a long time the prototypical model of magnetic frustration.However, only very recently this model has been proposed to be realized in the Ba 8 CoNb 6 O 24 comp…
View article: Logarithmic divergent specific heat from high-temperature series expansions: Application to the two-dimensional XXZ Heisenberg model
Logarithmic divergent specific heat from high-temperature series expansions: Application to the two-dimensional XXZ Heisenberg model Open
We present an interpolation method for the specific heat $c_v(T)$, when there\nis a phase transition with a logarithmic singularity in $c_v$ at a critical\ntemperature $T=T_c$. The method uses the fact that $c_v$ is constrained both by\nit…
View article: Effect of perturbations on the kagome $S=1/2$ antiferromagnet at all temperatures
Effect of perturbations on the kagome $S=1/2$ antiferromagnet at all temperatures Open
The ground state of the $S=1/2$ kagome Heisenberg antiferromagnet is now recognized as a spin liquid, but its precise nature remains unsettled, even if more and more clues point towards a gapless spin liquid. We use high temperature series…
View article: Fixed-phase approximation and Diffusion Quantum Monte Carlo
Fixed-phase approximation and Diffusion Quantum Monte Carlo Open
We present a simple approach to the fixed phase method in Quantum Monte Carlo. This applies to electrons in molecules and electron gas and is straightforwardly extended to the Schrödinger equation with magnetic field.
View article: Periodic ground states of the electron gas in two and three dimensions
Periodic ground states of the electron gas in two and three dimensions Open
In this paper, we review the possibility of periodic ground states of the two‐ and three‐dimensional electron gas at high and intermediate densities. At the Hartree–Fock level, we obtain explicit solutions at all densities having lower ene…
View article: Chiral Spin Liquid on a Kagome Antiferromagnet Induced by the Dzyaloshinskii-Moriya Interaction
Chiral Spin Liquid on a Kagome Antiferromagnet Induced by the Dzyaloshinskii-Moriya Interaction Open
The quantum spin liquid material herbertsmithite is described by an antiferromagnetic Heisenberg model on the kagome lattice with a non-negligible Dzyaloshinskii-Moriya interaction (DMI). A well-established phase transition to the q=0 long…
View article: Nature of the Spin Liquid Ground State in a Breathing Kagome Compound Studied by NMR and Series Expansion
Nature of the Spin Liquid Ground State in a Breathing Kagome Compound Studied by NMR and Series Expansion Open
In the vanadium oxyfluoride compound (NH_{4})_{2}[C_{7}H_{14}N][V_{7}O_{6}F_{18}] (DQVOF), the V^{4+} (3d^{1}, S=1/2) ions realize a unique, highly frustrated breathing kagome lattice composed of alternately sized, corner-sharing equilater…
View article: Confidence and efficiency scaling in variational quantum Monte Carlo calculations
Confidence and efficiency scaling in variational quantum Monte Carlo calculations Open
Based on the central limit theorem, we discuss the problem of evaluation of the statistical error of Monte Carlo calculations using a time-discretized diffusion process. We present a robust and practical method to determine the effective v…
View article: Upper bounds of spin-density wave energies in the homogeneous electron gas
Upper bounds of spin-density wave energies in the homogeneous electron gas Open
Studying the jellium model in the Hartree-Fock approximation, Overhauser has shown that spin density waves (SDW) can lower the energy of the Fermi gas, but it is still unknown if these SDW are actually relevant for the phase diagram. In th…
View article: Gapless chiral spin liquid in a kagome Heisenberg model
Gapless chiral spin liquid in a kagome Heisenberg model Open
Motivated by recent experiments on the Heisenberg S=1/2 quantum spin liquid\ncandidate material kapellasite, we classify all possible chiral (time-reversal\nsymmetry breaking) spin liquids with fermionic spinons on the kagome lattice.\nWe …
View article: Spin Susceptibility of Quantum Magnets from High to Low Temperatures
Spin Susceptibility of Quantum Magnets from High to Low Temperatures Open
We explain how and why all thermodynamic properties of spin systems can be computed in one and two dimensions in the whole range of temperatures overcoming the divergence towards zero temperature of the standard high-temperature series exp…