91 citations · 235 across the 8 of their papers we have counts for
8 papers
Charge and Spin Quantum Fluids Generated by Many-Electron Interactions
J. M. P. Carmelo, J. M. Roman, K. Penc
In this paper we describe the electrons of the 1D Hubbard model by a fluid of unpaired rotated electrons and a fluid of zero-spin rotated-electron pairs. The rotated electrons are…
The elementary excitations of the BCS model in the canonical ensemble
G. Sierra, J. M. Roman, J. Dukelsky
We summarize previous works on the exact ground state and the elementary excitations of the exactly solvable BCS model in the canonical ensemble. The BCS model is solved by Richard…
What are the elementary excitations of the BCS model in the canonical ensemble?
J. M. Roman, G. Sierra, J. Dukelsky
We have found the elementary excitations of the exactly solvable BCS model for a fixed number of particles. These turn out to have a peculiar dispersion relation, some of them with…
Large N limit of the exactly solvable BCS model: analytics versus numerics
J. M. Roman, G. Sierra, J. Dukelsky
We have studied the numerical solutions of Richardson equations of the BCS model in the limit of large number of energy levels at half-filling, and compare them with the analytic r…
Spin Waves in Canted Phases: An Application to Doped Manganites
J. M. Roman, J. Soto
We present the effective lagrangian for low energy and momentum spin waves in canted phases at next to leading order in the derivative expansion. The symmetry breaking pattern SU(2…
Continuum Double Exchange Model
J. M. Roman, J. Soto
We present a continuum model for doped manganites which consist of two species of quantum spin 1/2 fermions interacting with classical spin fields. The phase structure at zero temp…
The Matrix Product Approach to Quantum Spin Ladders
J. M. Roman, G. Sierra, J. Dukelsky +1
We present a manifestly rotational invariant formulation of the matrix product method valid for spin chains and ladders. We apply it to 2 legged spin ladders with spins 1/2, 1 and…
Spin wave mediated non-reciprocal effects in antiferromagnets
J. M. Roman, J. Soto
By using an effective field theory for the electromagnetic interaction of spin waves, we show that, in certain antiferromagnets, the latter induce non-reciprocal effects in the mic…