8 research outputs found
Thermodynamic properties of the Dicke model in the strong-coupling regime
We discuss the problem of a N two-level systems interacting with a single
radiation mode in the strong-coupling regime. The thermodynamic properties of
Dicke model are analyzed developing a perturbative expansion of the partition
function in the high-temperature limit and we use this method to investigate
the connections between the Dicke and the collective one-dimensional Ising
modelComment: 7 pages, accepted for publication in EPJ
Perturbative study of the Kitaev model with spontaneous time-reversal symmetry breaking
We analyze the Kitaev model on the triangle-honeycomb lattice whose ground
state has recently been shown to be a chiral spin liquid. We consider two
perturbative expansions: the isolated-dimer limit containing Abelian anyons and
the isolated-triangle limit. In the former case, we derive the low-energy
effective theory and discuss the role played by multi-plaquette interactions.
In this phase, we also compute the spin-spin correlation functions for any
vortex configuration. In the isolated-triangle limit, we show that the
effective theory is, at lowest nontrivial order, the Kitaev honeycomb model at
the isotropic point. We also compute the next-order correction which opens a
gap and yields non-Abelian anyons.Comment: 7 pages, 4 figures, published versio
Entanglement sharing in Jahn-Teller model in the presence of a magnetic field
We discuss the ground state entanglement of the
Jahn-Teller model in the presence of a strong transverse magnetic field as a
function of the vibronic coupling strength. A complete characterization is
given of the phenomenon of entanglement sharing in a system composed by a qubit
coupled to two bosonic modes. Using the residual -tangle, we find that
three-partite entanglement is significantly present in the system in the
parameter region near the bifurcation point of the corresponding classical
model
Entanglement of a qubit coupled to a resonator in the adiabatic regime
We discuss the ground state entanglement of a bi-partite system, composed by
a qubit strongly interacting with an oscillator mode, as a function of the
coupling strenght, the transition frequency and the level asymmetry of the
qubit. This is done in the adiabatic regime in which the time evolution of the
qubit is much faster than the oscillator one. Within the adiabatic
approximation, we obtain a complete characterization of the ground state
properties of the system and of its entanglement content.Comment: 6 pages, 7 figure
Nuclear halo and the coherent nuclear interaction
The unusual structure of Li11, the first halo nucleus found, is analyzed by
the Preparata model of nuclear structure. By applying Coherent Nucleus Theory,
we obtain an interaction potential for the halo-neutrons that rightly
reproduces the fundamental state of the system.Comment: 9 pages Submitted to International Journal of Modern Physics E
(IJMPE
Emergent Insulator-Metal Transition with Tunable Optical and Electrical Gap in Thin Films of a Molecular Conducting Composite
Composites exhibit unique synergistic properties emerging when components with different properties are combined. The tuning of the energy bandgap in the electronic structure of the material allows designing tailor-made systems with desirable mechanical, electrical, optical, and/or thermal properties. Here, we study an emergent insulator-metal transition at room temperature in bilayered (BL) thin-films comprised of polycarbonate/molecular-metal composites. Temperature-dependent resistance measurements allow monitoring of the electrical bandgap, which is in agreement with the optical bandgap extracted by optical absorption spectroscopy. The semiconductor-like properties of BL films, made with bis(ethylenedithio)-tetrathiafulvalene (BEDT-TTF or ET) α-ET2I3 (nano)microcrystals as two-dimensional molecular conductor on one side and insulator polycarbonate as a second ingredient, are attributed to an emergent phenomenon equivalent to the transition from an insulator to a metal. This made it possible to obtain semiconducting BL films with tunable electrical/optical bandgaps ranging from 0 to 2.9 eV. A remarkable aspect is the similarity close to room temperature of the thermal and mechanical properties of both composite components, making these materials ideal candidates to fabricate flexible and soft sensors for stress, pressure, and temperature aiming at applications in wearable human health care and bioelectronics.This work was funded by the Spanish Ministry with Project GENESIS PID2019-111682RB-I00 and the Generalitat de Catalunya (Grant 2017-SGR-918). R.P. acknowledges support from the RamĂłn y Cajal Fellowship (Ref. RyC2019-028474-I). J.L. is enrolled in the UAB Materials Science Ph.D. program and acknowledges his Chinese Council Ph.D. fellowship. R.L.Z. and N.A.-A. thank the European Research Council (ERC) under the European Unionâs Horizon 2020 R&D Programme (Grant ERC-724981). We thank Dr. Tommaso Salzillo and Dr. Roxana Vlad for fruitful discussions. All the authors acknowledge the financial support through the âSevero Ochoaâ program for Centers of Excellence in R&D (Grant CEX2019-000917-S).With funding from the Spanish government through the âSevero Ochoa Centre of Excellenceâ accreditation (CEX2019-000917-S).Peer reviewe