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M. Ferrero

Publications and source records attributed to M. Ferrero.

52 records · Page 3Linked to original sources
arXiv2013

Impact of electronic correlations on the equation of state and transport in $ε$-Fe

We have obtained the equilibrium volumes, bulk moduli, equations of state of the ferromagnetic cubic $α$ and paramagnetic hexagonal $ε$ phases of iron in close agreement with experiment using an ab initio dynamical mean-field theory approach. The local dynamical correlations are shown to be crucial for a successful description of the ground-state properties of paramagnetic $ε$-Fe. Moreover, they enhance the effective mass of the quasiparticles and reduce their lifetimes across the $α\to ε$ transition leading to a step-wise increase of the resistivity, as observed in experiment. The calculated magnitude of the jump is significantly underestimated, which points to non-local correlations. The implications of our results for the superconductivity and non-Fermi-liquid behavior of $ε$-Fe are discussed.

cond-mat.str-el↗
arXiv2013

The Relevance of the Preparation Concept in the Interpretation of Quantum Formalism

The preparation procedure, an undefined notion in quantum theory, has not had the relevance that it deserves in the interpretation of quantum mechanical formalism. Here we utilize the concepts of identical and similar preparation procedures to show the conceptual differences and mutual interconnections between the statistical and the conventional interpretation of quantum formalism. Although the statistical understanding, and its final logical consequence, hidden variables theories (this connexion being explained in the text), have a great intuitive appeal due to its fewer ontological difficulties, both recent experimental results and some theoretical developments seem to support an epistemic alternative closer to the conventional one. Nevertheless, we must not rule out the possibility that new theorems or new explanatory principles may modify the reigning supremacy of this interpretation.

quant-ph↗
arXiv2013

Heuristic Classification of Physical Theories based on Quantum Correlations

Taking quantum formalism as a point of reference and connection, we explore the various possibilities that arise in the construction of physical theories. Analyzing the distinct physical phenomena that each of them may describe, we introduce the different types of hidden variables theories that correspond to these physical phenomena. A hierarchical classification of the offered theories, based on the degree of correlation between dichotomic observables in bipartite systems, as quantified by a Bell type inequality, is finally proposed.

quant-ph↗
arXiv2012

Electronic band structure of BaCo$_{2}$As$_2$: a fully-doped ferropnictide with reduced electronic correlations

We report an angle-resolved photoemission spectroscopy investigation of the Fermi surface and electronic band structure of BaCo$_{2}$As$_2$. Although its quasi-nesting-free Fermi surface differs drastically from that of its Fe-pnictide cousins, we show that the BaCo$_{2}$As$_2$ system can be used as an approximation to the bare unoccupied band structure of the related BaFe$_{2-x}$Co$_x$As$_2$ and Ba$_{1-x}$K$_x$Fe$_2$As$_2$ compounds. However, our experimental results, in agreement with dynamical mean field theory calculations, indicate that electronic correlations are much less important in BaCo$_{2}$As$_2$ than in the ferropnictides. Our findings suggest that this effect is due to the increased filling of the electronic 3$d$ shell in the presence of significant Hund's exchange coupling.

cond-mat.str-el↗
arXiv2012

Mott transition of fermionic mixtures with mass imbalance in optical lattices

We investigate the effect of mass imbalance in binary Fermi mixtures loaded in optical lattices. Using dynamical mean-field theory, we study the transition from a fluid to a Mott insulator driven by the repulsive interactions. For almost every value of the parameters we find that the light species with smaller bare mass is more affected by correlations than the heavy one, so that their effective masses become closer than their bare masses before a Mott transition occurs. The strength of the critical repulsion decreases monotonically as the mass imbalance grows so that the minimum is realized when one of the species is localized. The evolution of the spectral functions testifies that a continuous loss of coherence and a destruction of the Fermi liquid occur as the imbalance grows. The two species display distinct properties and experimentally-observable deviations from the behavior of a balanced Fermi mixture.

cond-mat.str-el↗
arXiv2011

A Critical Discussion About The Methodology Of Quantum Theory

It is argued that the traditional "realist" methodology of physics, according to which human concepts, laws and theories can grasp the essence of reality, is incompatible with the most fruitful interpretation of quantum formalism. The proof rests on the violation by quantum mechanics of the foundational principles of that methodology. An alternative methodology, in which the construction of sciences finishes at the level of human experience, as standard quantum theory strongly suggests, is then conjectured.

quant-ph↗
arXiv2010

Interplane charge dynamics in a valence-bond dynamical mean-field theory of cuprate superconductors

We present calculations of the interplane charge dynamics in the normal state of cuprate superconductors within the valence-bond dynamical mean-field theory. We show that by varying the hole doping, the c-axis optical conductivity and resistivity dramatically change character, going from metallic-like at large doping to insulating-like at low-doping. We establish a clear connection between the behavior of the c-axis optical and transport properties and the destruction of coherent quasiparticles as the pseudogap opens in the antinodal region of the Brillouin zone at low doping. We show that our results are in good agreement with spectroscopic and optical experiments.

cond-mat.str-el↗
arXiv2010

A cone approach to the quantum separability problem

Exploiting the cone structure of the set of unnormalized mixed quantum states, we offer an approach to detect separability independently of the dimensions of the subsystems. We show that any mixed quantum state can be decomposed as $ρ=(1-λ)C_ρ+λE_ρ$, where $C_ρ$ is a separable matrix whose rank equals that of $ρ$ and the rank of $E_ρ$ is strictly lower than that of $ρ$. With the simple choice $C_ρ=M_{1}\otimes M_{2}$ we have a necessary condition of separability in terms of $λ$, which is also sufficient if the rank of $E_ρ$ equals 1. We give a first extension of this result to detect genuine entanglement in multipartite states and show a natural connection between the multipartite separability problem and the classification of pure states under stochastic local operations and classical communication (SLOCC). We argue that this approach is not exhausted with the first simple choices included herein.

quant-ph↗
arXiv2009

Pseudogap opening and formation of Fermi arcs as an orbital-selective Mott transition in momentum space

We present an approach to the normal state of cuprate superconductors which is based on a minimal cluster extension of dynamical mean-field theory. Our approach is based on an effective two-impurity model embedded in a self-consistent bath. The two degrees of freedom of this effective model can be associated to the nodal and antinodal regions of momentum space. We find a metal-insulator transition which is selective in momentum space: At low doping quasiparticles are destroyed in the antinodal region, while they remain protected in the nodal region, leading to the formation of apparent Fermi arcs. We compare our results to tunneling and angular-resolved photoemission experiments on cuprates. At very low energy, a simple description of this transition can be given using rotationally invariant slave bosons.

cond-mat.str-el↗
arXiv2009

Trapping and cooling fermionic atoms into the Mott and Néel states

We perform a theoretical study of a fermionic gas with two hyperfine states confined to an optical lattice. We derive a generic state diagram as a function of interaction strength, particle number, and confining potential. We discuss the central density, the double occupancy and their derivatives as probes for the Mott state, connecting our findings to the recent experiment of Jördens et al. Using entropic arguments we compare two different strategies to reach the antiferromagnetic state in the presence of a trapping potential.

cond-mat.str-el↗
arXiv2008

Valence-Bond Dynamical Mean-Field Theory of Doped Mott Insulators with Nodal/Antinodal Differentiation

We introduce a valence-bond dynamical mean-field theory of doped Mott insulators. It is based on a minimal cluster of two orbitals, each associated with a different region of momentum space and hybridized to a self-consistent bath. The low-doping regime is characterized by singlet formation and the suppression of quasiparticles in the antinodal regions, leading to the formation of Fermi arcs. This is described in terms of an orbital-selective transition in reciprocal space. The calculated tunneling and photoemission spectra are consistent with the phenomenology of the normal state of cuprates. We derive a low-energy description of these effects using a generalization of the slave-boson method.

cond-mat.str-el↗
arXiv2008

Quantum Mechanics, is it magic?

We show that quantum mechanics is the first theory in human history that violates the basic a priori principles that have shaped human thought since immemorial times. Therefore although it is more contrary to magic than any body of knowledge could be, what could be called its magic precisely resides in this violation.

physics.hist-ph↗
arXiv2007

Strong Correlations in a nutshell

We present the phase diagram of clusters made of two, three and four coupled Anderson impurities. All three clusters share qualitatively similar phase diagrams that include Kondo screened and unscreened regimes separated by almost critical crossover regions reflecting the proximity to barely avoided critical points. This suggests the emergence of universal paradigms that apply to clusters of arbitrary size. We discuss how these crossover regions of the impurity models might affect the approach to the Mott transition within a cluster extension of dynamical mean field theory.

cond-mat.str-el↗
arXiv2005

Another dual formulation of the separability problem

We show how the separability problem is dual to that of decomposing any given matrix into a conic combination of rank-one partial isometries, thus offering a duality approach different to the positive maps characterization problem. Several inmediate consequences are analyzed: (i) a sufficient criterion for separability for bipartite quantum systems, (ii) a complete solution to the separability problem for pure states also of bipartite systems independent of the classical Schmidt decomposition method and (iii) a natural generalization of these results to multipartite systems.

quant-ph↗
arXiv2005

On nonlinear evolution and supraluminal communication between finite quantum systems

We revise the 'no-signaling' condition for the supraluminal communication between two spatially separated finite quantum systems of arbitrary dimensions, thus generalizing a similar preceding approach for two-qubits: non-linear evolution does not necessarily imply the possibility of supraluminal communication between any sort of finite quantum systems.

quant-ph↗