505 research outputs found
Low energy quantum regimes of 1D dipolar Hubbard model with correlated hopping
We apply the bosonization technique to derive the phase diagram of a balanced
unit density two-component dipolar Fermi gas in a one dimensional lattice
geometry. The considered interaction processes are of the usual contact and
dipolar long-range density-density type together with peculiar correlated
hopping terms which can be generated dynamically. Rigorous bounds for the
transition lines are obtained in the weak coupling regime. In addition to the
standard bosonization description, we derive the low energy phase diagram
taking place when part of the interaction is embodied non-perturbatively in the
single component Hamiltonians. In this case the Luttinger liquid regime is
shown to become unstable with respect to the opening of further gapped phases,
among which insulating bond ordered wave and Haldane phases, the latter with
degenerate edge modes.Comment: 6 pages, 1 figur
Homogeneous and domain-wall topological Haldane conductors with dressed Rydberg atoms
The interplay between antiferromagnetic interaction and hole motion is capable of inducing conducting Haldane phases with topological features described by a finite nonlocal string order parameter. Here we show that these states of matter are captured by the one-dimensional
t
−
J
z
model, which can be experimentally realized with dressed Rydberg atoms trapped onto a one-dimensional optical lattice. In the sector with vanishing total magnetization, exact calculations associated with the bosonization technique allow us to predict that both metallic and superconducting topological Haldane states can be achieved. With the addition of an appropriate magnetic field, the system enters a domain-wall structure with finite total magnetization. In this regime, the conducting Haldane states are confined in domains separated by regions where a fully polarized Luttinger liquid occurs. A procedure to dynamically stabilize such topological phases starting from a confined Ising state is also described
Hidden magnetism in periodically modulated one dimensional dipolar fermions
The experimental realization of time-dependent ultracold lattice systems has paved the way towards the implementation of new Hubbard-like Hamiltonians. We show that in a one-dimensional two-components lattice dipolar Fermi gas the competition between long range repulsion and correlated hopping induced by periodically modulated on-site interaction allows for the formation of hidden magnetic phases, with degenerate protected edge modes. The magnetism, characterized solely by string-like nonlocal order parameters, manifests in the charge and/or in the spin degrees of freedom. Such behavior is enlighten by employing Luttinger liquid theory and numerical methods. The range of parameters for which hidden magnetism is present can be reached by means of the currently available experimental setups and probes
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
One dimensional extended Hubbard model: two-particle bound states and resonances.
In questo lavoro di tesi è stato svolto uno studio analitico sul modello di Hubbard esteso unidimensionale al fine di osservare la presenza di eventuali risonanze che possano dare origine alla formazione di stati legati di due particelle. L'esistenza di uno stato legato stabile ha suscitato grande interesse negli ultimi anni, sia in ambito teorico che sperimentale, poichè è alla base di molti fenomeni che vengono osservati nei sistemi a molti corpi a basse temperature, come il BCS-BEC crossover. Pertanto si è ritenuto utile studiare il problema a due corpi nel modello di Hubbard esteso, che in generale non è integrabile. Il modello considerato contiene interazioni a primi e secondi vicini, in aggiunta all'interazione di contatto presente nel modello di Hubbard.
Il problema è stato indagato analiticamente attraverso il Bethe ansatz, che consente di trovare tutti gli autovalori e le autofunzioni dell'Hamiltoniana. L'ansatz di Bethe sulla funzione d'onda è stato generalizzato per poter tener conto dei termini di interazione a più lungo raggio rispetto all'interazione di contatto.
Si trova che, in questo modello, nel limite termodinamico, possono avvenire delle risonanze (o quasi-risonanze) in cui la lunghezza di scattering diverge, contrariamente a quanto avviene nel modello di Hubbard. Tale fenomeno si verifica quando il livello energetico discreto degli stati legati “tocca” la banda di scattering. Inoltre, con l'aggiunta di nuovi termini di interazione emergono nuovi stati legati. Nel caso in esame, si osservano due famiglie di stati legati, se lo spin totale delle due particelle è 1, e tre famiglie di stati legati, se lo spin totale è 0
Non-local orders in Hubbard-like low dimensional systems
This PhD thesis is devoted to explore non-local orders in low-dimensional Hubbard-like systems. This kind of systems plays a crucial role in condensed matter physics. They were originally introduced to model solid state materials and, indeed, they successfully describe many observed physical phenomena. Additionally, in last decades, their scientific interest has exponentially increased thanks to the experiments with cold atoms, which have opened the opportunity to simulate and manipulate this type of lattice models. Trapping ultracold atomic gases into an optical lattice potential provides the purest realization of Hubbard Hamiltonians. Most important, the high control on the parameters involved allows to achieve even new fascinating regimes, among them exotic phases occurring in one and two spatial dimensions. These investigations are extremely interesting, since they unveil a totally novel physics, with many potential applications. On the other hand, from the theoretical point of view, Landau developed a theory that classifies possible phases of matter according to their symmetry. These are called spontaneous symmetry breaking phases and are typically identified by a local order parameter. Nevertheless, recent researches have proven that many more phases may exist in quantum systems. These are often called non-symmetry-breaking, hidden, exotic or topological phases. Hidden phases can be revealed by non-local order parameters. Given their central task in this attractive scenario, here we undertake to provide an overview on the capability of non-local order parameters to detect fully or partly gapped quantum phases and capture their essential microscopic features. To this end, we study their behavior, both analytically and numerically, in different systems. First of all we show that they can probe a large variety of one-dimensional quantum phases, actually all of them in the kind of Hamiltonians we will consider. Then, we will use them to uncover possible new phases and, finally, we will successfully attempt a generalization to the two dimensional case. Our results supply a step forward in the comprehension of this valuable tool and its range of applicability, in addition to the information we managed to disclose about the physical systems we studied, thanks to their employment
Hidden Charge Orders in Low-Dimensional Mott Insulators
The opening of a charge gap driven by interaction is a fingerprint of the transition to a Mott insulating phase. In strongly correlated low-dimensional quantum systems, it can be associated to the ordering of hidden non-local operators. For Fermionic 1D models, in the presence of spin⁻charge separation and short-ranged interaction, a bosonization analysis proves that such operators are the parity and/or string charge operators. In fact, a finite fractional non-local parity charge order is also capable of characterizing some two-dimensional Mott insulators, in both the Fermionic and the bosonic cases. When string charge order takes place in 1D, degenerate edge modes with fractional charge appear, peculiar of a topological insulator. In this article, we review the above framework, and we test it to investigate through density-matrix-renormalization-group (DMRG) numerical analysis the robustness of both hidden orders at half-filling in the 1D Fermionic Hubbard model extended with long range density-density interaction. The preliminary results obtained at finite size including several neighbors in the case of dipolar, screened and unscreened repulsive Coulomb interactions, confirm the phase diagram of the standard extended Hubbard model. Besides the trivial Mott phase, the bond ordered and charge density wave insulating phases are also not destroyed by longer ranged interaction, and still manifest hidden non-local orders
Hidden Magnetism in Periodically Modulated One Dimensional Dipolar Fermions
info:eu-repo/semantics/publishe
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