1,978 research outputs found
Two-Step Electroweak Baryogenesis
We analyze electroweak baryogenesis during a two-step electroweak symmetry
breaking transition, wherein the baryon asymmetry is generated during the first
step and preserved during the second. Focusing on the dynamics of CP-violation
required for asymmetry generation, we discuss general considerations for
successful two-step baryogenesis. Using a concrete model realization, we
illustrate in detail the viability of this scenario and the implications for
present and future electric dipole moment (EDM) searches. We find that
CP-violation associated with a partially excluded sector may yield the observed
baryon asymmetry while evading present and future EDM constraints.Comment: 20 pages, 11 figure
High-order correlation effects in the two-dimensional Hubbard model
The electronic states of the two-dimensional Hubbard model are investigated
by means of a 4-pole approximation within the Composite Operator Method. In
addition to the conventional Hubbard operators, we consider other two operators
which come from the hierarchy of the equations of motion and carry information
regarding nearest-neighbor spin and charge configurations. By means of this
operatorial basis, we can study the physics related to the energy scale of
J=4t^2/U in addition to the one of U. Present results show relevant physical
features, well beyond those previously obtained by means of a 2-pole
approximation, such as a four-band structure with shadow bands and a
quasi-particle peak at the Fermi level. The Fermi level stays pinned to the
band flatness located at (pi,0)-point within a wide range of hole-doping (0 <=
delta <= 0.15). A comprehensive analysis of double occupancy, internal energy,
specific heat and entropy features have been also performed. All reported
results are in excellent agreement with the data of numerical simulations.Comment: 13 pages, 8 figure
Continuous Transition between Antiferromagnetic Insulator and Paramagnetic Metal in the Pyrochlore Iridate Eu2Ir2O7
Our single crystal study of the magneto-thermal and transport properties of
the pyrochlore iridate Eu2Ir2O7 reveals a continuous phase transition from a
paramagnetic metal to an antiferromagnetic insulator for a sample with
stoichiometry within ~1% resolution. The insulating phase has strong proximity
to an antiferromagnetic semimetal, which is stabilized by several % level of
the off-stoichiometry. Our observations suggest that in addition to electronic
correlation and spin-orbit coupling the magnetic order is essential for opening
the charge gap.Comment: 6 pages, 6 figure
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