103 research outputs found
Dicyclic Horizontal Symmetry and Supersymmetric Grand Unification
It is shown how to use as horizontal symmetry the dicyclic group in a supersymmetric unification where
one acts on the first and second families, in a horizontal doublet, and
the other acts on the third. This can lead to acceptable quark masses and
mixings, with an economic choice of matter supermultiplets, and charged lepton
masses can be accommodated.Comment: 10 pages, LaTe
Imaging phonon-mediated hydrodynamic flow in WTe2
In the presence of interactions, electrons in condensed-matter systems can
behave hydrodynamically, exhibiting phenomena associated with classical fluids,
such as vortices and Poiseuille flow. In most conductors, electron-electron
interactions are minimized by screening effects, hindering the search for
hydrodynamic materials; however, recently, a class of semimetals has been
reported to exhibit prominent interactions. Here we study the current flow in
the layered semimetal tungsten ditelluride by imaging the local magnetic field
using a nitrogen-vacancy defect in a diamond. We image the spatial current
profile within three-dimensional tungsten ditelluride and find that it exhibits
non-uniform current density, indicating hydrodynamic flow. Our
temperature-resolve current profile measurements reveal a non-monotonic
temperature dependence, with the strongest hydrodynamic effects at
approximately 20 K. We also report ab initio calculations showing that
electron-electron interactions are not explained by the Coulomb interaction
alone, but are predominantly mediated by phonons. This provides a promising
avenue in the search for hydrodynamic flow and prominent electron interactions
in high-carrier-density materials.Comment: 11 pages, 4 figures + supplementary materia
A Supersymmetric Theory of Flavor and R Parity
We construct a renormalizable, supersymmetric theory of flavor and parity
based on the discrete flavor group . The model can account for all the
masses and mixing angles of the Standard Model, while maintaining sufficient
squark degeneracy to circumvent the supersymmetric flavor problem. By starting
with a simpler set of flavor symmetry breaking fields than we have suggested
previously, we construct an economical Froggatt-Nielsen sector that generates
the desired elements of the fermion Yukawa matrices. With the particle content
above the flavor scale completely specified, we show that all renormalizable
-parity-violating interactions involving the ordinary matter fields are
forbidden by the flavor symmetry. Thus, parity arises as an accidental
symmetry in our model. Planck-suppressed operators that violate parity, if
present, can be rendered harmless by taking the flavor scale to be GeV.Comment: 28 pp. LaTeX, 1 Postscript Figur
Fermion Electric Dipole Moments in Supersymmetric Models with R-parity Violation
We analyze the electron and neutron electric dipole moments induced by
R-parity violating interactions in supersymmetric models. It is pointed out
that dominant contributions can come from one-loop diagrams involving both the
bilinear and trilinear R-parity odd couplings, leading to somewhat severe
constraints on the products of those couplings.Comment: Revtex, 19pp, four figures in axodraw.st
Electron quantum metamaterials in van der Waals heterostructures
In recent decades, scientists have developed the means to engineer synthetic
periodic arrays with feature sizes below the wavelength of light. When such
features are appropriately structured, electromagnetic radiation can be
manipulated in unusual ways, resulting in optical metamaterials whose function
is directly controlled through nanoscale structure. Nature, too, has adopted
such techniques -- for example in the unique coloring of butterfly wings -- to
manipulate photons as they propagate through nanoscale periodic assemblies. In
this Perspective, we highlight the intriguing potential of designer
sub-electron wavelength (as well as wavelength-scale) structuring of electronic
matter, which affords a new range of synthetic quantum metamaterials with
unconventional responses. Driven by experimental developments in stacking
atomically layered heterostructures -- e.g., mechanical pick-up/transfer
assembly -- atomic scale registrations and structures can be readily tuned over
distances smaller than characteristic electronic length-scales (such as
electron wavelength, screening length, and electron mean free path). Yet
electronic metamaterials promise far richer categories of behavior than those
found in conventional optical metamaterial technologies. This is because unlike
photons that scarcely interact with each other, electrons in subwavelength
structured metamaterials are charged, and strongly interact. As a result, an
enormous variety of emergent phenomena can be expected, and radically new
classes of interacting quantum metamaterials designed
Supersymmetric Froggatt-Nielsen Models with Baryon- and Lepton-Number Violation
We systematically investigate the embedding of U(1)_X Froggatt-Nielsen models
in (four-dimensional) local supersymmetry. We restrict ourselves to models with
a single flavon field. We do not impose a discrete symmetry by hand, e.g.
R-parity, baryon-parity or lepton-parity. Thus we determine the order of
magnitude of the baryon- and/or lepton violating coupling constants through the
Froggatt-Nielsen mechanism. We then scrutinize whether the predicted coupling
constants are in accord with weak or GUT scale constraints. Many models turn
out to be incompatible.Comment: Final version, references added, minor corrections; LaTeX, 46 page
Predictions from an Anomalous U(1) Model of Yukawa Hierarchies
We present a supersymmetric standard model with three gauged Abelian
symmetries, of a type commonly found in superstrings. One is anomalous, the
other two are family symmetries. It has a vacuum in which only these
symmetries are broken by stringy effects. It reproduces all observed quark and
charged lepton Yukawa hierarchies, and the value of the Weinberg angle. It
predicts three massive neutrinos, with mixing that can explain both the small
angle MSW effect, and the atmospheric neutrino anomaly. The Cabibbo angle is
expressed in terms of the gauge couplings at unification. It conserves
R-parity, and proton decay is close to experimental bounds.Comment: 26 page
The magnetic genome of two-dimensional van der Waals materials
Magnetism in two-dimensional (2D) van der Waals (vdW) materials has recently emerged as one of the most promising areas in condensed matter research, with many exciting emerging properties and significant potential for applications ranging from topological magnonics to low-power spintronics, quantum computing, and optical communications. In the brief time after their discovery, 2D magnets have blossomed into a rich area for investigation, where fundamental concepts in magnetism are challenged by the behavior of spins that can develop at the single layer limit. However, much effort is still needed in multiple fronts before 2D magnets can be routinely used for practical implementations. In this comprehensive review, prominent authors with expertise in complementary fields of 2D magnetism (i.e., synthesis, device engineering, magneto-optics, imaging, transport, mechanics, spin excitations, and theory and simulations) have joined together to provide a genome of current knowledge and a guideline for future developments in 2D magnetic materials research
Supersymmetry without R-Parity and without Lepton Number
We investigate Supersymmetric models where neither R parity nor lepton number
is imposed. Neutrino masses can be kept highly suppressed compared to the
electroweak scale if the -terms in the superpotential are aligned with the
SUSY-breaking bilinear -terms. This situation arises naturally in the
framework of horizontal symmetries. The same symmetries suppress the trilinear
R parity violating terms in the superpotential to an acceptable level.Comment: 18 pages, harvma
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