22,797 research outputs found
Statistical distribution of quantum correlation induced by multiple scattering in the disordered medium
For the quantum correlations between scattered modes in the disordered media,
the previous works focus mainly on the cases where the inputs are
non-superposed states, for instance, products of Fock states [Phys. Rev. Letts.
105 (2010) 090501]. A natural question that arises is how the superpositions
affect the quantum correlations. Following this trail, the comparison between
superpositions and products of Fock states is performed. It is found an
interesting phenomenon that for the superposition and the corresponding product
of Fock state (non-Gaussian states), their averaged quantum correlations are
nearly same, whereas the distributions of their quantum correlations might be
different. Therefore, superpositions may affect the distributions of the
quantum correlations. In addition, to examine how the Gaussian states affect
the quantum correlations, we compare the typical Gaussian states with the
non-Gaussian states (superpositions and products of Fock states). It is
discovered that the non-Gaussian-state input could result in the quantum
correlation that is either positive or negative, depending on the number of the
input modes and the number of the photons in each mode, whereas the
Gaussian-state input always leads to the non-negative quantum correlation.
Besides, it is demonstrated that with the increase of the disorder strength,
the mean strength of the quantum correlation increases for multi-mode-state
inputs (except for multi-mode-coherent-state inputs). These results may be
useful to control and adjust the quantum properties of scattered modes after
the quantized lights propagating through the disordered medium.Comment: 17 pages, 9 figure
Anomalies of weight-based coherence measure and mixed maximally coherent states
As an analogy of best separable approximation (BSA) in the framework of
entanglement theory, here we concentrate on the notion of best incoherent
approximation, with application to characterizing and quantifying quantum
coherence. From both analytical and numerical perspectives, we have
demonstrated that the weight-based coherence measure displays some unusual
properties, in sharp contrast to other popular coherence quantifiers. First, by
deriving a closed formula for qubit states, we have showed the weight-based
coherence measure exhibits a rich (geometrical) structure even in this simplest
case. Second, we have identified the existence of mixed maximally coherent
states (MMCS) with respect to this coherence measure and discussed the
characteristic feature of MMCS in high-dimensional Hilbert spaces. Especially,
we present several important families of MMCS by gaining insights from the
numerical simulations. Moreover, it is pointed out that some considerations in
this work can be generalized to general convex resource theories and a
numerical method of improving the computational efficiency for finding the BSA
is also discussed.Comment: 9 pages, 4 figure
Stabilization and modulation of the topological magnetic phase with a -vortex lattice in the Kitaev-Heisenberg honeycomb model: The key role of the third-nearest-neighbor interaction
The topologically nontrivial magnetic phase with a -vortex (ZV)
lattice is investigated by simulation in the Kitaev-Heisenberg honeycomb model
expanded by considering the second- and third-nearest-neighbor Heisenberg
interactions ( and ). On the parameter region of the ZV
phase, a gradual modulation of vortex density is observed, together with a
transition from single-ZV to triple-ZV state driven by the variation of
frustration. Additionally, vortices are arranged in different manners on
the whole honeycomb structure for these two types of ZV states. Moreover,
topologically equivalent states are revealed to exist in single-ZV dominant
and triple-ZV dominant styles on different parameter points, which can be
controlled to switch between each other without energy consumption. It is worth
noting that plays a key role in expanding the ZV phase, and also
in stabilizing the single-ZV state.Comment: 14 pages, 6 figure
The equivalence of two discretenesses of triangulated categories
Given an ST-triple one can associate a
co--structure on and a -structure on . It is
shown that the discreteness of with respect to the
co--structure is equivalent to the discreteness of with
respect to the -structure. As a special case, the discreteness of
in the sense of Vossieck is equivalent to the
discreteness of in a dual sense, where is a
finite-dimensional algebra.Comment: 17 page
The Symbiotic Contact Process
We consider a contact process on with two species that interact in a
symbiotic manner. Each site can either be vacant or occupied by individuals of
species and/or . Multiple occupancy by the same species at a single site
is prohibited. The name symbiotic comes from the fact that if only one species
is present at a site then that particle dies with rate 1 but if both species
are present then the death rate is reduced to for each particle at
that site. We show the critical birth rate for weak survival
is of order as . Mean-field calculations predict that
when there is a discontinuous transition as is varied. In
contrast, we show that, in any dimension, the phase transition is continuous.
To be fair to physicists the paper that introduced the model, the authors say
that the symbiotic contact process is in the directed percolation universality
class and hence has a continuous transition. However, a 2018 paper asserts that
the transition is discontinuous above the upper critical dimension, which is 4
for oriented percolation.Comment: 21 pages, 3 figure
Pyrochlore U(1) spin liquid of mixed symmetry enrichments in magnetic fields
We point out the experimental relevance and the detection scheme of symmetry
enriched U(1) quantum spin liquids (QSLs) outside the perturbative spin-ice
regime. Recent experiments on Ce-based pyrochlore QSL materials suggest that
the candidate QSL may not be proximate to the well-known spin ice regime, and
thus differs fundamentally from other pyrochlore QSL materials. We consider the
possibility of the -flux U(1) QSL favored by frustrated transverse
exchange interactions rather than the usual quantum spin ice. It was previously
suggested that both dipolar U(1) QSL and octupolar U(1) QSL can be realized for
the generic spin model for the dipole-octupole doublets of the Ce local
moments on the pyrochlore magnets CeSnO and CeZrO. We
explain and predict the experimental signatures especially the magnetic field
response of the octupolar -flux U(1) QSL. Fundamentally, this remarkable
state is a mixture of symmetry enrichments from point group symmetry and from
translational symmetry. We discuss the relevant experiments for pyrochlore U(1)
QSLs and further provide some insights to the pyrochlore Heisenberg model.Comment: 12 pages, to appear in PRResearch, a short explanation is found via
https://gangchengroup-physics.weebly.com/paper-explanation.htm
Cooper instability generated by attractive fermion-fermion interaction in the two-dimensional semi-Dirac semimetals
Cooper instability associated with superconductivity in the two-dimensional
semi-Dirac semimetals is attentively studied in the presence of attractive
Cooper-pairing interaction, which is the projection of an attractive
fermion-fermion interaction. Performing the standard renormalization group
analysis shows that the Cooper theorem is violated at zero chemical potential
but instead Cooper instability can be generated only if the absolute strength
of fermion-fermion coupling exceeds certain critical value and transfer
momentum is restricted to a confined region, which is determined by the initial
conditions. Rather, the Cooper theorem would be instantly restored once a
finite chemical potential is introduced and thus a chemical potential-tuned
phase transition is expected. Additionally, we briefly examine the effects of
impurity scatterings on the Cooper instability at zero chemical potential,
which in principle are harmful to Cooper instability although they can enhance
the density of states of systems. Furthermore, the influence of competition
between a finite chemical potential and impurities upon the Cooper instability
is also simply investigated. These results are expected to provide instructive
clues for exploring unconventional superconductors in the kinds of semimetals.Comment: 18 pages; 14 figure
Symmetry Enriched U(1) Topological Orders for Dipole-Octupole Doublets on a Pyrochlore Lattice
Symmetry plays a fundamental role in our understanding of both conventional
symmetry breaking phases and the more exotic quantum and topological phases of
matter. We explore the experimental signatures of symmetry enriched U(1)
quantum spin liquids (QSLs) on the pyrochlore lattice. We point out that the Ce
local moment of the newly discovered pyrochlore QSL candidate
CeSnO, is a dipole-octupole doublet. The generic model for these
unusual doublets supports two distinct symmetry enriched U(1) QSL ground states
in the corresponding quantum spin ice regimes. These two U(1) QSLs are dubbed
dipolar U(1) QSL and octupolar U(1) QSL. While the dipolar U(1) QSL has been
discussed in many contexts, the octupolar U(1) QSL is rather unique. Based on
the symmetry properties of the dipole-octupole doublets, we predict the
peculiar physical properties of the octupolar U(1) QSL, elucidating the unique
spectroscopic properties in the externalmagnetic fields. We further predict the
Anderson-Higgs transition from the octupolar U(1) QSL driven by the external
magnetic fields. We identify the experimental relevance with the candidate
material CeSnO and other dipole-octupole doublet systems.Comment: Published version. 6+3 pages, 3+1 figures, 1+1 table
Detecting spin fractionalization in a spinon Fermi surface spin liquid
Motivated by the recent proposal of the spinon Fermi surface spin liquids for
several candidate materials such as YbMgGaO4, we explore the experimental
consequences of the external magnetic fields on this exotic state.
Specifically, we focus on the weak field regime where the spin liquid state is
well preserved and the spinon remain to be a good description of the magnetic
excitations. From the spin-1/2 nature of the spinon excitation, we predict the
unique features of the spinon continuum when the weak magnetic field is applied
to the system. Due to the small energy scale of the exchange interactions
between the local moments in the spin liquid candidate like YbMgGaO4, our
proposal for the spectral weight shifts and spectral crossing in the magnetic
fields can be immediately tested by inelastic neutron scattering experiments.
Several other experimental aspects about the spinon Fermi surface and the
spinon excitations are discussed and proposed. Our work provides an
experimental scheme to examine the fractionalized spinon excitation and the
candidate spin liquid states in YbMgGaO4, the 6H-B phase of Ba3NiSb2O9 and
other relevant materials.Comment: 9 pages, 5 figures, modified title and discussio
Theory of spin polarization in mesoscopic spin-orbit coupling systems
We establish a general formalism of the bulk spin polarization (BSP) and the
current-based spin polarization (CSP) for mesoscopic ferromagnetic and
spin-orbit interaction (SOI) semiconducting systems. Based on this formalism,
we reveal the basic properties of BSP and CSP and their relationships. The BSP
describes the intrinsic spin polarized properties of devices. The CSP depends
on both intrinsic parameters of device and the incident current. For the
non-spin-polarized incident current with the inphase spin-phase coherence, CSP
equals to BSP. We give analytically the BSP and CSP of several typical
nanodevice models, ferromagnetic nanowire, Rashba nanowire and rings. These
results provide basic physical behaviors of BSP and CSP and their
relationships.Comment: 18 page
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