1,108 research outputs found
Dissecting Quantum Phase Transition in the Transverse Ising Model
Irrespective of the fact that a complete theoretical description of critical
phenomena in connection with phase transition has been well-established through
the renormalization group formalism, the understanding of the phase transition
itself remains incomplete. For example, the questions like why and how the
phase transition happens are still unclear. Here we provide a pattern picture
to dissect the quantum phase transition occurring in the transverse Ising model
for a finite lattice. After the validity of the pattern formulation obtained is
confirmed, the energy contributions of different patterns to the ground state
energy provide a sufficient detail to show why and how the phase transition
takes place. Furthermore, a histogram of patterns' occupancy calculated by the
projections of ground state wavefunction on the patterns also shows the
detailed process of the phase transition. Our results are not only fundamental
in understanding the mechanism of phase transition, but also of practical
interest in quantum simulation platforms.Comment: 6 pages, 4 figure
Dissecting Superradiant Phase Transition in the Quantum Rabi Model
The phase transition is both thermodynamically and quantum-mechanically
ubiquitous in nature or laboratory and its understanding is still one of most
active issues in modern physics and related disciplines. The Landau's theory
provides a general framework to describe \textit{phenomenologically} the phase
transition by the introduction of order parameters and the associated symmetry
breakings; and is also taken as starting point to explore the critical
phenomena in connection with phase transitions in renormalization group, which
provides a complete theoretical description of the behavior close to the
critical points. In this sense the microscopic mechanism of the phase
transition remains still to be uncovered. Here we make a first attempt to
explore the microscopic mechanism of the superradiant phase transition in the
quantum Rabi model (QRM). We firstly perform a diagonalization in an operator
space to obtain three fundamental patterns involved in the QRM and then analyze
explicitly their energy evolutions with increasing coupling strengths. The
characteristic behaviors found uncover the microscipic mechanism of the
superradiant phase transition: one is active to drive the happening of phase
transition, the second responses rapidly to the change of the active pattern
and wakes up the third pattern to stablize the new phase. This kind of
dissecting mechanism explains for the first time why and how happens the
superradiant phase transition in the QRM and paves a way to explore the
microscopic mechanism of the phase transitions happening popularly in nature.Comment: 6 pages, 5 figure
Pattern description of the ground state properties of the one-dimensional axial next-nearest-neighbor Ising model in a transverse field
The description and understanding of the consequences of competing
interactions in various systems, both classical and quantum, are notoriously
difficult due to insufficient information involved in conventional concepts,
for example, order parameters and/or correlation functions. Here we go beyond
these conventional language and present a pattern picture to describe and
understand the frustration physics by taking the one-dimensional (1D) axial
next-nearest-neighbor Ising (ANNNI) model in a transverse field as an example.
The system is dissected by the patterns, obtained by diagnonalizing the model
Hamiltonian in an operator space with a finite lattice size (: natural
number) and periodic boundary condition. With increasing the frustration
parameter, the system experiences successively various phases/metastates,
identified respectively as those with zero, two, four, ,
domains/kinks, where the first is the ferromagnetic phase and the last the
antiphase. Except for the ferromagnetic phase and antiphase, the others should
be metastates, whose transitions are crossing over in nature. The results
clarify the controversial issues about the phases in the 1D ANNNI model and
provide a starting point to study more complicated situations, for example, the
frustration systems in high dimensions.Comment: 6 pages, 5 figure
An explicit evolution from N\'eel to striped antiferromagnetic states in the spin-1/2 - Heisenberg model on the square lattice
The frustrated spin- Heisenberg model on the square lattice
has been extensively studied since 1988 because of its close relationship to
the high-temperature superconductivity in cuprates and more importantly
involved novel phase of matter in its own right, namely, quantum spin liquid
(QSL), one of hot topics in condensed matter physics in recent years. However,
the phase diagram of the model, particularly in the maximally frustrated regime
, is quite controversial, and more seriously the nature of
the QSL is not clear at all. Here we provide a pattern picture, on one hand, to
show explicitly how the system evolves from the N\'eel antiferromagnetic (AFM)
state at small to the striped AFM one at large ; on the other hand,
to uncover the nature of the QSL if it exists in the intermediate
coupling regime. For simplicity, we show our results by taking the square
lattice with size here and periodic boundary
condition is considered, and furthermore, exact diagonalization is employed to
confirm the correctness of our picture. Our results indicate that the highly
frustration regime is characterized by diagonal two-domain, while the N\'eel
AFM state has a diagonal single-domain and the striped AFM state shows itself
as a diagonal four-domain, namely, completely diagonal antiferromagnetic order,
in the present case. Increasing the system size, the number of the diagonal
domains increases correspondingly, but the diagonal single-domain for the
N\'eel AFM state and the diagonal -domain for the striped AFM state
remain unchanged. Our results shed light on the understanding of the QSL.Comment: 6 pages, 4 figure
Study on the Sedimentation Roughness in the Perennial Reach of the Three Gorges Reservoir
Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchive
CTSN: Predicting Cloth Deformation for Skeleton-based Characters with a Two-stream Skinning Network
We present a novel learning method to predict the cloth deformation for
skeleton-based characters with a two-stream network. The characters processed
in our approach are not limited to humans, and can be other skeletal-based
representations of non-human targets such as fish or pets. We use a novel
network architecture which consists of skeleton-based and mesh-based residual
networks to learn the coarse and wrinkle features as the overall residual from
the template cloth mesh. Our network is used to predict the deformation for
loose or tight-fitting clothing or dresses. We ensure that the memory footprint
of our network is low, and thereby result in reduced storage and computational
requirements. In practice, our prediction for a single cloth mesh for the
skeleton-based character takes about 7 milliseconds on an NVIDIA GeForce RTX
3090 GPU. Compared with prior methods, our network can generate fine
deformation results with details and wrinkles.Comment: 13 page
Quantumness and quantum to classical transition in the generalized Rabi model
The quantum to classical transition (QCT) is one of the central mysteries in
quantum physics. This process is generally interpreted as state collapse from
measurement or decoherence from interacting with the environment. Here we
define the quantumness of a Hamiltonian by the free energy difference between
its quantum and classical descriptions, which vanishes during QCT. We apply
this criterion to the many-body Rabi model and study its scaling law across the
phase transition, finding that not only the temperature and Planck constant,
but also all the model parameters are important for this transition. We show
that the Jaynes-Cummings and anti Jaynes-Cummings models exhibit greater
quantumness than the Rabi model. Moreover, we show that the rotating wave and
anti-rotating wave terms in this model have opposite quantumness in QCT. We
demonstrate that the quantumness may be enhanced or suppressed at the critical
point. Finally, we estimate the quantumness of the Rabi model in current
trapped ion experiments. The quantumness provides an important tool to
characterize the QCT in a vast number of many-body models.Comment: 6 pages, 5 figure
The Study of Microwave and Electric Hybrid Sintering Process of AZO Target
We simulated the microwave sintering of ZnO by 3D modelling. A large-size Al-doped ZnO (AZO) green ceramic compact was prepared by slurry casting. Through studying the microwave and electric hybrid sintering of the green compact, a relative density of up to 98.1% could be obtained by starting microwave heating at 1200°C and increasing the power 20 min later to 4 kW for an AZO ceramic target measuring 120 × 240 × 12 mm. The resistivity of AZO targets sintered with microwave assistance was investigated. The energy consumption of sintering could be greatly reduced by this heating method. Until now, few studies have been reported on the microwave and electric hybrid sintering of large-size AZO ceramic targets. This research can aid in developing sintering technology for large-size high-quality oxide ceramic targets
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