scholarly journals Unconventional superconductivity in a strongly correlated band-insulator without doping

2021 ◽  
Vol 4 (2) ◽  
Author(s):  
Anwesha Chattopadhyay ◽  
H R krishnamurthy ◽  
Arti Garg
Keyword(s):  
Magnetic Order ◽  
Superconducting Phase ◽  
The Other ◽  
Model Parameters ◽  
Unconventional Superconductivity ◽  
Strongly Correlated ◽  
Half Metal ◽  
Band Insulator ◽  
Half Filling ◽  
Paramagnetic Metal

We present a novel route for attaining unconventional superconductivity in a strongly correlated system without doping. In a simple model of a correlated band insulator at half-filling we demonstrate, based on a generalization of the projected wavefunctions method, that superconductivity emerges for a broad range of model parameters when e-e interactions and the bare band-gap are both much larger than the kinetic energy, provided the system has sufficient frustration against the magnetic order. As the interactions are tuned, the superconducting phase appears sandwiched between the correlated band insulator followed by a paramagnetic metal on one side, and a ferrimagnetic metal, antiferromagnetic half-metal, and Mott insulator phases on the other side.

scholarly journals Metal-insulator Phase Diagram for the Fully Diagonal Disordered Hubbard Model at Half-filling

2016 ◽  
Vol 26 (2) ◽  
pp. 159
Author(s):  
Hoang Anh Tuan ◽  
Nguyen Thi Hai Yen
Keyword(s):  
Phase Diagram ◽  
Mean Field Theory ◽  
Mean Field ◽  
Metallic State ◽  
Strongly Correlated ◽  
Potential Approximation ◽  
Metal Insulator ◽  
Band Insulator ◽  
Half Filling ◽  
Correlation Strength

The electronic properties of strongly correlated systems with binary type of disorder are investigated using the coherent potential approximation. For half-filled system, two transitions from a band insulator via a metallic state to a Mott insulator are found with increasing the correlation strength of only one of the constituents. Our phase diagram is consistent with those obtained by the dynamical mean field theory.

How the insulator and pseudogap states coalesce beneath the superconductor dome

2014 ◽  
Vol 28 (22) ◽  
pp. 1450146 ◽  
Author(s):  
Victor M. Martinez Alvarez ◽  
Alejandro Cabo-Bizet ◽  
Alejandro Cabo Montes de Oca
Keyword(s):  
Quantum Phase Transitions ◽  
Tight Binding ◽  
Spin Fluctuations ◽  
Hole Doping ◽  
Model Parameters ◽  
Hole Density ◽  
Lattice Symmetry ◽  
Half Filling ◽  
Paramagnetic Metal ◽  
Strong Spin

The pseudogap effects and the expected quantum phase transitions (QPTs) in cuprate materials are yet unclear in nature. A single band tight-binding (TB) model for the CuO 2 planes of these materials had predicted the existence of definite pseudogap states at half-filling, after considering that a crystal symmetry breaking and noncollinear spin orientations of the single particle states are allowed. Here we show that after including hole doping in the model, a QPT which lies beneath the superconducting dome exists and is a second-order one. In it, an antiferromagntic-insulator (AFI) ground state, showing strong spin fluctuations at low doping, coalesce with an excited paramagnetic pseudogap (PPG) state, exhibiting a broken lattice symmetry at the critical hole density. A critical doping value xc = 0.2 resulted, which surprisingly coincided with the experimentally measured one, in spite of the fact that the model parameters were not yet optimized. Above this value the system becomes a paramagnetic metal. The band structures and Fermi surface with doping are evaluated and their evolution show a close resemblance with the experimental observations, including the topological change in structure at the critical hole density.

scholarly journals Theory and Applications of the Unit Gamma/Gompertz Distribution

Mathematics ◽  
2021 ◽  
Vol 9 (16) ◽  
pp. 1850
Author(s):  
Rashad A. R. Bantan ◽  
Farrukh Jamal ◽  
Christophe Chesneau ◽  
Mohammed Elgarhy
Keyword(s):  
Stochastic Ordering ◽  
Real Data ◽  
Rate Function ◽  
The Other ◽  
Likelihood Method ◽  
Model Parameters ◽  
Data Sets ◽  
Gompertz Distribution ◽  
Probability And Statistics ◽  
Analytical Behavior

Unit distributions are commonly used in probability and statistics to describe useful quantities with values between 0 and 1, such as proportions, probabilities, and percentages. Some unit distributions are defined in a natural analytical manner, and the others are derived through the transformation of an existing distribution defined in a greater domain. In this article, we introduce the unit gamma/Gompertz distribution, founded on the inverse-exponential scheme and the gamma/Gompertz distribution. The gamma/Gompertz distribution is known to be a very flexible three-parameter lifetime distribution, and we aim to transpose this flexibility to the unit interval. First, we check this aspect with the analytical behavior of the primary functions. It is shown that the probability density function can be increasing, decreasing, “increasing-decreasing” and “decreasing-increasing”, with pliant asymmetric properties. On the other hand, the hazard rate function has monotonically increasing, decreasing, or constant shapes. We complete the theoretical part with some propositions on stochastic ordering, moments, quantiles, and the reliability coefficient. Practically, to estimate the model parameters from unit data, the maximum likelihood method is used. We present some simulation results to evaluate this method. Two applications using real data sets, one on trade shares and the other on flood levels, demonstrate the importance of the new model when compared to other unit models.

Study of Oscillating Flow of Viscoelastic Fluid With the Fractional Maxwell Model

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
Jiu-hong Jia ◽  
Hong-xing Hua
Keyword(s):  
Exact Solution ◽  
Petroleum Chemistry ◽  
Viscoelastic Fluid ◽  
Maxwell Model ◽  
The Other ◽  
Oscillating Flow ◽  
Model Parameters ◽  
Series Approximation ◽  
Phase Lags ◽  
Annular Effect

The oscillating flow of the viscoelastic fluid in cylindrical pipes has been applied in many fields, such as industries of petroleum, chemistry, and bioengineering. It is studied using the fractional derivative Maxwell model in this paper. The exact solution is obtained utilizing a simpler and more reasonable technique. According to this velocity solution, the time-velocity profile of one kind of viscoelastic fluid is analyzed. From analysis, it is found that the flow behaves like the Newton fluid when the oscillating frequency is low, and the flow reversal occurs when the oscillating frequency is high. Moreover, two series approximations for the velocity are obtained and analyzed for different model parameters. In one series approximation, the velocity is parabolic in profile, while in the other series approximation, the velocity presents three characteristics: (1) it is independent of radius and at the centerline is smaller than that of steady Poiseuille flow, (2) the phase lags about 90deg with respect to the imposed pressure gradient, and (3) the Richardson annular effect is found near the wall.

scholarly journals Bird Species Identification Using Spectrogram Based on Multi-Channel Fusion of DCNNs

Entropy ◽  
2021 ◽  
Vol 23 (11) ◽  
pp. 1507
Author(s):  
Feiyu Zhang ◽  
Luyang Zhang ◽  
Hongxiang Chen ◽  
Jiangjian Xie
Keyword(s):  
Species Identification ◽  
Feature Fusion ◽  
Bird Species ◽  
The Other ◽  
Identification Accuracy ◽  
Mean Average Precision ◽  
Training Dataset ◽  
Model Parameters ◽  
Average Precision ◽  
Fusion Mode

Deep convolutional neural networks (DCNNs) have achieved breakthrough performance on bird species identification using a spectrogram of bird vocalization. Aiming at the imbalance of the bird vocalization dataset, a single feature identification model (SFIM) with residual blocks and modified, weighted, cross-entropy function was proposed. To further improve the identification accuracy, two multi-channel fusion methods were built with three SFIMs. One of these fused the outputs of the feature extraction parts of three SFIMs (feature fusion mode), the other fused the outputs of the classifiers of three SFIMs (result fusion mode). The SFIMs were trained with three different kinds of spectrograms, which were calculated through short-time Fourier transform, mel-frequency cepstrum transform and chirplet transform, respectively. To overcome the shortage of the huge number of trainable model parameters, transfer learning was used in the multi-channel models. Using our own vocalization dataset as a sample set, it is found that the result fusion mode model outperforms the other proposed models, the best mean average precision (MAP) reaches 0.914. Choosing three durations of spectrograms, 100 ms, 300 ms and 500 ms for comparison, the results reveal that the 300 ms duration is the best for our own dataset. The duration is suggested to be determined based on the duration distribution of bird syllables. As for the performance with the training dataset of BirdCLEF2019, the highest classification mean average precision (cmAP) reached 0.135, which means the proposed model has certain generalization ability.

scholarly journals Effectiveness of Information from Vehicles beyond Nearest Vehicle Ahead for Traffic Flow

2011 ◽  
Vol 2011 ◽  
pp. 1-7
Author(s):  
Hikaru Shimizu ◽  
Sho Nishiyama ◽  
Yukiko Wakita ◽  
Eisuke Kita
Keyword(s):  
Stability Analysis ◽  
Traffic Flow ◽  
Flow Simulation ◽  
The Other ◽  
Stable Region ◽  
Model Parameters ◽  
Model Stability ◽  
Acceleration Rate ◽  
Traffic Flow Simulation ◽  
Vehicle Acceleration

A driver usually controls the vehicle according to only the information from the nearest leader vehicle. If the information from the other leader vehicles is also available, the driver can control the vehicle more adequately. The aim of this study is to discuss the effectiveness of the information from the other leader vehicles than the nearest one for the traffic flow. For this purpose, the traffic flow is modeled by using the Chandler-type multi-vehicle-following model. This model changes the vehicle acceleration rate according to the velocity differences between the vehicle and its multileader vehicles. After the model stability analysis, the traffic flow simulation is performed. The results reveal that the stable region of the model parameters expands according to the increase of the number of the leader vehicles.

Study on Logistics Resources Integration Based on Sustainable Logistics Networking in Manufacturing Engineering

2013 ◽  
Vol 340 ◽  
pp. 145-149
Author(s):  
Zhang Yi
Keyword(s):  
International Markets ◽  
The Other ◽  
Strongly Correlated ◽  
Logistics Industry ◽  
Sustainable Logistics ◽  
High Efficient ◽  
National Economic ◽  
National Competition ◽  
Competition Ability

The development of logistics is strongly correlated to the comprehensive economy development. Logistics plays the key role of correlating the other nine main economic industries, and transporting goods and service within the domestic and international markets. It is strongly demanded that the adjustment and revitalization of logistics industry shall satisfy the logistics industry upgrade itself, and increase the competition ability of other economic sections, so as to provide stable, high-efficient business running environments for the other industries as well. It is of great strategic meaning for the adjustment, restructuring and upgrading of the national economic system, thus comprehensively strengthening the national competition ability. The State Council of China has made a series of revitalization plans for the logistics industry, which has been integrated into development plan of the macroeconomic system.

Strongly correlated transition metal oxides

2019 ◽  
Author(s):  
Ελένη Αζά
Keyword(s):  
Dielectric Permittivity ◽  
Single Crystal ◽  
Single Crystals ◽  
Long Range ◽  
Ground State ◽  
Degrees Of Freedom ◽  
Magnetic Order ◽  
Range Order ◽  
Long Range Order ◽  
Strongly Correlated

The discovery of materials with coexisting magnetic and ferroelectric orders, has revived theinterest of condensed matter physics and materials’ science communities maintaining the greatpromise of such fundamental mechanisms in devising applications ranging from portablemagnetoelectric (ME) sensors and memories to radar technologies. The present PhD thesis is a study in the field of strongly correlated systems where coupled properties arise from the interplay of charge and spin degrees of freedom over lattice topologies enabling competing magnetic interactions and therefore emergence of coupling of electric and magnetic order. Non-perovskite, two-dimensional (2D) Na-Mn-O oxides are revisited in scope of this in both polycrystalline and large single crystal forms. Among Na-deficient polymorphs, hexagonal α-Na0.7MnO2 (single crystals) has been investigated for the first time as a playground of competing interactions due to mixed Mnvalence (Mn4+ / Mn3+), fostered by Na vacancies in the structure. The competition of FM (Mn3+-Mn4+) and AFM (Mn3+ -Mn3+) interactions is believed to be the origin of the magnetic instability leading to a glassy ground state leaving also their footprint in the dielectric permittivity measurements. Competing FM and AFΜ interactions are also investigated as the origin of the anisotropic magnetic properties witnessed in a-NaxMnO2 (x= 0.96) single crystals. Neutron single crystal experiments show a well-established AFM long range order which vanishes above 26 K whilea coexistent canted antiferromagnetic state persists up to 45 K. In both alpha powders and aNa0.96MnO2 single crystals, the dielectric permittivity suggests the onset of the commensuratemagnetic long range order (T~ 45 K) which in the case of the powders allows a magnetocapacitance effect. Compositional modulations in β-NaMnO2, which are depicted as an intergrowth of α- and βlike oxygen coordinations, are found to trigger a proper-screw magnetic ground state which evolves into collinear commensurate AFM state. Features in the dielectric permittivity coincide with the onset of the commensurate AFM order giving away also the contribution of the α- structural domains. Further understanding of the mechanisms that dictate the relief of frustrated interactions and establishment of magnetic order together with the role of structural complexity in the form of domains or domain-walls is a direction that warrants further exploration as it will help us to resolve whether other coupled electron degrees of freedom are likely to be generated in this family of oxides.

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