Twisted bilayer graphene near the magic angle
exhibits rich electron-correlation physics, displaying insulating
, magnetic
and superconducting phases
. The electronic bands of this system were ...predicted
to narrow markedly
near the magic angle, leading to a variety of possible symmetry-breaking ground states
. Here, using measurements of the local electronic compressibility, we show that these correlated phases originate from a high-energy state with an unusual sequence of band population. As carriers are added to the system, the four electronic 'flavours', which correspond to the spin and valley degrees of freedom, are not filled equally. Rather, they are populated through a sequence of sharp phase transitions, which appear as strong asymmetric jumps of the electronic compressibility near integer fillings of the moiré lattice. At each transition, a single spin/valley flavour takes all the carriers from its partially filled peers, 'resetting' them to the vicinity of the charge neutrality point. As a result, the Dirac-like character observed near charge neutrality reappears after each integer filling. Measurement of the in-plane magnetic field dependence of the chemical potential near filling factor one reveals a large spontaneous magnetization, further substantiating this picture of a cascade of symmetry breaking. The sequence of phase transitions and Dirac revivals is observed at temperatures well above the onset of the superconducting and correlated insulating states. This indicates that the state that we report here, with its strongly broken electronic flavour symmetry and revived Dirac-like electronic character, is important in the physics of magic-angle graphene, forming the parent state out of which the more fragile superconducting and correlated insulating ground states emerge.
Quantum Plasmas Haas, Fernando
2011, 20110727, 2011-08-28, Letnik:
65
eBook
This book provides an overview of the basic concepts and new methods in the emerging scientific area known as quantum plasmas. In the near future, quantum effects in plasmas will be unavoidable, ...particularly in high density scenarios such as those in the next-generation intense laser-solid density plasma experiment or in compact astrophysics objects. Currently, plasmas are in the forefront of many intriguing questions around the transition from microscopic to macroscopic modeling of charged particle systems. Quantum Plasmas: an Hydrodynamic Approach is devoted to the quantum hydrodynamic model paradigm, which, unlike straight quantum kinetic theory, is much more amenable to investigate the nonlinear realm of quantum plasmas. The reader will have a step-by-step construction of the quantum hydrodynamic method applied to plasmas. The book is intended for specialists in classical plasma physics interested in methods of quantum plasma theory, as well as scientists interested in common aspects of two major areas of knowledge: plasma and quantum theory.In these chapters, the quantum hydrodynamic model for plasmas, which has continuously evolved over the past decade, will be summarized to include both the development and applications of the method.
The combined efforts of the Physicists and the Economists in recent years in analyzing and modelling various dynamic phenomena in monetary and social systems have led to encouraging developments, ...generally classified under the title of Econophysics. These developments share a common ambition with the already established field of Quantitative Economics. This volume intends to offer the reader a glimpse of these two parallel initiatives by collecting review papers written by well-known experts in the respective research frontiers in one cover. This massive book presents a unique combination of research papers contributed almost equally by Physicists and Economists. Additional contributions from Computer Scientists and Mathematicians are also included in this volume. The book consists of two parts: the first part concentrates on Econophysics problems and the second part stresses on various quantitative issues in Economics. Both parts specialize on frontier problems in Games and Social Choices.
Stochastic energetics is the emerging field that bridges the gap between stochastic dynamical processes and thermodynamics. This book is the first introductory text on the field and gradually takes ...readers from the basics to applications.
•MXene doped composite CMAC was prepared by ultrasound–assisted electrostatic self–assembly.•CMAC exhibited high adsorption performance for the tested three anionic dyes.•Classical models and ASPM ...were both applied to elucidate the adsorption mechanism.•The adsorption mechanism was the synergistic effect of physicochemical interactions.
In this paper, a porous adsorbent synthesized from biomass activated carbon and MXene, named as CMAC composite, was utilized for the removal of three anionic azo dyes, allure red (AR), congo red (CR) and sunset yellow (SY). The formation of this heterostructure adsorbent was achieved by electrostatic self–assembly of negatively charged 2D MXene nanosheets and activated carbon with the assistance of a cationic surfactant (CTAB) solution. This method impeded the re–stacking of MXene nanosheets, effectively reduced the multilayer plate structure of MXene and enlarged the layer spacing, thus promoting the exposure of available active sites to further enhance the adsorption performance. The CMAC was physicochemically characterized via different analytical techniques and the dye adsorption isotherms at three temperatures were quantified. The experimental results showed that CMAC displayed excellent adsorption efficiency for CR with adsorption capacities above 1400 mg/g. The adsorption of the dyes coincided with the Langmuir model, pseudo–second order kinetic model and intraparticle diffusion model. A multilayer statistical physical model was employed to explain the adsorption mechanism between the tested dyes and CMAC. The simulation results provided the possible adsorption directions of the dye molecules on the adsorbent surface under different operating conditions, and the decrease of the active sites density DM indicated that the aggregation of dye molecules existed only when CMAC adsorbed SY. The adsorption energy calculations showed that the adsorption of AR and CR by CMAC was heat–absorbing and the adsorption of SY was exothermic. The adsorption mechanism can be attributed to the synergistic effect of physical adsorption, hydrogen bonding and electrostatic interactions.
Fractional Dynamics: Applications of Fractional Calculus to Dynamics of Particles, Fields and Media' presents applications of fractional calculus, integral and differential equations of non-integer ...orders in describing systems with long-time memory, non-local spatial and fractal properties. Mathematical models of fractal media and distributions, generalized dynamical systems and discrete maps, non-local statistical mechanics and kinetics, dynamics of open quantum systems, the hydrodynamics and electrodynamics of complex media with non-local properties and memory are considered. This book is intended to meet the needs of scientists and graduate students in physics, mechanics and applied mathematics who are interested in electrodynamics, statistical and condensed matter physics, quantum dynamics, complex media theories and kinetics, discrete maps and lattice models, and nonlinear dynamics and chaos. Dr. Vasily E. Tarasov is a Senior Research Associate at Nuclear Physics Institute of Moscow State University and an Associate Professor at Applied Mathematics and Physics Department of Moscow Aviation Institute.
The microscopically complicated real world exhibits behavior that often yields to simple yet quantitatively accurate descriptions. Predictions are possible despite large uncertainties in microscopic ...parameters, both in physics and in multiparameter models in other areas of science. We connect the two by analyzing parameter sensitivities in a prototypical continuum theory (diffusion) and at a self-similar critical point (the Ising model). We trace the emergence of an effective theory for long-scale observables to a compression of the parameter space quantified by the eigenvalues of the Fisher Information Matrix. A similar compression appears ubiquitously in models taken from diverse areas of science, suggesting that the parameter space structure underlying effective continuum and universal theories in physics also permits predictive modeling more generally.
The usage of various herbicides in the agricultural field leads to water pollution which is a big threat to the environment. Herein, the pods of the Peltophorum pterocarpum tree were used as a cheap ...resource to synthesize activated carbon (AC) by low-temperature carbonization to remove 2,4-dichlorophenoxyacetic acid (2,4-D) – an abundantly used herbicide. The exceptional surface area (1078.34 m2/g), mesoporous structure, and the various functional groups of the prepared AC adsorbed 2,4-D effectively. The maximum adsorption capacity was 255.12 mg/g, significantly higher than the existing AC adsorbents. The adsorption data satisfactorily modelled using Langmuir and pseudo-second-order models. Also, the adsorption mechanism was studied using a statistical physics model which substantiated the multi-molecular interaction of 2,4-D with the AC. The adsorption energy (<20 kJ/mol) and thermodynamic studies (ΔH°: −19.50 kJ/mol) revealed the physisorption and exothermicity. The practical application of the AC was successfully tested in various waterbodies by spiking experiments. Hence, this work confirms that the AC prepared from the pods of P. pterocarpum can be applied as a potential adsorbent to remove herbicides from polluted waterbodies.
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•Mesoporous activated carbon derived from Peltophorum pterocarpum resulted in exceptional surface area of 1078.34 m2/g.•Removal efficiency reached 94% at pH 2 with sorption capacity of 255.12 mg/g.•Monolayer with single energy model was fitted with the experimental isotherm data.•Significant results (>90%) were obtained on removing 2,4-D from spiked waterbodies.
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