Abstract
We study the Kondo alloy model on a square lattice using dynamical mean-field theory for Kondo substitution and disorder effects, together with static mean-field approximations. We computed ...and analyzed photoemission properties as a function of electronic filling
n
c
, Kondo impurity concentration
x
, and strength of Kondo temperature
T
K
. We provide a complete description of the angle resolved photoemission spectroscopy (ARPES) signals expected in the paramagnetic (PM) Kondo phases. By analyzing the Fermi surface (FS), we observe the Lifshitz-like transition predicted previously for strong
T
K
at
x
=
n
c
and we discuss the evolution of the dispersion from the dense coherent to the dilute Kondo regimes. At smaller
T
K
, we find that this transition marking the breakdown of coherence at
x
=
n
c
becomes a crossover. However, we identify another transition at a smaller concentration
x
⋆
where the effective mass continuously vanishes.
x
⋆
separates the one-branch and the two-branches ARPES dispersions characterizing respectively dilute and dense Kondo PM regimes. The
x
−
T
K
phase diagrams are also described, suggesting that the transition at
x
⋆
might be experimentally observable since magnetically ordered phases are stabilized at much lower
T
K
. FS reconstructions in antiferromagnetic and ferromagnetic phases are also discussed.
Abstract
The analysis showed that the most important results of the Aviation Industry Development Strategy are: an increase in the share of Russian manufacturers of aviation products in the world ...market; reorientation of the production of aviation industrial complex to the innovative segment of the global market. The aim of the study is to develop an engineering mechanism for the modernization of science-intensive products of the aviation industry. In accordance with this, a method is proposed for assessing the strategic risk of high technology products, a model for assessing the effectiveness of modernization of high technology products based on the concept of strategic risk as defining elements of the engineering process in the aviation industry. The practical implementation of the model is carried out.
We consider a magnetic impurity deposited on the surface of a strong topological insulator and interacting with the surface modes by a Kondo exchange interaction. Taking into account the warping of ...the Fermi line of the surface modes, we derive a mapping to an effective one-dimensional model and show that the impurity is fully screened by the surface electrons except when the Fermi level lies exactly at the Dirac point. Using an Abrikosov fermion mean-field theory, we calculate the shape of the electronic density Friedel oscillation resulting from the presence of the Kondo screening cloud. We analyze quantitatively the observability of a sixfold symmetry in the Friedel oscillations for two prototype compounds: Bi sub(2) Se sub(3) and Bi sub(2) Te sub(3).
We argue that near a Kondo breakdown critical point, a spin liquid with spatial modulations can form. Unlike its uniform counterpart, we find that this occurs via a second order phase transition. The ...amount of entropy quenched when ordering is of the same magnitude as for an antiferromagnet. Moreover, the two states are competitive, and at low temperatures are separated by a first order phase transition. The modulated spin liquid we find breaks Z4 symmetry, as recently seen in the hidden order phase of URu2Si2. Based on this, we suggest that the modulated spin liquid is a viable candidate for this unique phase of matter.
We present a theoretical model of spin transitions in stacks of molecular layers. Our model captures the already established physics of these systems (thermal hysteretic transitions and crossovers) ...and suggests a way towards in situ control of this physics by means of an external electric field. Our results pave the way toward both temperature and voltage controllable organic memory.
In aviation technology, constant improvement in production processes and management methods is associated with the creation of components on the basis of innovative materials. The development of new ...composites and alloys requires their optimal use in airplanes. The potential use of innovative materials depends on the model for the creation of digital twins. A neural network model for creating the digital twin of composites used in aircraft production is developed.
In certain Mott-insulating dimerized antiferromagnets, triplet excitations of the paramagnetic phase display both three-particle and four-particle interactions. When such a magnet undergoes a quantum ...phase transition into a magnetically ordered state, the three-particle interaction becomes part of the critical theory provided that the lattice ordering wave vector is zero. One microscopic example is the staggered-dimer antiferromagnet on the square lattice, for which deviations from O(3) universality have been reported in numerical studies. Using both symmetry arguments and microscopic calculations, we show that a nontrivial cubic term arises in the relevant order-parameter quantum field theory, and we assess its consequences using a combination of analytical and numerical methods. We also present finite-temperature quantum Monte Carlo data for the staggered-dimer antiferromagnetwhich complement recently published results. The data can be consistently interpreted in terms of critical exponents identical to that of the standard O(3) universality class, but with anomalously large corrections to scaling. We argue that the cubic interaction of critical triplons, although irrelevant in two spatial dimensions, is responsible for the leading corrections to scaling due to its small scaling dimension.
Strategic Risk of Drones Burdina, A. A.; Moskvicheva, N. V.; Burdin, S. S.
Russian engineering research,
2021/8, Letnik:
41, Številka:
8
Journal Article
Recenzirano
The feasibility of pilotless aerial vehicles (drones) is considered. Their properties are identified and compared with those of piloted vehicles. The strategic risk of a high-tech product ...characterizes its technological novelty and the degree to which it meets the design goals. The portfolio components of the strategic risk for drones are noted. A method of assessing each portfolio component and the strategic risk as a whole is outlined for pilotless aerial vehicles.
We study the competition between the Kondo effect and frustrating exchange interactions in a Kondo-lattice model within a large-${\cal N}$ dynamical mean-field theory. We find a T=0 phase transition ...between a heavy Fermi-liquid and a spin-liquid for a critical value of the exchange $J_c = T_{K}^0$, the single-impurity Kondo temperature. Close to the critical point, the Fermi liquid coherence scale $T^\star$ is strongly reduced and the effective mass strongly enhanced. The regime $T>T^\star$ is characterized by spin-liquid magnetic correlations and non-Fermi-liquid properties. It is suggested that magnetic frustration is a general mechanism which is essential to explain the large effective mass of some metallic compounds such as LiV$_2$O$_4$.
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