In underdoped cuprates, the interplay of the pseudogap, superconductivity, and charge and spin ordering can give rise to exotic quantum states, including the pair density wave (PDW), in which the ...superconducting (SC) order parameter is oscillatory in space. However, the evidence for a PDW state remains inconclusive and its broader relevance to cuprate physics is an open question. To test the interlayer frustration, the crucial component of the PDW picture, we perform transport measurements on charge- and spin-stripe-ordered La
Eu
Sr
CuO
and La
Nd
Sr
CuO
in perpendicular magnetic fields (H
), and also with an additional field applied parallel to CuO
layers (H
). We detect several phenomena predicted to arise from the existence of a PDW, including an enhancement of interlayer SC phase coherence with increasing H
. These data also provide much-needed transport signatures of the PDW in the regime where superconductivity is destroyed by quantum phase fluctuations.
Abstract
The origin of the weak insulating behavior of the resistivity, i.e.
$${\rho }_{xx}\propto {\mathrm{ln}}\,(1/T)$$
ρ
x
x
∝
ln
(
1
/
T
)
, revealed when magnetic fields (
H
) suppress ...superconductivity in underdoped cuprates has been a longtime mystery. Surprisingly, the high-field behavior of the resistivity observed recently in charge- and spin-stripe-ordered La-214 cuprates suggests a metallic, as opposed to insulating, high-field normal state. Here we report the vanishing of the Hall coefficient in this field-revealed normal state for all
$$T\ <\ (2-6){T}_{{\rm{c}}}^{0}$$
T
<
(
2
−
6
)
T
c
0
, where
$${T}_{{\rm{c}}}^{0}$$
T
c
0
is the zero-field superconducting transition temperature. Our measurements demonstrate that this is a robust fundamental property of the normal state of cuprates with intertwined orders, exhibited in the previously unexplored regime of
T
and
H
. The behavior of the high-field Hall coefficient is fundamentally different from that in other cuprates such as YBa
2
Cu
3
O
6+
x
and YBa
2
Cu
4
O
8
, and may imply an approximate particle-hole symmetry that is unique to stripe-ordered cuprates. Our results highlight the important role of the competing orders in determining the normal state of cuprates.
Abstract
The absence of thermalization in certain isolated many-body systems is of great fundamental interest. Many-body localization (MBL) is a widely studied mechanism for thermalization to fail in ...strongly disordered quantum systems, but it is still not understood precisely how the range of interactions affects the dynamical behavior and the existence of MBL, especially in dimensions
D
> 1. By investigating nonequilibrium dynamics in strongly disordered
D
= 2 electron systems with power-law interactions ∝ 1/
r
α
and poor coupling to a thermal bath, here we observe MBL-like, prethermal dynamics for
α
= 3. In contrast, for
α
= 1, the system thermalizes, although the dynamics is glassy. Our results provide important insights for theory, especially since we obtained them on systems that are much closer to the thermodynamic limit than synthetic quantum systems employed in previous studies of MBL. Thus, our work is a key step towards further studies of ergodicity breaking and quantum entanglement in real materials.
Photovoltaic power plants represent a good solution concerning electric energy supply under the condition that there are sufficiently available and suitable areas for their mounting. This study ...supports an opinion hypothesis that the City of Požarevac has at its disposal a considerable potential for energy production by photovoltaic power plants at the degraded areas. The geographic information systems were used to identify and create polygons for degraded areas, and the Energy capacity assessment tool was used in order to estimate the solar potential for this areas. The results showed that it would be possible to generate about 43% of the electric energy produced by thermal power plants “Kostolac A” and “Kostolac B” by construction and work of photovoltaic power plants in proposed locations. For a long-term standpoint, this project would prevent the emission of over 30 million tons of CO2 into the atmosphere. This study should contribute to the better understanding of local authorities regarding the potential for the use of solar energy, as well as, define of better principles, measures, instruments and policy to stimulate the application of solar energy to secure the requirements for electric energy.
A study of the temperature (T) and density (ns) dependence of conductivity σ(ns,T) of a highly disordered, two-dimensional (2D) electron system in Si demonstrates scaling behavior consistent with the ...existence of a metal-insulator transition (MIT). The same critical exponents are found when the Coulomb interaction is screened by the metallic gate and when it is unscreened or long range. The results strongly suggest the existence of a disorder-dominated 2D MIT, which is not directly affected by the range of the Coulomb interactions.
We report the fabrication of hexagonal-boron-nitride (hBN) encapsulated multiterminal WSe2 Hall bars with 2D/2D low-temperature Ohmic contacts as a platform for investigating the two-dimensional (2D) ...metal–insulator transition. We demonstrate that the WSe2 devices exhibit Ohmic behavior down to 0.25 K and at low enough excitation voltages to avoid current-heating effects. Additionally, the high-quality hBN-encapsulated WSe2 devices in ideal Hall-bar geometry enable us to accurately determine the carrier density. Measurements of the temperature (T) and density (n s) dependence of the conductivity σ(T, n s) demonstrate scaling behavior consistent with a metal–insulator quantum phase transition driven by electron–electron interactions but where disorder-induced local magnetic moments are also present. Our findings pave the way for further studies of the fundamental quantum mechanical properties of 2D transition metal dichalcogenides using the same contact engineering.
In the underdoped pseudogap regime of cuprate superconductors, the normal state is commonly probed by applying a magnetic field (H). However, the nature of the H-induced resistive state has been the ...subject of a long-term debate, and clear evidence for a zero-temperature H-tuned superconductor-insulator transition has proved elusive. Here we report magnetoresistance measurements on underdoped La2-xSrxCuO4, providing striking evidence for quantum-critical behaviour of the resistivity--the signature of a H-driven superconductor-insulator transition. The transition is not direct, being accompanied by the emergence of an intermediate state, which is a superconductor only at temperature T = 0. Our finding of a two-stage H-driven superconductor-insulator transition goes beyond the conventional scenario in which a single quantum critical point separates the superconductor and the insulator in the presence of a perpendicular magnetic field. Similar two-stage H-driven superconductor-insulator transitions, in which both disorder and quantum phase fluctuations play an important role, may also be expected in other copper-oxide high-temperature superconductors.
Keywords: internal control, internal audit, financial management and control INTRODUCTION Modern management by top management in agricultural enterprises imposes a real need for improving business ...decision-making. In addition to the essential improvement of business decision-making by top management, numerous authors emphasize the importance of the application of numerous international standards, such as the application of international accounting standards, financial reporting standards, standards of the auditing profession and others, which was pointed out by numerous authors (Wang et al., 2014; Wang, 2016; Popovic et al., 216; Quattrone, 2017; Popovic et al., 2017; Toms, 2019; Radovic et al., 2019). Based on the mentioned Law, the starting point of the authors of the study was that medium-sized agricultural enterprises in the last year of operation meet at least two of the following criteria: * have an average of 50 to 250 employees per year, * that they have achieved an annual income of 8,000 to 40,000 average gross earnings of employees in the Republic of Serbia, * that the average annual property value is in the range of 6,000 to 30,000 of the average gross salary of employees in the Republic. According to that criterion, the observation was made in relation to the use of: internal audits, internal controls and the use of financial management and control mechanisms.
Organic farming preserve and upgrade the biodiversity of the soil and biodiversity of the entire ecosystem by protecting the environment, plants, and human health. This study analyses organic plant ...production worldwide and in Montenegro (2000-2020) and discusses the prospects and challenges in developing organic plant production. Geographically, Montenegro has a diverse climate, suitable for the production of more types of fields crops, vegetables and fruits throughout the year. The paper compares the area of organic farms, the number of farmers, and share of organic in the overall agricultural land in the world and Montenegro, Europe, and several European countries similar to Montenegro in terms of relief or area (Switzerland, Slovenia, Slovakia, Estonia, Serbia, and Cyprus). Data were also analysed for a mountainous state, such as Switzerland, and a Mediterranean one, as Cyprus, as by its position and relief, Montenegro is at the same time a mountainous (northern) and a Mediterranean country (southern region). Shows are trends in plant production areas in Montenegro since it gained independence (2006) and comparison with the EU countries. Grassland production prevails in Montenegro with 85.89%, followed by fruit (12.26%) and cereals (1.62%). The total area under organic vegetable covered a small area compared to the production of fodder crops (3951.84 ha), fruit (563.98 ha), medicinal and aromatic plants (232.46 ha) and field crops (74.49 ha). Organic fruit production has the largest share in the northern part of Montenegro. Certified organic production brings benefits because health-safe products are a condition for preserving the environment and health.
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