5,503 research outputs found
Zero-field Kondo splitting and quantum-critical transition in double quantum dots
Double quantum dots offer unique possibilities for the study of many-body
correlations. A system containing one Kondo dot and one effectively
noninteracting dot maps onto a single-impurity Anderson model with a structured
(nonconstant) density of states. Numerical renormalization-group calculations
show that while band filtering through the resonant dot splits the Kondo
resonance, the singlet ground state is robust. The system can also be
continuously tuned to create a pseudogapped density of states and access a
quantum critical point separating Kondo and non-Kondo phases.Comment: 4 pages, 4 figures; Accepted for publication in Physical Review
Letter
Exchange interaction effects in the thermodynamic properties of quantum dots
We study electron-electron interaction effects in the thermodynamic
properties of quantum-dot systems. We obtain the direct and exchange
contributions to the specific heat C_v in the self-consistent Hartree-Fock
approximation at finite temperatures. An exchange-induced phase transition is
observed and the transition temperature is shown to be inversely proportional
to the size of the system. The exchange contribution to C_v dominates over the
direct and kinetic contributions in the intermediate regime of interaction
strength (r_s ~ 1). Furthermore, the electron-electron interaction modifies
both the amplitude and the period of magnetic field induced oscillations in
C_v.Comment: 4 pages, 4 figures; To appear in Phys. Rev.
Impurity-enhanced Aharonov-Bohm effect in neutral quantum-ring magnetoexcitons
We study the role of impurity scattering on the photoluminescence (PL)
emission of polarized magnetoexcitons. We consider systems where both the
electron and hole are confined on a ring structure (quantum rings) as well as
on a type-II quantum dot. Despite their neutral character, excitons exhibit
strong modulation of energy and oscillator strength in the presence of magnetic
fields. Scattering impurities enhance the PL intensity on otherwise "dark"
magnetic field windows and non-zero PL emission appears for a wide magnetic
field range even at zero temperature. For higher temperatures, impurity-induced
anticrossings on the excitonic spectrum lead to unexpected peaks and valleys on
the PL intensity as function of magnetic field. Such behavior is absent on
ideal systems and can account for prominent features in recent experimental
results.Comment: 7 pages, 7 figures, RevTe
Mapeamento pedológico detalhado da bacia do córrego Águas da Lúcia, município de Botucatu- SP.
A área de 1.894 ha da bacia do Córrego Águas da Lúcia, localizada no município de Botucatu - SP foi selecionada para mapeamento pedológico detalhado a fim de produzir uma base de dados confiável para fins de pesquisa em solos e manejo sustentado de bacias hidrográficas com solos frágeis. Através da amostragem dos pontos de análise de solos, da descrição morfológica de perfis no campo, coleta de material dos horizontes pedogenéticos e análises físicas e químicas em laboratório foi possível classificar os solos da bacia e delinear cinco unidades de mapeamento. A partir deste levantamento, a bacia apresentou solos com baixo teor de argila, de textura arenosa e média, pouco acúmulo de carbono em superfície, baixa fertilidade natural e uma distribuição bastante homogênea das classes d e solo justificando o uso de um levantamento detalhado até o quinto nível categórico do Sistema Brasileiro de Classificação de Solos
Inheritance of resistance to soybean cyst nematode races 3 and 14 in soybean RIL and F2 populations.
The objective of this work was to evaluate the soybean inheritance of resistance to cyst nematode races 3 and 14. The following populations where evaluated: one population of recombinant inbred lines (RILs) [Hartwig (resistant) x Y23 (susceptible line)] for races 3, 14 and 9; one population of families F2:3 [M-SOY 8001 (resistant) x MB/BR 46 -Conquista (susceptible)] for race 3; and one population of families F2:3 [(S5995 (resistant) x BRSMG Renascença (susceptible)] for race 14. In RIL populations, four epistatic genes were identified which conditioned resistance to race 14, and three epistatic ones for resistance to races 3 and 9. The lack of one gene provided moderate resistance under all situations. The highest number of genes for resistance to race 14 points out that genes responsible for lower effects might be involved. In population F2:3 from M-SOY 8001 x MB/BR 46 - Conquista, one recessive gene for moderate resistance and two recessive genes complete resistance to race 3 were identified. Two recessive genes conditioning moderate resistance to race 14 were identified in population F2:3 from the crossing S5995 x BRSMG Renascença. These results will be useful in designing crossings, involving these parentals, with higher possibility to accumulating genes that provide resistance to several SCN races
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