1,378 research outputs found
First principles calculation of conductance in monovalent atomic contacts: quantization and even-odd behavior
No full textEven-odd behavior of conductance in monatomic sodium wires
No full textWith the aid of the Friedel sum rule, we perform first-principles calculations of conductances through monatomic Na wires, taking into account the sharp tip geometry and discrete atomic structure of electrodes. We find that conductances (G) depend on the number (L) of atoms in the wires; G is G(0)(= 2e(2)/h) for odd L, independent of the wire geometry, while G is generally smaller than G(0) and sensitive to the wire structure for even L. This even-odd behavior is attributed to the charge neutrality and resonant character due to the sharp tip structure. We suggest that similar even-odd behavior may appear in other monovalent atomic wires.We thank Y.-G. Jin for his advice on the efficient
real-space multigrid method. We also acknowledge helpful
discussions with Professor C. S. Kim and Professor J.
Yu. This work was supported by the QSRC at Dongkuk
University.
Even-odd behavior and quantization of conductance in monovalent atomic contacts
No full textA Friedel-sum-rule-aided first-principles conductance calculation is presented for a sodium monatomic wire suspended between two bulk electrodes with sharp tip geometry. The conductance (G) is found to oscillate with the number (L) of atoms in the wire. For odd L, G has a quantized value of G(0) (=2e(2)/h), which is robust to the variation in wire geometry, while G is smaller than G(0) for even L, sensitive to the wire geometry. This even-odd behavior results from the sharp electrode tip and charge neutrality; the former generates resonant states, and the latter pins one of the resonant states at the Fermi energy for odd L. (C) 2002 Elsevier Science B.V. All rights reserved
Nonequilibrium dephasing in an electronic Mach-Zehnder interferometer
No full textWe study nonequilibrium dephasing in an electronic Mach-Zehnder interferometer. We demonstrate that the shot noise at the beam splitter of the interferometer generates an ensemble of nonequilibrium electron density configurations and that electron interactions induce configuration-specific phase shifts of an interfering electron. The resulting dephasing exhibits two characteristic features, a lobe pattern in the visibility and phase jumps of pi, in good agreement with experimental data.open1139sciescopu
Cylindrocarpon root rot: multi-gene analysis reveals novel species within the Ilyonectria radicicola species complex
No full textIlyonectria radicicola and its Cylindrocarpon-like anamorph represent a species complex that is commonly associated with root rot disease symptoms on a range of hosts. During the course of this study, several species could be distinguished from I. radicicola sensu stricto based on morphological and culture characteristics. DNA sequence analysis of the partial ß-tubulin, histone H3, translation elongation factor 1-a and nuclear ribosomal RNA-Internal Transcribed Spacer (nrRNA-ITS) genes were employed to provide further support for the morphological species resolved among 68 isolates associated with root rot disease symptoms. Of the various loci screened, nrRNA-ITS sequences were the least informative, while histone H3 sequences were the most informative, resolving the same number of species as the combined dataset across the four genes. Within the Ilyonectria radicicola species complex, 12 new taxa are delineated occurring on a diverse range of hosts, the most common being Cyclamen, Lilium, Panax, Pseudotsuga, Quercus and Vitis
Recidiva da neoplasia da cérvix uterina após tratamento cirúrgico primário.
No full textTrabalho de Conclusão de Curso - Universidade Federal de Santa Catarina, Centro de Ciências da Saúde, Departamento de Tocoginecologia, Curso de Medicina, Florianópolis, 199
Electronic interferometer capacitively coupled to a quantum dot
No full textWe theoretically study electron interference in a ballistic electronic interferometer capacitively coupled to a quantum dot. The visibility of the interference is reduced when the dot has degenerate ground states with different excess charges. The degree of the reduction depends on system parameters such as the strength of the capacitive coupling, and the dependence is analyzed in the regime where the dwell time of electrons in the dot is much longer than the electron flight time through the interferometry region coupled to the dot. The result is consistent with recent experimental data.open1133sciescopu
Visibility recovery by strong interaction in an electronic Mach-Zehnder interferometer
No full textWe study the evolution of a single-electron packet of Lorentzian shape along an edge of the integer quantum Hall regime or in a Mach-Zehnder interferometer, considering a capacitive Coulomb interaction and using a bosonization approach. When the packet propagates along a chiral quantum Hall edge, we find that its electron density profile becomes more distorted from Lorentzian due to the generation of electron-hole excitations, as the interaction strength increases yet stays in a weak-interaction regime. However, as the interaction strength becomes larger and enters a strong-interaction regime, the distortion becomes weaker and eventually the Lorentzian packet shape is recovered. The recovery of the packet shape leads to an interesting feature of the interference visibility of the symmetric Mach-Zehnder interferometer whose two arms have the same interaction strength. As the interaction strength increases, the visibility decreases from the maximum value in the weak-interaction regime and then increases to the maximum value in the strong-interaction regime. We argue that this counterintuitive result also occurs under other types of interactions. DOI: 10.1103/PhysRevB.86.235444open111sciescopu
Towards unified understanding of conductance of stretched monatomic contacts
No full textWhen monatomic contacts are stretched, their conductance behaves in qualitatively different ways depending on their constituent atomic elements. Under a single assumption of resonance formation, we show that various conductance behaviors can be understood in a unified way in terms of the response of the resonance to stretching. This analysis clarifies the crucial roles played by the number of valence electrons, charge neutrality, and orbital shapes.open1114sciescopu
Revival of Electron Coherence in a Quantum Wire of Finite Length
No full textWe study the spatial decay of electron coherence due to electron-electron interaction in a finite-length disorder-free quantum wire. Based on the Luttinger liquid theory, we demonstrate that the coherence length characterizing the exponential decay of the coherence can vary from region to region, and that the coherence can even revive after the decay. This counterintuitive behavior, which is in clear contrast to the conventional exponential decay with single coherence length, is due to the fractionalization of an electron and the finite-size-induced recombination of the fractions.open115sciescopu
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