Shot noise in resonant tunneling through an interacting quantum dot with intradot spin-flip scattering

In this paper, we present theoretical investigation of the zero-frequency shot noise spectra in electron tunneling through an interacting quantum dot connected to two ferromagnetic leads with possibility of spin-flip scattering between the two spin states by means of the recently developed bias-voltage and temperature dependent quantum rate equations. For this purpose, a generalization of the traditional generation-recombination approach is made for properly taking into account the coherent superposition of electronic states, i.e., the nondiagonal density matrix elements. Our numerical calculations find that the Fano factor increases with increasing the polarization of the two leads, but decreases with increasing the intradot spin-flip scattering.Comment: Some typos correction. 6 pages, 3 figures, based on work presented at the 2004 IEEE NTC Quantum Device Technology Workshop, accepted for publication by IEEE transactions on Nanotechnolog

Super-Poissonian shot noise in the resonant tunneling due to coupling with a localized level

We report our studies of the shot noise spectrum in tunneling through an interacting quantum dot when an additional single-level quantum dot without tunnel coupling to leads is coherently side-connected to it. We show that the zero-frequency shot noise could reach a super-Poissonian value for appropriate ratios between dot-dot hoppings and dot-lead couplings, but the current is independent on the hopping. Moreover, the frequency spectrum of shot noise shows an obvious peak at the Rabi frequency, which is controllable by tuning the dot-lead couplings.Comment: 3 pages, 3 figures, Appl. Phys. Lett.(in press

Magnetic-flux-controlled giant Fano factor for the coherent tunneling through a parallel double-quantum-dot

We report our studies of zero-frequency shot noise in tunneling through a parallel-coupled quantum dot interferometer by employing number-resolved quantum rate equations. We show that the combination of quantum interference effect between two pathways and strong Coulomb repulsion could result in a giant Fano factor, which is controllable by tuning the enclosed magnetic flux.Comment: 11 pages, 2 figure

Quantum Electroweak Symmetry Breaking Through Loop Quadratic Contributions

Based on two postulations that (i) the Higgs boson has a large bare mass $m_H \gg m_h \simeq 125$ GeV at the characteristic energy scale $M_c$ which defines the standard model (SM) in the ultraviolet region, and (ii) quadratic contributions of Feynman loop diagrams in quantum field theories are physically meaningful, we show that the SM electroweak symmetry breaking is induced by the quadratic contributions from loop effects. As the quadratic running of Higgs mass parameter leads to an additive renormalization, which distinguishes from the logarithmic running with a multiplicative renormalization, the symmetry breaking occurs once the sliding energy scale $\mu$ moves from $M_c$ down to a transition scale $\mu =\Lambda_{EW}$ at which the additive renormalized Higgs mass parameter $m^2_H(M_c/\mu)$ gets to change the sign. With the input of current experimental data, this symmetry breaking energy scale is found to be $\Lambda_{EW}\simeq 760$ GeV, which provides another basic energy scale for the SM besides $M_c$. Studying such a symmetry breaking mechanism could play an important role in understanding both the hierarchy problem and naturalness problem. It also provides a possible way to explore the experimental implications of the quadratic contributions as $\Lambda_{EW}$ lies within the probing reach of the LHC and the future Great Collider.Comment: 10 pages, 2 figures, published versio

Pumped spin-current and shot noise spectra in a single quantum dot

We exploit the pumped spin-current and current noise spectra under equilibrium condition in a single quantum dot connected to two normal leads, as an electrical scheme for detection of the electron spin resonance (ESR) and decoherence. We propose spin-resolved quantum rate equations with correlation functions in Laplace-space for the analytical derivation of the zero-frequency atuo- and cross-shot noise spectra of charge- and spin-current. Our results show that in the strong Coulomb blockade regime, ESR-induced spin flip generates a finite spin-current and the quantum partition noises in the absence of net charge transport. Moreover, spin shot noise is closely related to the magnetic Rabi frequency and decoherence and would be a sensitive tool to measure them.Comment: 4 pages, 3 figures, to be published in Phys. Rev. Lette