178 research outputs found
Spin dependent conductance of a quantum dot side attached to topological superconductors as a probe of Majorana fermion states
Spin-polarized transport through a quantum dot side attached to a topological
superconductor and coupled to a pair of normal leads is discussed in Coulomb
and Kondo regimes. For discussion of Coulomb range equation of motion method
with extended Hubbard I approximation is used and Kondo regime is analyzed by
Kotliar-Ruckenstein slave boson approach. Apart from the occurrence of zero
bias anomaly the presence of Majorana states reflects also in splitting of
Coulomb lines. In the region of Coulomb borders the spin dependent negative
differential conductance is observed. Due to the low energy scale of Kondo
effect this probe allows for detection of Majorana states even for extremely
weak coupling with topological wire. In this range no signatures of Majorana
states appear in Coulomb blockade dominated transport.Comment: 3 pages, 3 figure
Electron-phonon interaction and electronic correlations in transport through electrostatically and tunnel coupled quantum dots
We investigate two equivalent capacitively and tunnel coupled quantum dots,
each coupled to its own pair of leads. Local Holstein type electron-phonon
coupling at the dots is assumed. To study many-body effects we use the finite-U
mean-field slave boson approach. For vanishing interdot interaction, weak e-ph
coupling and finite tunneling, molecular orbital spin Kondo effects occur for
single electron or single hole occupations. Phonons influence both correlations
and tunneling and additionally they shift the energies of the dots. Depending
on the dot energies and the strength of electron-phonon coupling, the system is
occupied by a different number of electrons that effectively interact with each
other repulsively or attractively leading to a number of different ground
states of DQD. Among them are Kondo-like states with spin, orbital or charge
correlations resulting from polaron cotunneling processes and states with
magnetic intersite correlations.Comment: 8 pages, 5 figure
Continuum radiative heat transfer modeling in media consisting of optically distinct components in the limit of geometrical optics
Continuum-scale equations of radiative transfer and corresponding boundary conditions are derived for a general case of a multi-component medium consisting of arbitrary-type, non-isothermal and non-uniform components in the limit of geometrical optics. The link between the discrete and continuum scales is established by volume averaging of the discrete-scale equations of radiative transfer by applying the spatial averaging theorem. Precise definitions of the continuum-scale radiative properties are formulated while accounting for the radiative interactions between the components at their interfaces. Possible applications and simplifications of the presented general equations are discussed
Fibre-optic delivery of time and frequency to VLBI station
The quality of Very Long Baseline Interferometry (VLBI) radio observations
predominantly relies on precise and ultra-stable time and frequency (T&F)
standards, usually hydrogen masers (HM), maintained locally at each VLBI
station. Here, we present an operational solution in which the VLBI
observations are routinely carried out without use of a local HM, but using
remote synchronization via a stabilized, long-distance fibre-optic link. The
T&F reference signals, traceable to international atomic timescale (TAI), are
delivered to the VLBI station from a dedicated timekeeping laboratory.
Moreover, we describe a proof-of-concept experiment where the VLBI station is
synchronized to a remote strontium optical lattice clock during the
observation.Comment: 8 pages, 8 figures, matches the version published in A&A, section
Astronomical instrumentatio
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