Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userKondo Effect and Persistent Currents in a Mesoscopic Ring: Numerically Exact Results
309
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We study the persistent current circulating along a mesoscopic ring with a dot side-coupled to it when threaded by a magnetic field. A cluster including the dot and its vicinity is diagonalized and embedded into the rest of the system. The result is numerically exact. We show that a ring of any size can be in the Kondo regime, although for small sizes it depends upon the magnetic flux. In the Kondo regime, the current can be a smooth or a strongly dependent function of the gate potential according to the structure of occupation of the highest energetic electrons of the system.
rate research
Read More
We calculate the contribution of superconducting fluctuations to the mesoscopic persistent current of an ensemble of rings, each made of a superconducting layer in contact with a normal one, in the Cooper limit. The superconducting transition temperature of the bilayer decays very quickly with the increase of the relative width of the normal layer. In contrast, when the Thouless energy is larger than the temperature then the suppression of the persistent current with the increase of this relative width is much slower than that of the transition temperature. This effect is similar to that predicted for magnetic impurities, although the proximity effect considered here results in pair-weakening as opposed to pair-breaking.
A double quantum dot device, connected to two channels that only see each other through interdot Coulomb repulsion, is analyzed using the numerical renormalization group technique. By using a two-impurity Anderson model, and parameter values obtained from experiment [S. Amasha {it et al.}, Phys. Rev. Lett. {bf 110}, 046604 (2013)], it is shown that, by applying a moderate magnetic field, and adjusting the gate potential of each quantum dot, opposing spin polarizations are created in each channel. Furthermore, through a well defined change in the gate potentials, the polarizations can be reversed. This polarization effect is clearly associated to a spin-orbital Kondo state having a Kondo peak that originates from spatially separated parts of the device. This fact opens the exciting possibility of experimentally probing the internal structure of an SU(2) Kondo state.
We discuss the emergence of zero-energy Majorana modes in a disordered finite-length p-wave one-dimensional superconducting ring, pierced by a magnetic flux $Phi$ tuned at an appropriate value $Phi=Phi_*$. In the absence of fermion parity conservation, we evidence the emergence of the Majorana modes by looking at the discontinuities in the persistent current $I[Phi]$ at $Phi=Phi_*$. By monitoring the discontinuities in $I[Phi]$, we map out the region in parameter space characterized by the emergence of Majorana modes in the disordered ring.
We revisit here the Kibble-Zurek mechanism for superfluid bosons slowly driven across the transition towards the Mott-insulating phase. By means of a combination of the Time-Dependent Variational Principle and a Tree-Tensor Network, we characterize the current flowing during annealing in a ring-shaped one-dimensional Bose-Hubbard model with artificial classical gauge field on up to 32 lattice sites. We find that the superfluid current shows, after an initial decrease, persistent oscillations which survive even when the system is well inside the Mott insulating phase. We demonstrate that the amplitude of such oscillations is connected to the residual energy, characterizing the creation of defects while crossing the quantum critical point, while their frequency matches the spectral gap in the Mott insulating phase. Our predictions can be verified in future atomtronics experiments with neutral atoms in ring shaped traps. We believe that the proposed setup provides an interesting but simple platform to study the non-equilibrium quantum dynamics of persistent currents experimentally.
We study the interplay of interactions and topology in a pseudo-spin Weyl system, obtained from a minimally modified Hubbard model, using the numerically exact auxiliary-field quantum Monte Carlo method complemented by mean-field theory. We find that the pseudo-spin plays a key role in the pairing mechanism, and its effect is reflected in the structure of the pairing amplitude. An attractive on-site interaction leads to pairing between quasiparticles carrying opposite spin and opposite topological charge, resulting in the formation of real-spin singlet pairs that are a mixture of pseudo-spin singlet and pseudo-spin triplet. Our results provide a detailed characterization of the exotic pairing behavior in this system, and represent an important step towards a more complete understanding of superconductivity in the context of topological band structures, which will help guide searches for topological superconductivity in real materials and ultracold atoms.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
