Controlling conductance statistics of quantum wires by driving ac fields

We calculate the entire distribution of the conductance P(G) of a one-dimensional disordered system --quantum wire-- subject to a time-dependent field. Our calculations are based on Floquet theory and a scaling approach to localization. Effects of the applied ac field on the conductance statistics can be strong and in some cases dramatic, as in the high-frequency regime where the conductance distribution shows a sharp cut-off. In this frequency regime, the conductance is written as a product of a frequency-dependent term and a field independent term, the latter containing the information on the disorder in the wire. We thus use the solution of the Mel'nikov equation for time-independent transport to calculate P(G) at any degree of disorder. At lower frequencies, it is found that the conductance distribution and the correlations of the transmission Floquet modes are described by a solution of the Dorokhov-Mello-Pereyra-Kumar equation with an effective number of channels. In the regime of strong localization, induced by the disorder or the ac field, P(G) is a log-normal distribution. Our theoretical results are verified numerically using a single-band Anderson Hamiltonian.Comment: 6 pages, 4 figures. V2: a new reference added. Minor correction

Chiral bound states in the continuum

We present a distinct mechanism for the formation of bound states in the continuum (BICs). In chiral quantum systems there appear zero-energy states in which the wave function has finite amplitude only in one of the subsystems defined by the chiral symmetry. When the system is coupled to leads with a continuum energy band, part of these states remain bound. We derive some algebraic rules for the number of these states depending on the dimensionality and rank of the total Hamiltonian. We examine the transport properties of such systems including the appearance of Fano resonances in some limiting cases. Finally, we discuss experimental setups based on microwave dielectric resonators and atoms in optical lattices where these predictions can be tested.Comment: 9 pages, 8 figures. v2: includes results specific to honeycomb lattice; matches published versio

Commensurability effects for fermionic atoms trapped in 1D optical lattices

Fermionic atoms in two different hyperfine states confined in optical lattices show strong commensurability effects due to the interplay between the atomic density wave (ADW) ordering and the lattice potential. We show that spatially separated regions of commensurable and incommensurable phases can coexist. The commensurability between the harmonic trap and the lattice sites can be used to control the amplitude of the atomic density waves in the central region of the trap.Comment: Accepted for publication in Physical Review Letter

Interacting electron systems between Fermi leads: effective one-body transmissions and correlation clouds

In order to extend the Landauer formulation of quantum transport to correlated fermions, we consider a spinless system in which charge carriers interact, connected to two reservoirs by non-interacting one-dimensional leads. We show that the mapping of the embedded many-body scatterer onto an effective one-body scatterer with interaction-dependent parameters requires to include parts of the attached leads where the interacting region induces power law correlations. Physically, this gives a dependence of the conductance of a mesoscopic scatterer upon the nature of the used leads which is due to electron interactions inside the scatterer. To show this, we consider two identical correlated systems connected by a non-interacting lead of length $L\_\mathrm{C}$. We demonstrate that the effective one-body transmission of the ensemble deviates by an amount $A/L\_\mathrm{C}$ from the behavior obtained assuming an effective one-body description for each element and the combination law of scatterers in series. $A$ is maximum for the interaction strength $U$ around which the Luttinger liquid becomes a Mott insulator in the used model, and vanishes when $U \to 0$ and $U \to \infty$. Analogies with the Kondo problem are pointed out.Comment: 5 pages, 6 figure

Morbiditat i mortalitat de rapinyaires ingressades al CRFS de Torreferrussa

Els resultats d'una investigació centrada en aus rapinyaires ingressades al Centre de Recuperació de Fauna Salvatge de Torreferrussa constata que les causes d'ingrés més freqüents són les antropogèniques, entre les quals destaca la importància dels trets. La tricomoniasis, per altra banda, és la malaltia amb major prevalença. Pel que fa a la rehabilitació dels ocells, el balanç és negatiu, amb només un 47,2% d'aus alliberades al medi natural. La valoració en conjunt d'aquests i altres paràmetres permet identificar factors de risc per a cada espècie.Los resultados de una investigación centrada en aves rapaces en el Centro de Recuperación de Fauna Salvaje de Torreferrussa constata que las causas de ingreso más frecuentes son las antropogénicas, entre las que destaca la importancia de los disparos. La tricomoniasis, por otra parte, es la enfermedad con mayor prevalencia. En cuanto a la rehabilitación de las rapaces diurnas y nocturnas, el balance es negativo, con sólo un 47,2% de aves liberadas en el medio natural. La valoración en conjunto de estos y otros parámetros permite identificar factores de riesgo para cada especie