arXiv subjects

Pedro A. Orellana

Publications and source records attributed to Pedro A. Orellana.

17 recordsLinked to original sources

arXiv2026

Exceptional-Point Geometry of Weak Topological Boundary States

In this article, we demonstrate that weak topology can be formulated geometrically in terms of exceptional singularities of an analytically continued Bloch Hamiltonian. A general plaquette chiral model in two dimensions serves as a minimal realization of dual weak topology, possessing two independent families of weak topological invariants, one for each spatial direction. The weak-topological edge states correspond to exceptional points in complex momentum space, while corner zero modes emerge from exceptional curves obtained by complexifying both momenta. Compact localized states arise when the exceptional roots collapse to the origin. This framework provides a unified complex-momentum description of edge, corner, and compact localization.

cond-mat.mes-hall↗

arXiv2026

Interplay of bound states in the continuum and Fano--Andreev interference in a hybrid triple quantum dot

We investigate bound states in the continuum (BICs) in a hybrid normal--superconducting triple quantum dot system, where the central dot is coupled to two normal leads and the lateral dots are proximity-coupled to superconducting electrodes. Local electron--electron interactions are treated within the Hubbard approximation. Finite bias, together with lateral-dot detuning and superconducting proximity, induces interference between elastic electron tunneling (ET) and Andreev reflection (AR) channels, mediated by BIC-related modes and proximity-induced Andreev bound states. As the bias is swept through the subgap resonances, ET exhibits sharp antiresonances that evolve into exact transport zeros, signaling the emergence of (quasi-)BICs. We further find a continuous crossover from a Fano--Andreev BIC-supported regime to a Fano--Andreev quasi-BIC regime as the detuning asymmetry increases. The formation of BICs and quasi-BICs is accompanied by a pronounced change in the occupation of the side quantum dot, providing an internal diagnostic directly correlated with the transport signatures of the bound states.

cond-mat.mes-hall↗

arXiv2025

Observation of multi-orbital Fano resonances in photonic lattices

Fano resonances are a fundamental physical phenomenon that occurs when an open channel couples with a closed one, resulting in a resonant cancellation of transmission. In this article, we introduce a quantum simulator designed to observe multi-orbital Fano resonances using a photonic waveguide analog. The system consists of a homogeneous lattice, which includes a plane wave generator, and an atom-like impurity that supports first-order (S) and second-order (P) modes. We derive a two-impurity Fano-Anderson model to describe this system and fit the experimental results accordingly, demonstrating a remarkable agreement between our experimental measurements and theoretical predictions. A comprehensive experimental characterization reveals clear double resonances for the S and P states, which depend on the properties of the atom and the excitation wavelength. Our results illustrate how the transport of a propagating beam on a lattice can be effectively controlled by simply adjusting the properties of a single external atom-like impurity, which works as an efficient energy valve.

physics.optics↗

arXiv2024

Fragile dislocation modes in obstructed atomic topological phases

We here introduce the concept of fragile topological dislocation modes, which are localized only in a fraction of a topological phase, while otherwise leak into the bulk continuum. We show that such dislocation modes are hosted in an obstructed atomic topological phase in the two-dimensional Su-Schrieffer-Heeger model, but only in a finite region with an indirect gap at high energy. These dislocation modes are realized as chiral pairs at finite energies with protection stemming from a combination of the chiral (unitary particle-hole) and the point group (C$_{4v}$) symmetries, but only when the indirect gap is open. In this regime, we corroborate the stability of the defect modes by following their localization and also by explicitly adding a weak chemical potential disorder. Our findings, therefore, should be consequential for the experimental observation of such modes in designer topological crystals and classical metamaterials.

cond-mat.mes-hall↗

arXiv2024

Beyond symmetry-protected BICs: transmission through asymmetric crossbar junctions in one-dimensional waveguides

Over the last few decades, the study of Bound States in the Continuum, their formation, and properties has attracted lots of attention, especially in optics and photonics. It is particularly noticeable that most of these investigations base their studies on symmetric systems. In this article, we study the formation of bound states in the continuum in electronic and photonic transport systems consisting of crossbar junctions formed by one-dimensional waveguides, considering asymmetric junctions with commensurable lengths for the upper and lower arms. We also study how BICs form in linear junction arrays as a function of the distance between consecutive junctions and their commensurability with the upper and lower arms. We solve the Helmholtz equation for the crossbar junctions and calculate the transmission probability, probability density in the intersections, and quality factor. The presence of quasi-BICs is reflected in the transmission probability as a sharp resonance in the middle of a symmetric Fano resonance along with Dirac's delta functions in the probability density and divergence in the quality factors.

physics.optics↗

arXiv2023

Fano-Andreev effect in a T-shaped Double Quantum Dot in the Coulomb blockade regime

We studied the effects of superconducting quantum correlations in a system consisting of two quantum dots, two normal leads, and a superconductor. Using the non-equilibrium Green's functions method, we analyzed the transmission, density of states, and differential conductance of electrons between the normal leads. We found that the superconducting correlations resulted in Fano-Andreev interference, which is characterized by two anti-resonance line shapes in all of these quantities. This behavior was observed in both equilibrium and non-equilibrium regimes and persisted even when Coulomb correlations were taken into account using the Hubbard-I approximation. It is worth noting that the robustness of this behavior against these conditions has not been studied previously in the literature.

cond-mat.mes-hall↗

arXiv2022

Bound states in the continuum in a two-channel Fano-Anderson model

In this article, we study the formation of the bound states in the continuum (BICs) in a two-channel Fano-Anderson model. We employ the Green's function formalism, together with the equation of motion method, to analyze the relevant observables, such as the transmission coefficient and the density of states. Most importantly, our results show that the system hosts true BICs for the case of a symmetric configuration with the degenerate impurity levels, and a complete transmission channel is then suppressed. Finally, we argue that the proposed mechanism could be relevant for the realization of BICs in the electronic and photonic systems.

cond-mat.mes-hall↗

arXiv2020

Majorana Bound States hallmark in a quantum topological interferometer ring

In this work, we investigate the conductance and current correlations properties of a quantum topological inteferometer consisting of a QD coupled to two Majorana Bound States (MBSs) confined at both ends of a 1D topological superconductor ring nanowire. We analyze the ring in its topological non trivial and trivial phases to show that the tunneling conductance, shot noise and fano factor present unique characteristics to distinguish the hallmark of MBSs. We reinforce our findings by taking advantage of the correspondence between the quantum topological interferometer and a dot effectively coupled to a single Majorana state in a straight topological superconductor wire configuration. We show that, besides the characteristic zero-bias conductance $e^{2} /2h$ and the already known shot noise features, the Fano factor provides significant information to distinguish the MBSs presence.

cond-mat.mes-hall↗

arXiv2019

Equivalence between a topological and non-topological quantum dot - hybrid structures

In this work, we demonstrate an equivalence on the single-electron transport properties between systems of different nature, a topological quantum system and a (conventional) non-topological one. Our results predicts that the Fano resonances obtained in a T-shaped double quantum dot system coupled to two normal leads and one superconducting lead (QD-QD-S) are identical to the obtained in a ring system composed of a quantum dot coupled to two Majorana bound states confined at the ends of a one dimensional topological superconductor nanowire (QD-MBSs). We show that the non-zero value of the Fano (anti)resonance in the conductance of the QD-MBSs systems is due to a complex Fano factor qM , which is identical to the complex Fano factor qS of the QD-QD-S. The complex nature of qS can be understood as a sign of a phase introduced by the superconducting lead in the QD-QD-S. It is because of this phase that the equivalence between the QD-QD-S and the QD-MBSs is possible. We believe that our results can motivate further theoretical and experimental works toward the understanding of transport properties of topological quantum hybrid structures from conventional non-topological quantum systems.

cond-mat.mes-hall↗

arXiv2013

Fano-Kondo and the Kondo-box regimes crossover in a quantum dot coupled to a quantum box

In this work,we study the Kondo effect of a quantum dot (QD) connected to leads and to a discrete set of one particle states provided by a quantum box represented by a quantum ring (QR) pierced by a magnetic flux side attached to the QD. The interplay between the bulk Kondo effect and the so called Kondo box regime is studied. In this system the QR energies can be continuously modified by the application of the magnetic field. The crossover between these two regimes is analyzed by changing the connection of the QD to the QR from the weak to the strong coupling regime. In the weak coupling regime, the differential conductance develops a sequence of Fano-Kondo antiresonances due to destructive interferences between the discrete quantum ring levels and the conducting Kondo channel provided by the leads. In the strong coupling regime the differential conductance has very sharp resonances when one of the Kondo discrete sub-level characterizing the Kondo box is tunned by the applied potential. The conductance, the current fluctuations and the Fano coefficient result to be the relevant physical magnitudes to be analyzed to reveal the physical properties of these two Kondo regimes and the crossover region between them. The results were obtained by using the Slave Boson Mean Field Theory (SBMFT).

cond-mat.mes-hall↗

arXiv2012

Graphene nanoring as a tunable source of polarized electrons

We propose a novel spin filter based on a graphene nanoring fabricated above a ferromagnetic strip. The exchange interaction between the magnetic moments of the ions in the ferromagnet and the electron spin splits the electronic states, and gives rise to spin polarization of the conductance and the total electric current. We demonstrate that both the current and its polarization can be controlled by a side-gate voltage. This opens the possibility to use the proposed device as a tunable source of polarized electrons.

cond-mat.mes-hall↗

arXiv2006

Kondo and Dicke effect in quantum-dots side coupled to a quantum wire

Electron tunneling through quantum-dots side coupled to a quantum wire, in equilibrium and nonequilibrium Kondo regime, is studied. The mean-field finite-$U$ slave-boson formalism is used to obtain the solution of the problem. We have found that the transmission spectrum shows a structure with two anti-resonances localized at the renormalized energies of the quantum dots. The DOS of the system shows that when the Kondo correlations are dominant there are two Kondo regimes with its own Kondo temperature. The above behavior of the DOS can be explained by quantum interference in the transmission through the two different resonance states of the quantum dots coupled to common leads. This result is analogous to the Dicke effect in optics. We investigate the many body Kondo states as a function of the parameters of the system.

cond-mat.mes-hall↗

arXiv2004

Kondo effect in side coupled double quantum-dot molecule

Electron tunneling through a double quantum dot molecule side attached to a quantum wire, in the Kondo regime, is studied. The mean-field finite-U slave-boson formalism is used to obtain the solution of the problem. We found conductance cancelations when the molecular energies of the side attached double quantum-dot cross the Fermi energy. We investigate the many body molecular Kondo states as a function of the parameters of the system.

cond-mat.mes-hall↗

arXiv2003

Kondo effect in a double quantum-dot molecule under the effect of an electric and magnetic field

Electron tunneling through a double quantum dot molecule, in the Kondo regime, under the effect of a magnetic field and an applied voltage, is studied. This system possesses a complex response to the applied fields characterized by a tristable solution for the conductance. The different nature of the solutions are studied in and out thermodynamical equilibrium. It is shown that the interdot coupling and the fields can be used to control the region of multistability. The mean-field slave-boson formalism is used to obtain the solution of the problem.

cond-mat.mes-hall↗

arXiv2003

Ghost Fano resonance in a double quantum dot molecule attached to leads

We study the electronic transport through a double quantum dot molecule attached to leads, and examine the transition from a configuration in series to a symmetrical parallel geometry. We find that a progressive reduction of the tunneling through the antibonding state takes place as a result of the destructive quantum interference between the different pathways through the molecule. The Fano resonance narrows down, disappearing entirely when the configuration is totally symmetric, so that only the bonding state participates of the transmission. In this limit the antibonding state becomes completely localized.

cond-mat.mes-hall↗

arXiv2002

Tristability in a non-equilibrium double-quantum-dot in Kondo regime

Electron tunneling through a non-equilibrium double quantum dot in the Kondo regime is studied. In the region of negative differential resistance, it is shown that this system possesses a complex response to the applied potential characterized by a tristable solution for the current. Increasing the applied potential or reducing the inter-dot coupling, the system goes through a transition from a coherent inter-dot regime to an incoherent one. The different nature of the solutions are characterized and it is shown that the effects of the asymmetry in the dot-lead coupling can be used to control the region of multistability. The mean-field slave-boson formalism is used to obtain the solution of the problem.

cond-mat.mes-hall↗

arXiv2001

Kondo effect and bistability in a double-quantum-dot

We study theoretically the out-of-equilibrium transport properties of a double quantum dot system in the Kondo regime. We model the system by means of a two-impurity Anderson Hamiltonian. The transport properties are characterized by Kondo effect properties, however, superimposed them, the system possesses novel non-linear bistability behavior.

cond-mat.mes-hall↗