Exact spectral function of a Tonks-Girardeau gas in a lattice

The single-particle spectral function of a strongly correlated system is an essential ingredient to describe its dynamics and transport properties. We develop a general method to calculate the exact spectral function of a strongly interacting one-dimensional Bose gas in the Tonks-Girardeau regime, valid for any type of confining potential, and apply it to bosons on a lattice to obtain the full spectral function, at all energy and momentum scales. We find that it displays three main singularity lines. The first two can be identified as the analogs of Lieb-I and Lieb-II modes of a uniform fluid; the third one, instead, is specifically due to the presence of the lattice. We show that the spectral function displays a power-law behaviour close to the Lieb-I and Lieb-II singularities, as predicted by the non-linear Luttinger liquid description, and obtain the exact exponents. In particular, the Lieb-II mode shows a divergence in the spectral function, differently from what happens in the dynamical structure factor, thus providing a route to probe it in experiments with ultracold atoms.Comment: 10 pages, 3 figure

Parabolic Trough System Operating with Nanofluids: Comparison with the Conventional Working Fluids and Influence on the System Performance

Abstract To analyse the behaviour of a parabolic trough operating with nanofluids, and compare its performance to the more traditional ones using oil, a model for the thermal analysis of the system has been developed and implemented in Matlab. The simulations have been performed for a suspension of Al 2 O 3 in synthetic oil and its characteristics compared to the corresponding basic liquid used by itself. The string has been assumed to have a length of 100 m and a concentrating surface area of 550 m 2 . The simulations have been carried out for different DNI (Direct normal irradiance) and variable mass flow, ensuring a temperature at the collector outlet below 400C. For a proper comparison, the following variables and efficiency indicators have been checked: power output, pumping power, thermal efficiency and overall efficiency of the parabolic trough system

Spin-orbital polarization of Majorana edge states in oxides nanowires

We investigate a paradigmatic case of topological superconductivity in a one-dimensional nanowire with $d-$orbitals and a strong interplay of spin-orbital degrees of freedom due to the competition of orbital Rashba interaction, atomic spin-orbit coupling, and structural distortions. We demonstrate that the resulting electronic structure exhibits an orbital dependent magnetic anisotropy which affects the topological phase diagram and the character of the Majorana bound states (MBSs). The inspection of the electronic component of the MBSs reveals that the spin-orbital polarization generally occurs along the direction of the applied Zeeeman magnetic field, and transverse to the magnetic and orbital Rashba fields. The competition of symmetric and antisymmetric spin-orbit coupling remarkably leads to a misalignment of the spin and orbital moments transverse to the orbital Rashba fields, whose manifestation is essentially orbital dependent. The behavior of the spin-orbital polarization along the applied Zeeman field reflects the presence of multiple Fermi points with inequivalent orbital character in the normal state. Additionally, the response to variation of the electronic parameters related with the degree of spin-orbital entanglement leads to distinctive evolution of the spin-orbital polarization of the MBSs. These findings unveil novel paths to single-out hallmarks relevant for the experimental detection of MBSs.Comment: 14 pages, 8 figure

integration of an organic rankine cycle and a photovoltaic unit for micro scale chp applications in the residential sector

Abstract The purpose of this work is to analyse the performance of a novel system for combined heat and power (CHP) generation in small-scale applications. The system is based on an Organic Rankine Cycle (ORC) fed with biomass and a photovoltaic (PV) unit. The ORC and PV sub-systems operate in parallel to produce the required electrical energy. A preliminary investigation is performed to define the proper size of the photovoltaic unit. Afterwards, the analysis is focused on the hybrid system and a comparison between the two configurations is carried out. This work demonstrates the potential for integrating biomass and solar energy resources: during daylight, solar radiation is significant and the ORC system can be switched off or operated at partial load. Furthermore, the adoption of biomass makes it possible to overcome the intermittency of solar resource, increase the self-consumed electrical energy, and produce thermal energy, thereby saving natural gas for heating purposes

Exact Spectral Function of a Tonks-Girardeau Gas in a Lattice

The single-particle spectral function of a strongly correlated system is an essential ingredient to describe its dynamics and transport properties. We develop a method to evaluate exactly the spectral function for a gas of one-dimensional bosons with infinitely strong repulsions valid for any type of external confinement. Focusing on the case of a lattice confinement, we find that the spectral function displays three main singularity lines. One of them is due uniquely to lattice effects, while the two others correspond to the Lieb-I and Lieb-II modes occurring in a uniform fluid. Differently from the dynamical structure factor, in the spectral function the Lieb-II mode shows a divergence, thus providing a route to probe such mode in experiments with ultracold atoms

Emergence of anomalous dynamics from the underlying singular continuous spectrum in interacting many-body systems

We investigate the dynamical properties of an interacting many-body system with a nontrivial energy potential landscape that may induce a singular continuous single-particle energy spectrum. Focusing on the Aubry-Andre model, whose anomalous transport properties in the presence of interaction was recently demonstrated experimentally in an ultracold-gas setup, we discuss the anomalous slowing down of the dynamics it exhibits and show that it emerges from the singular-continuous nature of the single-particle excitation spectrum. Our study demonstrates that singular-continuous spectra can be found in interacting systems, unlike previously conjectured by treating the interactions in the mean-field approximation. This, in turns, also highlights the importance of the many-body correlations in giving rise to anomalous dynamics, which, in many-body systems, can result from a nontrivial interplay between geometry and interactions

Ballistic transport through quantum point contacts of multiorbital oxides

Linear and nonlinear transport properties through a quantum point contact based on oxides two-dimensional electron gas is examined using the tight-binding method and the k·p approach. The ballistic transport is analyzed in contacts realized at the (001) interface between band insulators LaAlO3 and SrTiO3 by using the Landauer-Büttiker method for many sub-bands derived from three Ti 3d orbitals (dyz, dzx, and dxy) in the presence of an out-of-plane magnetic field. We focus especially on the role played by the atomic spin-orbit coupling and the inversion-symmetry-breaking term. Three different transport regimes stem out: The first, at low energies, involving the first dxy-like sub-bands, where the conductance quantization is clearly observed; a second one, at intermediate energies, entailing further dxy-like sub-bands, where the sub-band splitting induced by the magnetic field is quenched; the third one, where the mixing between light dxy-like, heavy dyz-like, and dzx-like sub-bands is so strong that the conductance plateaus turn out to be very narrow. Very good agreement is found with recent experiments exploring the transport properties at low energies

Ballistic transport through quantum point contacts of multiorbital oxides

Linear and nonlinear transport properties through a quantum point contact based on oxides two-dimensional electron gas is examined using the tight-binding method and the k . p approach. The ballistic transport is analyzed in contacts realized at the (001) interface between band insulators LaAlO3 and SrTiO3 by using the Landauer-Buttiker method for many sub-bands derived from three Ti 3d orbitals (d(yz), d(zx), and d(xy) ) in the presence of an out-of-plane magnetic field. We focus especially on the role played by the atomic spin-orbit coupling and the inversion-symmetry-breaking term. Three different transport regimes stem out: The first, at low energies, involving the first d(xy)-like sub-bands, where the conductance quantization is clearly observed; a second one, at intermediate energies, entailing further d(xy)-like sub-bands, where the sub-band splitting induced by the magnetic field is quenched; the third one, where the mixing between light d(xy)-like, heavy d(yz)-like, and d(zx)-like sub-bands is so strong that the conductance plateaus turn out to be very narrow. Very good agreement is found with recent experiments exploring the transport properties at low energies

Emergence of anomalous dynamics from the underlying singular continuous spectrum in interacting many-body systems

We investigate the dynamical properties of an interacting many-body system with a nontrivial energy potential landscape that may induce a singular continuous single-particle energy spectrum. Focusing on the Aubry-Andre model, whose anomalous transport properties in the presence of interaction was recently demonstrated experimentally in an ultracold-gas setup, we discuss the anomalous slowing down of the dynamics it exhibits and show that it emerges from the singular-continuous nature of the single-particle excitation spectrum. Our study demonstrates that singular-continuous spectra can be found in interacting systems, unlike previously conjectured by treating the interactions in the mean-field approximation. This, in turns, also highlights the importance of the many-body correlations in giving rise to anomalous dynamics, which, in many-body systems, can result from a nontrivial interplay between geometry and interactions.Peer reviewe

Spin-orbital polarization of Majorana edge states in oxide nanowires

We investigate a paradigmatic case of topological superconductivity in a one-dimensional nanowire with d-orbitals and a strong interplay of spin-orbital degrees of freedom due to the competition of the orbital Rashba interaction, atomic spin-orbit coupling, and structural distortions. We demonstrate that the resulting electronic structure exhibits an orbital-dependent magnetic anisotropy which affects the topological phase diagram and the character of the Majorana bound states (MBSs). The inspection of the electronic component of the MBSs reveals that the spin-orbital polarization generally occurs along the direction of the applied Zeeman magnetic field, and transverse to the magnetic and orbital Rashba fields. The competition of symmetric and antisymmetric spin-orbit coupling remarkably leads to a misalignment of the spin and orbital moments transverse to the orbital Rashba fields, whose manifestation is essentially orbital dependent. The behavior of the spin-orbital polarization along the applied Zeeman field reflects the presence of multiple Fermi points with inequivalent orbital character in the normal state. Additionally, the spin and spatially resolved density of states leads to distinctive fingerprints of the topological phase, especially when comparing the character of the MBS with the energy excitation close to the gap edge. These findings unveil novel paths to single out hallmarks relevant for the experimental detection of MBSs