Heat transport through quantum Hall edge states: Tunneling versus capacitive coupling to reservoirs

We study the heat transport along an edge state of a two-dimensional electron gas in the quantum Hall regime, in contact to two reservoirs at different temperatures. We consider two exactly solvable models for the edge state coupled to the reservoirs. The first one corresponds to filling $\nu=1$ and tunneling coupling to the reservoirs. The second one corresponds to integer or fractional filling of the sequence $\nu=1/m$ (with $m$ odd), and capacitive coupling to the reservoirs. In both cases we solve the problem by means of non-equilibrium Green function formalism. We show that heat propagates chirally along the edge in the two setups. We identify two temperature regimes, defined by $\Delta$, the mean level spacing of the edge. At low temperatures, $T< \Delta$, finite size effects play an important role in heat transport, for both types of contacts. The nature of the contacts manifest themselves in different power laws for the thermal conductance as a function of the temperature. For capacitive couplings a highly non-universal behavior takes place, through a prefactor that depends on the length of the edge as well as on the coupling strengths and the filling fraction. For larger temperatures, $T>\Delta$, finite-size effects become irrelevant, but the heat transport strongly depends on the strength of the edge-reservoir interactions, in both cases. The thermal conductance for tunneling coupling grows linearly with $T$, whereas for the capacitive case it saturates to a value that depends on the coupling strengths and the filling factors of the edge and the contacts.Comment: 15 pages, 5 figure

Process parameter-growth environment-film property relationships for the sputter deposited yttrium-oxygen system

In this study, a Y target was sputtered in radio frequency (rf)‐excited, rare gas discharges (Ne, Ar) containing 0%–40% O_2, operated at cathode voltage from −1.0 to −1.7 kV. In situ optical emission spectrometry was used to monitor two neutral excited Y atom transitions (λ=0.6191, 0.6793 μm) and an excited O atom transition (λ=0.7774 μm) as a function of changing process parameter. Films were grown on fused SiO_2 substrates, and their crystallography, optical behavior, and electrical resistivity was determined. A "phase diagram" for Y–O not grown under conditions of equilibrium thermodynamics was constructed, and included hexagonal Y, cubic Y_2O_3, and Y and Y_2O_3 that had no long range crystallographic order. Two direct optical transitions across the energy band gap of cubic Y_2O_3, at 5.07 and 5.73 eV, were identified. Combining discharge diagnostics, growth rate, and film property results, it was concluded that Y_2O_3 was formed at the substrate concurrent with the complete oxidation of the target surface. Even after target oxidation, the discharge contained atomic Y. On the basis of fundamental optical absorption edge characteristics, cubic Y_2O_3 that more closely resembled the bulk material was obtained when the Y‐oxide molecule/Y atom flux to the substrate was high

Fermioni di Dirac nel grafene

In questo lavoro si affronta l'argomento dei fermioni di Dirac nel grafene, si procederà compiendo nel primo capitolo un'analisi alla struttura reticolare del materiale per poi ricostruirne, sfruttando l'approssimazione di tigth-binding, le funzioni d'onda delle particelle che vivono negli orbitali del carbonio sistemate nella struttura reticolare e ricavarne grazie al passaggio in seconda quantizzazione l'Hamiltoniana. Nel secondo capitolo si ricavano brevemente le equazioni di Dirac e dopo una piccola nota storica si discutono le equazioni di Weyl arrivando all'Hamiltoniana dei fermioni a massa nulla mostrando la palese uguaglianza alla relazione di dispersione delle particelle del grafene. Nel terzo capitolo si commentano le evidenze sperimentali ottenute dalla ASPEC in cui si manifesta per le basse energie uno spettro lineare, dando così conferma alla teoria esposta nei capitoli precedenti

An approach for estimating measurement uncertainty in medical laboratories using data from long-term quality control and external quality assessment schemes

The present study was prompted by the ISO 15189 requirements that medical laboratories should estimate measurement uncertainty (MU)

Extended Hubbard model with soft-shoulder interaction

Recenti studi riguardanti gli Atomi di Rydberg hanno mostrato che, tali sistemi realizzano una peculiare interazione che sembra essere attiva soltanto entro una distanza finita. A partire da questa osservazione negli ultimi anni sono stati svolti studi teorici e sperimentali volti a descrivere le peculiari caratteristiche di tali sistemi. Un’analisi particolarmente interessante `e stata fatta focalizzando su sistemi unidimensionali implementati con bosoni hard-core e fermioni spinless, da cui è stato osservato che dal diagramma di fase si distinguono tre fasi: una prima che sembra soddisfare il paradigma dei liquidi di Luttinger, una seconda che ricalca una struttura critallina, ed una terza che si comporta come un liquido di Luttinger di cluster. Dove per cluster sono intesi particolari aggregati di particelle che vengono a formarsi in funzione del rapporto tra il raggio di interazione e la densita’ di particelle nel sistema. In questo lavoro è stato esteso lo studio a sistemi a due specie fermioniche, cercando di osservare il diagramma di fase solo in un particolare caso limite della teoria definito “limite ad una specie”. Da questa analisi si è dimostrato che in questo limite la struttura del diagramma di fase sembra ricalcare perfettamente quanto visto per i casi precedenti, in pieno accordo con le attese teoriche

A new broad spectrum disinfectant suitable for the food industry

A unique biocide composition (patent pending) that is formed from a hydrogen peroxide and sodium hypochlorite mixture was investigated. A biocidal complex is formed by adding the peroxide to the hypochlorite in an amount so that the weight ratio of the peroxide to the hypochlorite is no less than 1:10. The chemical structure of this biocidal complex is uncertain but we postulate that it is a semi-stable complex, whose stability is disrupted by heat, acid, U/V exposure and the presence of organic matter (i.e., microbes) The antimicrobial activity of the biocidal complex is most likely a combination effect between oxidation and reductive mechanisms The biocidal complex needed from one sixth to one half the concentration of hydrogen peroxide and from one twentieth to one half that of sodium hypochlorite to kill a range of Gram-positive and Gram-negative cells. In the case of bacterial spores (Bacillus sp.), MICs of the biocidal complex ranged from one twentieth to one half and from one fourth to one half for hydrogen peroxide and sodium hypochlorite, respectively. FIC values for both bacterial cells and spores were less than one. FIC values of less than one indicate that a synergistic effect exists between biocide components. The activity of the biocide is stable at alkaline pH, with a half-life of at least 42 days. It is non-corrosive and can be effective in both a dip and spray mode against bacterial cells in their planktonic or sessile state. Our studies indicate that sodium hypochlorite is not only synergistic with hydrogen peroxide but with sodium peroxide as well The use of this biocidal complex may provide a safe, effective and easy method for killing potential pathogens as well as for disinfecting and removing biofilms, as they pose a threat to human safety, particularly in the Food Industry