Publications: Pre-prints
L. Barbiero, A. Montorsi and M. Roncaglia, Non local longe range orders in 1D fermionic systems,
pre-print ArXiv: 1302.6136
We prove on a prototype Hamiltonian that hidden long range order is always present in the gapped phases of interacting fermionic systems on one dimensional lattices. It is captured by correlation functions of appropriate nonlocal charge and/or spin operators, which remain asymptotically finite. The corresponding microscopic orders are classified. The results are confirmed by DMRG numerical simulation of the phase diagram of the extended Hubbard model, and of a Haldane insulator phase.
R. Rosati, F. Dolcini, R.C. Iotti, and F. Rossi, The Wigner-function formalism applied to semiconductor quantum devices: Failure of the conventional boundary condition scheme,
pre-print ArXiv: 1302.6136
The Wigner-function formalism is a widely used approach to model charge transport in semiconductor nanodevices. Primary goal of the present Paper is to point out and explain intrinsic limitations of the conventional quantum-device modeling based on such Wigner-function paradigm, providing a definite answer to open questions related to the application of the conventional spatial boundary condition scheme to the Wigner transport equation. Our analysis shows that (i) in the presence of a symmetric device potential the solution of the Wigner equation (compatible with given boundary conditions) is not unique, and (ii) also when the solution is unique, the latter is not necessarily a physical Wigner function, i.e., the Weyl-Wigner transform of a single-particle density matrix.
A. Fornieri, M. Amado, F. Carillo, F. Dolcini, G. Biasiol, L. Sorba, V. Pellegrini, and F. Giazotto, A ballistic quantum ring Josephson interferometer, pre-print ArXiv: 1211.1629
We report the realization of a ballistic Josephson interferometer. The interferometer is made by a quantum ring etched in a nanofabricated two-dimensional electron gas confined in an InAs-based heterostructure laterally contacted to superconducting niobium leads. The Josephson current flowing through the structure shows oscillations with h/e flux periodicity when threading the loop with a perpendicular magnetic field. This periodicity, in sharp contrast with the h/2e one observed in conventional dc superconducting quantum interference devices, confirms the ballistic nature of the device in agreement with theoretical predictions. This system paves the way for the implementation of interferometric Josephson pi-junctions, and for the investigation of Majorana fermions.