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73 records were found.

Temperature evolution of subharmonic gap structures in MgB$_2$/Nb point-contacts

We have performed point-contact spectroscopy experiments on superconducting micro-constrictions between Nb tips and high quality MgB2 pellets. We measured the temperature evolution (between 4.2 K and 300 K) of the current–voltage (I–V) and of the dynamical conductance (dI/dV–V) characteristics. Above the Nb critical temperature Click to view the MathML source, the conductance of the constrictions behaves as predicted by the BTK model for S/N contacts being Nb in its normal state below Click to view the MathML source, the contacts show Josephson current and subharmonic gap structures, due to multiple Andreev reflections. These observations clearly indicate the coupling of the MgB2 3D π-band with the Nb superconducting order parameter. We found Δπ = 2.4 ± 0.2 meV for the three-dimensional gap of MgB2.

Subharmonic gap structures and Josephson effect in MgB$_2$/Nb micro-constrictions

Superconducting micro-constrictions between Nb tips and high quality MgB$_{2}$ pellets have been realized by means of a point-contact inset, driven by a micrometric screw. Measurements of the current-voltage characteristics and of the dynamical conductance versus bias have been performed in the temperature range between 4.2 K and 50 K. Above the Nb critical temperature T$_{C}^{Nb}$, the conductance of the MgB$_2$/normal-metal constrictions behaves as predicted by the BTK model for low resistance contacts while high resistance junctions show quasiparticle tunneling characteristics. Consistently, from the whole set of data we infer the value $\Delta_{\pi} = 2.5 \pm 0.2$ meV for the three-dimensional gap of MgB$_2$. Below T$_{C}^{Nb}$, low resistance contacts show Josephson current and subharmonic gap structures (SGS), due to multiple And...

Analysing surface structures on (Ga,Mn)As by Atomic Force Microscopy

Comment: 5 pages, 2 figures, 2 tables. To appear in J. Nanosci. Nanotechnol. (special issue for the RTNSA conference 2011)

Critical Current Oscillations in Strong Ferromagnetic Pi-Junctions

Comment: 4 pages 3 figures 1 table. Revised version as accepted for publication. To appear in Physical Review Letters

Spin polarization of (Ga,Mn)As measured by Andreev Spectroscopy: The role of spin-active scattering

Comment: 4 pages, 3 figures

Surface morphology and magnetic anisotropy in (Ga,Mn)As

Comment: 3 pages, 4 figures, 1 table. Replaced with published version

General properties of the pion production reaction in nuclear matter

Comment: 23 pages, Latex, accepted for publication in Nucl. Phys. A

The pi -> pi pi process in nuclei and the restoration of chiral symmetry

Comment: accepted for publication in Nucl. Phys. A

Evidence for 6{\Lambda}H

Evidence for the neutron-rich hypernucleus 6{\Lambda}H is presented from the FINUDA experiment at DA{\Phi}NE, Frascati, studying ({\pi}+, {\pi}-) pairs in coincidence from the K- +6Li \rightarrow 6 H+{\pi}+ production reaction followed by 6{\Lambda}H \rightarrow 6He + {\pi}- weak decay. The production rate of 6{\Lambda}H undergoing this two-body {\pi}- decay is determined to be (2.9\pm2.0)\cdot10-6/K-. Its binding energy, evaluated jointly from production and decay, is B{\Lambda}(6{\Lambda}H) = (4.0\pm1.1) MeV with respect to 5H+{\Lambda}. A systematic difference of (0.98 \pm 0.74) MeV between B{\Lambda} values derived separately from decay and from production is tentatively assigned to the 6{\Lambda}H 0+g.s. \rightarrow 1+ excitation.

Study of some two-body non-mesonic decays of $^4_\Lambda$He and $^5_\Lambda$He

Comment: revised version, typos corrected, more figures inserted, more extended discussions in sections 3, 4. Errors in tab. 8 modified, yields + upper limits quoted. 16 pages, 8 figures, 2 tables