Bare Reggeons in asymptotic free theories

Conformal symmetry is used to investigate the Regge asymptotics for the six dimensional scalar φ³ model and the QCD vacuum exchange amplitude. Resulting angular momentum cuts change into series of poles by scale breaking due to renormalization. The Regge pole trajectories are calculated for large momentum transfer.     

57Fe,119Sn and151Eu Mössbauer study of EuBa2(Cu1−x−y 119Sn x 57Fe y )3O7−δ superconductor

¹⁵¹Eu,¹¹⁹Sn and⁵⁷Fe Mössbauer spectroscopy was used to study a EuBa₂(Cu_1?x?y Sn _x Fe _v )₃O_7?δ superconductor in which sites were replaced by all three Mössbauer isotopes in the same sample in order to get information about the site preferences and structural changes. We have found changes in the Mössbauer parameters of the⁵⁷Fe,¹¹⁹Sn and¹⁵¹Eu spectra compared to those recorded in the separately substituted EuBa₂Cu₃O_7?δ, EuBa₂(Cu_1?x Sn _x )₃O_7?δ, YBaCu_3?x Fe _x O_7?δ YBaCu_3?x Sn _x O_7?δ materials. These results can be interpreted as a consequence of the site preferences and the changes in the structure due to the presence of other additional substitutional elements.     

The electronic properties of Co nanowires on Cu(110)-p(2 × 3)N

We present the first measurements of the differential conductance of Co wires grown on top of Cu(110)-p(2 × 3)N (Cu₃N). We apply scanning tunneling spectroscopy (STS) in constant height and constant current mode to access the electronic density of states of the sample over a wide energy range. All measurements have been performed at 7 K. Our study reveals that the differential conductance of the Co wires is very similar to that of Cu₃N. Spectra of the differential conductance measured on the Co wires and on Cu₃N reveal that both systems exhibit the same characteristic features near + 1.8V and + 3.5 V.     

Ultrafast optical spin injection into image-potential states of Cu(001)

We report the observation of a net spin polarization in the n=1 image-potential state at the Cu(001) surface. The spin polarization is achieved by spin-selective multiphoton excitation of electrons from the spin-orbit split Cu d bands to the image-potential state using circularly polarized ultrafast light pulses. We show that by tuning the exciting photon energy, we can adjust the resonant coupling of the image-potential state to d bands of different double-group symmetry. This allows us to tune the spin polarization injected into the image-potential state.     

Structural secrets of multiferroic interfaces

We present an experimental and theoretical study of the geometric structure of ultrathin BaTiO(3) films grown on Fe(001). Surface x-ray diffraction reveals that the films are terminated by a BaO layer, while the TiO(2) layer is next to the top Fe layer. Cations in termination layers have incomplete oxygen shells inducing strong vertical relaxations. Onset of polarization is observed at a minimum thickness of two unit cells. Our findings are supported by first-principles calculations providing a quantitative insight into the multiferroic properties on the atomic scale.