Optical properties of rare earth thin films

Measurements have been made of the complex refractive index of thin films of several of the rare earth elements in the photon energy range from 0,33 - 3.0eV, using a conventional ellipsometric method. The observations were carried out at various temperatures between 4.2 and 300ºK corresponding to the different magnetically ordered phases of the elements neodyraium, gadolinium, terbium, dysprosium, holmium, erbium and ytterbium. In the elements which show helical ordering, no evidence was found for absorption at the gaps corresponding to the superzone boundaries. Instead the results suggest that magnetic ordering of any type is seen in a general way through direct transitions between the exchange split levels of the band structure. The exchange energies estimated this way are in reasonable agreement with theoretical values. Suggested locations are given for the regions in k space corresponding to these "magnetic transitions". The Drude contribution to the optical conductivity has been obtained and the variation of σ(w)(_w=o) for the different elements is in good agreement with static conductivity measurements although the magnitude of the optical constant is in general larger by about 15%.This is presumably due to the effects of the joint anisotropy of the electron relaxation times and velocities at the Fermi surface

Selective Area Grown Semiconductor-Superconductor Hybrids: A Basis for Topological Networks

We introduce selective area grown hybrid InAs/Al nanowires based on molecular beam epitaxy, allowing arbitrary semiconductor-superconductor networks containing loops and branches. Transport reveals a hard induced gap and unpoisoned 2e-periodic Coulomb blockade, with temperature dependent 1e features in agreement with theory. Coulomb peak spacing in parallel magnetic field displays overshoot, indicating an oscillating discrete near-zero subgap state consistent with device length. Finally, we investigate a loop network, finding strong spin-orbit coupling and a coherence length of several microns. These results demonstrate the potential of this platform for scalable topological networks among other applications.Comment: NBI QDEV 201

B-meson production at forward and backward rapidity in p+p and Cu + Au collisions at √sNN=200 GeV

The fraction of J/psi mesons which come from B-meson decay, F-B -> J/psi is measured for J/psi rapidity 1.2 0 in p + p and Cu+Au collisions at root s(NN) = 200 GeV with the PHENIX detector. The extracted fraction is F-B -> J/psi = 0.025 +/- 0.006 (stat) +/- 0.010(syst) for p + p collisions. For Cu+Au collisions, F-B -> J/psi is 0.094 +/- 0.028(stat) +/- 0.037(syst) in the Au-going direction (-2.2 <y <-1.2) and 0.089 +/- 0.026(stat) +/- 0.040(syst) in the Cu-going direction (1.2 <y <2.2). The nuclear modification factor, R-CuAu,of B mesons in Cu+Au collisions is consistent with binary scaling of measured yields in p + p at both forward and backward rapidity.Peer reviewe

Cross section and transverse single-spin asymmetry of muons from open heavy-flavor decays in polarized p plus p collisions at root s=200 GeV

The cross section and transverse single-spin asymmetries of mu(-) and mu(+) from open heavy-flavor decays in polarized p + p collisions at pffisffiffi root s = 200 GeV were measured by the PHENIX experiment during 2012 at the Relativistic Heavy Ion Collider. Because heavy-flavor production is dominated by gluon-gluon interactions at ffiffiffi root s = 200 GeV, these measurements offer a unique opportunity to obtain information on the trigluon correlation functions. The measurements are performed at forward and backward rapidity (1.4 <vertical bar y vertical bar <2.0) over the transverse momentum range of 1.25 <p(T) <7 GeV/c for the cross section and 1.25 <p(T) <5 GeV/c for the asymmetry measurements. The obtained cross section is compared to a fixed-order-plus-next-to-leading-log perturbative-quantum-chromodynamics calculation. The asymmetry results are consistent with zero within uncertainties, and a model calculation based on twist-3 three-gluon correlations agrees with the data.Peer reviewe

Measurements of B -> J/psi at forward rapidity in p plus p collisions at root s=510 GeV

We report the first measurement of the fraction of J/psi mesons coming from B-meson decay (F (B -> J/psi)) in p + p collisions at root s = 510 GeV. The measurement is performed using the forward silicon vertex detector and central vertex detector at PHENIX, which provide precise tracking and distance-of-closest-approach determinations, enabling the statistical separation of J=. due to B-meson decays from prompt J/psi. The measured value of F (B -> J/psi) is 8.1% +/- 2.3% (stat) +/- 1.9% (syst) for J/psi with transverse momenta 0 J/psi) at PHENIX is compared to values measured by other experiments at higher center of mass energies and to fixed-order-next-toleading- logarithm and color-evaporation-model predictions. The b (b) over bar cross section per unit rapidity [d sigma/dy(pp -> b (b) over bar)] extracted from the obtained F (B -> J/psi) and the PHENIX inclusive J/psi cross section measured at 200 GeV scaled with color-evaporation-model calculations, at the mean B hadron rapidity y = +/- 1.7 in 510 GeV p + p collisions, is 3.63(-1.70)(+1.92) mu b. It is consistent with the fixed-order-next-toleading- logarithm calculations.Peer reviewe

Production of pi(0) and eta mesons in Cu plus Au collisions at root S-NN=200 GeV

Production of pi(0) and eta mesons has been measured at midrapidity in Cu+Au collisions at root S-NN = 200 GeV. Measurements were performed in pi(0) (eta) -> gamma gamma decay channel in the 1(2)-20 GeV/c transverse momentum range. A strong suppression is observed for pi(0) and eta meson production at high transverse momentum in central Cu+Au collisions relative to the p + p results scaled by the number of nucleon-nucleon collisions. In central collisions the suppression is similar to Au + Au with comparable nuclear overlap. The eta/pi(0) ratio measured as a function of transverse momentum is consistent with m(T)-scaling parametrization down to p(T) = 2 GeV/c, its asymptotic value is constant and consistent with Au + Au and p + p and does not show any significant dependence on collision centrality. Similar results were obtained in hadron-hadron, hadron-nucleus, and nucleus-nucleus collisions as well as in e(+)e(-) collisions in a range of collision energies root S-NN = 3-1800 GeV. This suggests that the quark-gluon-plasma medium produced in Cu+Cu collisions either does not affect the jet fragmentation into light mesons or it affects the pi(0) and eta the same way.Peer reviewe

Against the “nightmare of a mechanically determined universe”: Why Bohm was never a Bohmian

David Bohm has put forward the first deterministic interpretation of quantum physics, and for this he seems to be regarded as a champion of determinism by physicists (both his contemporaries and the supporters of his interpretation, the so-called “Bohmians”) as well as by historians of physics. The standard narrative is that he underwent a “conversion” from being a supporter of Bohr to being a staunch determinist, due to his interaction with Einstein and his commitment to Marxism. Here we show that Bohm actually upheld with continuity throughout his career some philosophical tenets that included a strong rejection of mechanistic determinism. As such, we conclude that Bohm was never a Bohmian and that his philosophical views have been largely misinterpreted

Spin-degeneracy breaking and parity transitions in three-terminal Josephson junctions

Harnessing spin and parity degrees of freedom is of fundamental importance for the realization of emergent quantum devices. Nanostructures embedded in superconductor--semiconductor hybrid materials offer novel and yet unexplored routes for addressing and manipulating fermionic modes. Here we spectroscopically probe the two-dimensional band structure of Andreev bound states in a phase-controlled hybrid three-terminal Josephson junction. Andreev bands reveal spin-degeneracy breaking, with level splitting in excess of 9 GHz, and zero-energy crossings associated to ground state fermion parity transitions, in agreement with theoretical predictions. Both effects occur without the need of external magnetic fields or sizable charging energies and are tuned locally by controlling superconducting phase differences. Our results highlight the potential of multiterminal hybrid devices for engineering quantum states

Zeeman and Orbital Driven Phase Transitions in Planar Josephson Junctions

We perform supercurrent and tunneling spectroscopy measurements on gate-tunable InAs/Al Josephson junctions (JJs) in an in-plane magnetic field, and report on phase shifts in the current-phase relation measured with respect to an absolute phase reference. The impact of orbital effects is investigated by studying multiple devices with different superconducting lead sizes. At low fields, we observe gate-dependent phase shifts of up to ${\varphi_{0}=0.5\pi}$ which are consistent with a Zeeman field coupling to highly-transmissive Andreev bound states via Rashba spin-orbit interaction. A distinct phase shift emerges at larger fields, concomitant with a switching current minimum and the closing and reopening of the superconducting gap. These signatures of an induced phase transition, which might resemble a topological transition, scale with the superconducting lead size, demonstrating the crucial role of orbital effects. Our results elucidate the interplay of Zeeman, spin-orbit and orbital effects in InAs/Al JJs, giving new understanding to phase transitions in hybrid JJs and their applications in quantum computing and superconducting electronics

Microwave-induced conductance replicas in hybrid Josephson junctions without Floquet-Andreev states

Light-matter interaction enables engineering of non-equilibrium quantum systems. In condensed matter, spatially and temporally cyclic Hamiltonians are expected to generate energy-periodic Floquet states, with properties inaccessible at thermal equilibrium. A recent work explored the tunnelling conductance of a planar Josephson junction under microwave irradiation, and interpreted replicas of conductance features as evidence of steady Floquet-Andreev states. Here we realise a similar device in a hybrid superconducting-semiconducting heterostructure, which utilises a tunnelling probe with gate-tunable transparency and allows simultaneous measurements of Andreev spectrum and current-phase relation of the planar Josephson junction. We show that, in our devices, spectral replicas in sub-gap conductance emerging under microwave irradiation are caused by photon assisted tunnelling of electrons into Andreev states. The current-phase relation under microwave irradiation is also explained by the interaction of Andreev states with microwave photons, without the need to invoke Floquet states. The techniques outlined in this study establish a baseline to distinguish photon assisted tunnelling from Floquet-Andreev states in mesoscopic devices, a crucial development towards understanding light-matter coupling in hybrid nanostructures