Emergence of bound states in ballistic magnetotransport of graphene antidots

An experimental method for detection of bound states around an antidot formed from a hole in a graphene sheet is proposed by measuring the ballistic two terminal conductances. In particularly, we consider the effect of bound states formed by magnetic field on the two terminal conductance and show that one can observe Breit-Wigner like resonances in the conductance as a function of the Fermi level close to the energies of the bound states. In addition, we develop a new numerical method in which the computational effort is proportional to the linear dimensions, instead of the area of the scattering region beeing typical for the existing numerical recursive Green's function method.Comment: 7 pages, 6 figure

Local electrical tuning of the nonlocal signals in a Cooper pair splitter

A Cooper pair splitter consists of a central superconducting contact, S, from which electrons are injected into two parallel, spatially separated quantum dots (QDs). This geometry and electron interactions can lead to correlated electrical currents due to the spatial separation of spin-singlet Cooper pairs from S. We present experiments on such a device with a series of bottom gates, which allows for spatially resolved tuning of the tunnel couplings between the QDs and the electrical contacts and between the QDs. Our main findings are gate-induced transitions between positive conductance correlation in the QDs due to Cooper pair splitting and negative correlations due to QD dynamics. Using a semi-classical rate equation model we show that the experimental findings are consistent with in-situ electrical tuning of the local and nonlocal quantum transport processes. In particular, we illustrate how the competition between Cooper pair splitting and local processes can be optimized in such hybrid nanostructures.Comment: 9 pages, 6 figures, 2 table

Atomic size oscillations in conductance histograms for gold nanowires and the influence of work hardening

Nanowires of different nature have been shown to self-assemble as a function of stress at the contact between two macroscopic metallic leads. Here we demonstrate for gold wires that the balance between various metastable nanowire configurations is influenced by the microstructure of the starting materials and we discover a new set of periodic structures, which we interpret as due to the atomic discreteness of the contact size for the three principal crystal orientations.Comment: This version corrects an error in attributing the three observed periods, and includes a comparison with recent model calculation

Nanoscale spin-polarization in dilute magnetic semiconductor (In,Mn)Sb

Results of point contact Andreev reflection (PCAR) experiments on (In,Mn)Sb are presented and analyzed in terms of current models of charge conversion at a superconductor-ferromagnet interface. We investigate the influence of surface transparency, and study the crossover from ballistic to diffusive transport regime as contact size is varied. Application of a Nb tip to a (In,Mn)Sb sample with Curie temperature Tc of 5.4 K allowed the determination of spin-polarization when the ferromagnetic phase transition temperature is crossed. We find a striking difference between the temperature dependence of the local spin polarization and of the macroscopic magnetization, and demonstrate that nanoscale clusters with magnetization close to the saturated value are present even well above the magnetic phase transition temperature.Comment: 4 page

Roper excitation in p⃗+α→p⃗+α+X\vec{p}+\alpha \to \vec{p}+\alpha+X reactions

We calculate differential cross sections and the spin transfer coefficient $D_{nn}$ in the $\vec{p}+\alpha \to \vec{p}+\alpha+\pi^0$ reaction for proton bombarding energies from 1 to 10 GeV and $\pi^0 - p$ invariant masses spanning the region of the N$^*$(1440) Roper resonance. Two processes -- $\Delta$ excitation in the $\alpha$-particle and Roper excitation in the proton -- are included in an effective reaction model which was shown previously to reproduce existing inclusive spectra. The present calculations demonstrate that these two contributions can be clearly distinguished via $D_{nn}$, even under kinematic conditions where cross sections alone exhibit no clear peak structure due to the excitation of the Roper.Comment: 12 pages, 11 ps figures, Late

Magnetic field tuning and quantum interference in a Cooper pair splitter

Cooper pair splitting (CPS) is a process in which the electrons of naturally occurring spin-singlet pairs in a superconductor are spatially separated using two quantum dots. Here we investigate the evolution of the conductance correlations in an InAs CPS device in the presence of an external magnetic field. In our experiments the gate dependence of the signal that depends on both quantum dots continuously evolves from a slightly asymmetric Lorentzian to a strongly asymmetric Fano-type resonance with increasing field. These experiments can be understood in a simple three - site model, which shows that the nonlocal CPS leads to symmetric line shapes, while the local transport processes can exhibit an asymmetric shape due to quantum interference. These findings demonstrate that the electrons from a Cooper pair splitter can propagate coherently after their emission from the superconductor and how a magnetic field can be used to optimize the performance of a CPS device. In addition, the model calculations suggest that the estimate of the CPS efficiency in the experiments is a lower bound for the actual efficiency.Comment: 5 pages + 4 pages supplementary informatio

An Analysis of Musculoskeletal Variables, Comparative to Team Norms, Leading to an ACL Rupture

Please refer to the pdf version of the abstract located adjacent to the title

Pressure dependence of the spin gap in BaVS_3

We carried out magnetotransport experiments under hydrostatic pressure in order to study the nature of the metal-insulator transition in BaVS$_3$. Scaling relations for $\rho(T,H,p)$ are established and the pressure dependence of the spin gap is determined. Our new results, in conjunction with a re-analysis of earlier specific heat and susceptibility data, demonstrate that the transition is weakly second order. The nature of the phase diagram in the $T$--$p$--$H$ space is discussed.Comment: 5 pages, 5 figures, submitted to PRB Rap. Co