Phase transition in a chain of quantum vortices

We consider interacting vortices in a quasi-one-dimensional array of Josephson junctions with small capacitance. If the charging energy of a junction is of the order of the Josephson energy, the fluctuations of the superconducting order parameter in the system are considerable, and the vortices behave as quantum particles. Their density may be tuned by an external magnetic field, and therefore one can control the commensurability of the one-dimensional vortex lattice with the lattice of Josephson junctions. We show that the interplay between the quantum nature of a vortex, and the long-range interaction between the vortices leads to the existence of a specific commensurate-incommensurate transition in a one-dimensional vortex lattice. In the commensurate phase an elementary excitation is a soliton, with energy separated from the ground state by a finite gap. This gap vanishes in the incommensurate phase. Each soliton carries a fraction of a flux quantum; the propagation of solitons leads to a finite resistance of the array. We find the dependence of the resistance activation energy on the magnetic field and parameters of the Josephson array. This energy consists of the above-mentioned gap, and also of a boundary pinning term, which is different in the commensurate and incommensurate phases. The developed theory allows us to explain quantitatively the available experimental data.Comment: 14 pages, 7 eps figure

Orbital Kondo effect in carbon nanotubes

Progress in the fabrication of nanometer-scale electronic devices is opening new opportunities to uncover the deepest aspects of the Kondo effect, one of the paradigmatic phenomena in the physics of strongly correlated electrons. Artificial single-impurity Kondo systems have been realized in various nanostructures, including semiconductor quantum dots, carbon nanotubes and individual molecules. The Kondo effect is usually regarded as a spin-related phenomenon, namely the coherent exchange of the spin between a localized state and a Fermi sea of electrons. In principle, however, the role of the spin could be replaced by other degrees of freedom, such as an orbital quantum number. Here we demonstrate that the unique electronic structure of carbon nanotubes enables the observation of a purely orbital Kondo effect. We use a magnetic field to tune spin-polarized states into orbital degeneracy and conclude that the orbital quantum number is conserved during tunneling. When orbital and spin degeneracies are simultaneously present, we observe a strongly enhanced Kondo effect, with a multiple splitting of the Kondo resonance at finite field and predicted to obey a so-called SU(4) symmetry.Comment: 26 pages, including 4+2 figure

PENGARUH RETURN ON EQUITY, CURRENT RATIO, DEBT TO EQUITY RATIO, DAN EARNINGS PER SHARE TERHADAP HARGA SAHAM DENGAN INFLASI SEBAGAI VARIABEL MODERASI PADA PERUSAHAAN YANG TERDAFTAR DI JAKARTA ISLAMIC INDEX PERIODE 2015-2020

This study aims to analyze the effect of ROE, CR, DER, and EPS on stock prices with inflation as moderating in companies listed in JII for the 2015-2020 period. The sample of this research is 12 companies registered in JII that meet certain criteria with purposive sampling method and there are 72 observational data. This study uses panel data regression analysis techniques and moderated regression analysis techniques which are processed using Eviews 10. The results show that ROE and EPS have a significant positive effect on stock prices, while CR and DER have no effect on stock prices. Inflation is able to moderate the effect of ROE and DER on stock prices, but inflation cannot moderate the effect of CR and EPS on stock prices