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Author Doğan, F.; Covaci, L.; Kim, W.; Marsiglio, F. doi  openurl
  Title Emerging nonequilibrium bound state in spin-current–local-spin scattering Type A1 Journal article
  Year (down) 2009 Publication Physical Review B Abbreviated Journal Phys Rev B  
  Volume 80 Issue 10 Pages 104434  
  Keywords A1 Journal article  
  Abstract Magnetization reversal is a well-studied problem with obvious applicability in computer hard drives. One can accomplish a magnetization reversal in at least one of two ways: application of a magnetic field or through a spin current. The latter is more amenable to a fully quantum-mechanical analysis. We formulate and solve the problem whereby a spin current interacts with a ferromagnetic Heisenberg spin chain, to eventually reverse the magnetization of the chain. Spin flips are accomplished through both elastic and inelastic scattering. A consequence of the inelastic-scattering channel, when it is no longer energetically possible, is the occurrence of a nonequilibrium bound state, which is an emergent property of the coupled local plus itinerant spin system. For certain definite parameter values the itinerant spin lingers near the local spins for some time, before eventually leaking out as an outwardly diffusing state. This phenomenon results in spin-flip dynamics and filtering properties for this type of system.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000270383100077 Publication Date 2009-09-25  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Additional Links  
  Impact Factor 3.836 Times cited Open Access  
  Notes Approved Most recent IF: 3.836; 2009 IF: 3.475  
  Call Number UA @ lucian @ Serial 4436  
Permanent link to this record
 
 
Author Covaci, L.; Berciu, M. doi  openurl
  Title Polaron formation in the presence of Rashba spin-orbit coupling: implications for spintronics Type A1 Journal article
  Year (down) 2009 Publication Physical Review Letters Abbreviated Journal Phys Rev Lett  
  Volume 102 Issue 18 Pages 186403  
  Keywords A1 Journal article  
  Abstract We study the effects of the Rashba spin-orbit coupling on polaron formation, using a suitable generalization of the momentum average approximation. While previous work on a parabolic band model found that spin-orbit coupling increases the effective mass, we show that the opposite holds for a tight-binding model, unless both the spin-orbit and the electron-phonon couplings are weak. It is thus possible to lower the effective mass of the polaron by increasing the spin-orbit coupling. We also show that when the spin-orbit coupling is large as compared to the phonon energy, the polaron retains only one of the spin-polarized bands in its coherent spectrum. This has major implications for the propagation of spin-polarized currents in such materials, and thus for spintronic applications.  
  Address Department of Physics, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z1  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Wos 000265948600049 Publication Date 2009-05-08  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0031-9007 ISBN Additional Links  
  Impact Factor 8.462 Times cited 25 Open Access  
  Notes Approved Most recent IF: 8.462; 2009 IF: 7.328  
  Call Number UA @ lucian @ Serial 4434  
Permanent link to this record
 
 
Author Marchand, D.; Covaci, L.; Berciu, M.; Franz, M. doi  openurl
  Title Giant proximity effect in a phase-fluctuating superconductor Type A1 Journal article
  Year (down) 2008 Publication Physical Review Letters Abbreviated Journal Phys Rev Lett  
  Volume 101 Issue 9 Pages 097004  
  Keywords A1 Journal article  
  Abstract When a tunneling barrier between two superconductors is formed by a normal material that would be a superconductor in the absence of phase fluctuations, the resulting Josephson effect can undergo an enormous enhancement. We establish this novel proximity effect by a general argument as well as a numerical simulation and argue that it may underlie recent experimental observations of the giant proximity effect between two cuprate superconductors separated by a barrier made of the same material rendered normal by severe underdoping.  
  Address Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada V6T 1Z1  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Wos 000259195800055 Publication Date 2008-08-28  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0031-9007 ISBN Additional Links  
  Impact Factor 8.462 Times cited 17 Open Access  
  Notes Approved Most recent IF: 8.462; 2008 IF: 7.180  
  Call Number UA @ lucian @ Serial 4433  
Permanent link to this record
 
 
Author Covaci, L.; Berciu, M. doi  openurl
  Title Survival of the Dirac points in rippled graphene Type A1 Journal article
  Year (down) 2008 Publication Physical Review Letters Abbreviated Journal Phys Rev Lett  
  Volume 100 Issue 25 Pages 256405  
  Keywords A1 Journal article; Electron Microscopy for Materials Science (EMAT);  
  Abstract We study the effects of the rippling of a graphene sheet on quasiparticle dispersion. This is achieved using a generalization to the honeycomb lattice of the momentum average approximation, which is accurate for all coupling strengths and at all energies. We show that even though the position of the Dirac points may move and the Fermi speed can be renormalized significantly, quasiparticles with very long lifetimes survive near the Dirac points even for very strong couplings.  
  Address Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z1  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language English Wos 000257230500047 Publication Date 2008-06-26  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0031-9007 ISBN Additional Links  
  Impact Factor 8.462 Times cited 15 Open Access  
  Notes Approved Most recent IF: 8.462; 2008 IF: 7.180  
  Call Number UA @ lucian @ Serial 4010  
Permanent link to this record
 
 
Author Covaci, L.; Berciu, M. doi  openurl
  Title Holstein polaron: The effect of coupling to multiple-phonon modes Type A1 Journal article
  Year (down) 2007 Publication Epl Abbreviated Journal Epl-Europhys Lett  
  Volume 80 Issue 6 Pages 67001  
  Keywords A1 Journal article  
  Abstract We investigate the effects of coupling to multiple-phonon modes on the properties of a Holstein polaron. To this end, we generalize the Momentum Average approximations MA((0)) and MA((1)) to deal with multiple-phonon modes. As for a single-phonon mode, these approximations are found to be numerically very efficient. They become exact for very weak or very strong couplings, and are highly accurate in the intermediate regimes, e.g. the spectral weights obey exactly the first six, respectively eight, sum rules. Our results show that the effect on ground-state properties is cumulative in nature. As a result, if the effective coupling to one mode is much larger than to all the others, this mode effectively determines the ground-state properties. However, even very weak coupling to a second phonon mode has important non-perturbational effects on the higher-energy spectrum, in particular on the dispersion and the phonon statistics of the polaron band. This has important consequences on the analysis and interpretation of data for real materials.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000251648300016 Publication Date 2007-11-30  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0295-5075 ISBN Additional Links  
  Impact Factor 1.957 Times cited 9 Open Access  
  Notes Approved Most recent IF: 1.957; 2007 IF: 2.206  
  Call Number UA @ lucian @ Serial 4431  
Permanent link to this record
 
 
Author Kim, W.; Covaci, L.; Dogan, F.; Marsiglio, F. doi  openurl
  Title Quantum mechanics of spin transfer in coupled electron-spin chains Type A1 Journal article
  Year (down) 2007 Publication Epl Abbreviated Journal Epl-Europhys Lett  
  Volume 79 Issue 6 Pages 67004  
  Keywords A1 Journal article  
  Abstract The manner in which spin-polarized electrons interact with a magnetized thin film is currently described by a semi-classical approach. This in turn provides our present understanding of the spin transfer, or spin torque phenomenon. However, spin is an intrinsically quantum-mechanical quantity. Here, we make the first strides towards a fully quantum-mechanical description of spin transfer through spin currents interacting with a Heisenberg-coupled spin chain. Because of quantum entanglement, this requires a formalism based on the density matrix approach. Our description illustrates how individual spins in the chain time-evolve as a result of spin transfer.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000250409500023 Publication Date 2007-08-24  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 0295-5075 ISBN Additional Links  
  Impact Factor 1.957 Times cited 3 Open Access  
  Notes Approved Most recent IF: 1.957; 2007 IF: 2.206  
  Call Number UA @ lucian @ Serial 4430  
Permanent link to this record
 
 
Author Kim, W.; Covaci, L.; Marsiglio, F. doi  openurl
  Title Impurity scattering of wave packets on a lattice Type A1 Journal article
  Year (down) 2006 Publication Physical Review B Abbreviated Journal Phys Rev B  
  Volume 74 Issue 20 Pages 205120  
  Keywords A1 Journal article  
  Abstract Quantum transport in a lattice is distinct from its counterpart in continuum media. Even a free wave packet travels differently in a lattice than in the continuum. We describe quantum scattering in a one-dimensional lattice and illustrate characteristics of quantum transport such as resonant transmission. In particular we examine the transport characteristics of a random trimer model. We demonstrate the real-time propagation of a wave packet and its phase shift due to impurity configurations. Spin-flip scattering is also taken into account in a spin-chain system. We show how individual spins in the chain evolve as a result of a spin-flip interaction between an incoming electron and a spin chain.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000242409400030 Publication Date 2006-11-27  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Additional Links  
  Impact Factor 3.836 Times cited 14 Open Access  
  Notes Approved Most recent IF: 3.836; 2006 IF: 3.107  
  Call Number UA @ lucian @ Serial 4428  
Permanent link to this record
 
 
Author Kim, W.; Covaci, L.; Marsiglio, F. doi  openurl
  Title Hidden symmetries of electronic transport in a disordered one-dimensional lattice Type A1 Journal article
  Year (down) 2006 Publication Physical Review B Abbreviated Journal Phys Rev B  
  Volume 73 Issue 19 Pages 195109  
  Keywords A1 Journal article  
  Abstract Correlated, or extended, impurities play an important role in the transport properties of dirty metals. Here, we examine, in the framework of a tight-binding lattice, the transmission of a single electron through an array of correlated impurities. In particular we show that particles transmit through an impurity array in identical fashion, regardless of the direction of traversal. The demonstration of this fact is straightforward in the continuum limit, but requires a detailed proof for the discrete lattice. We also briefly demonstrate and discuss the time evolution of these scattering states, to delineate regions (in time and space) where the aforementioned symmetry is violated.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000237950400042 Publication Date 2006-05-11  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Additional Links  
  Impact Factor 3.836 Times cited 5 Open Access  
  Notes Approved Most recent IF: 3.836; 2006 IF: 3.107  
  Call Number UA @ lucian @ Serial 4429  
Permanent link to this record
 
 
Author Covaci, L.; Marsiglio, F. doi  openurl
  Title Proximity effect and Josephson current in clean strong/weak/strong superconducting trilayers Type A1 Journal article
  Year (down) 2006 Publication Physical Review B Abbreviated Journal Phys Rev B  
  Volume 73 Issue 1 Pages 014503  
  Keywords A1 Journal article  
  Abstract Recent measurements of the Josephson critical current through LSCO/LCO/LSCO thin films showed an unusually large proximity effect. Using the Bogoliubov-de Gennes equations for a tight-binding Hamiltonian we describe the proximity effect in weak links between a superconductor with critical temperature T-c and one with critical temperature T-c('), where T-c > T-c('). The weak link (N-') is therefore a superconductor above its own critical temperature and the superconducting regions are considered to have either s-wave or d-wave symmetry. We note that the proximity effect is enhanced due to the presence of superconducting correlations in the weak link. The dc Josephson current is calculated, and we obtain a nonzero value for temperatures greater than T-c(') for sizes of the weak links that can be almost an order of magnitude greater than the conventional coherence length. Considering pockets of superconductivity in the N-' layer, we show that this can lead to an even larger effect on the Josephson critical current by effectively shortening the weak link.  
  Address  
  Corporate Author Thesis  
  Publisher Place of Publication Editor  
  Language Wos 000235009000103 Publication Date 2006-01-03  
  Series Editor Series Title Abbreviated Series Title  
  Series Volume Series Issue Edition  
  ISSN 1098-0121 ISBN Additional Links  
  Impact Factor 3.836 Times cited 31 Open Access  
  Notes Approved Most recent IF: 3.836; 2006 IF: 3.107  
  Call Number UA @ lucian @ Serial 4427  
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