Wess–Zumino supersymmetric phase and superconductivity in graphene

AbstractSupersymmetry is expected to exist in nature at high energies, but must be spontaneously broken at ordinary energy scales. The required energy scale in elementary particle physics is currently inaccessible, but condensed matter could furnish low energy realizations of supersymmetry. In graphene, electrons behave as ‘relativistic’ massless fermions in 1+2 dimensions. Here we propose phenomenologically, assuming that some microscopic parameters can be fine-tuned in graphene, the existence of a supersymmetric Wess–Zumino phase. The supersymmetry breaking leads to a superconductor phase, described by a relativistic Ginzburg–Landau phenomenology

Lanczos Calculation For The S=1/2 Antiferromagnetic Heisenberg Chain Up To N=28 Spins

Highly precise numerical calculations using a variation of the Lanczos method devised by Paige were performed for s=1/2 antiferromagnetic Heisenberg finite chains up to sizes N=28. Several interesting physical quantities, including the ground-state energy, the mass gap, and the spin-wave velocity, were computed and fitted for logarithmic finite-size corrections, as suggested by conformal invariance and Bethe ansatz calculations. A crossover size for a maximum of the spin-wave velocity is predicted for N50, well above the current available sizes in a typical Lanczos simulation. A list of our numerical results is given along with extrapolated values using standard algorithms. © 1991 The American Physical Society.4343703370

Magnetization, Spin Current, And Spin-transfer Torque From Su (2) Local Gauge Invariance Of The Nonrelativistic Pauli-schrödinger Theory

In this Brief Report, we consider local gauge symmetries of the nonrelativistic Pauli-Schrödinger theory. From the simplest free Lagrangian density for Pauli two-component spinors, we obtain the spin interaction with a magnetic field and define the spin-current vector without invoking relativistic theory. Applying U (1) ×SU (2) local gauge symmetry, and proceeding via the Noether's theorem, we are able to construct a covariant conserved spin-current density in a natural way. Our approach allow us to understand the main features of spin transport properties and suggests that SU (2) is a fundamental symmetry of nonrelativistic quantum mechanics. © 2008 The American Physical Society.781Wolf, S.A., Awschalom, D.D., Buhrman, R.A., Daughton, J.M., Von Molnar, S., Roukes, M.L., Chtchelkanova, A.Y., Treger, D.M., (2001) Science, 294, p. 1488. , SCIEAS 0036-8075 10.1126/science.1065389Zutic, I., Fabian, J., Das Sarma, S., (2004) Rev. Mod. Phys., 76, p. 323. , RMPHAT 0034-6861 10.1103/RevModPhys.76.323Zhang, S., Levy, P.M., Marley, A.C., Parkin, S.S.P., (1997) Phys. Rev. Lett., 79, p. 3744. , See, for instance, PRLTAO 0031-9007 10.1103/PhysRevLett.79.3744Dartora, C.A., Cabrera, G.G., (2004) J. Appl. Phys., 95, p. 6058. , JAPIAU 0021-8979 10.1063/1.1703825Dartora, C.A., Cabrera, G.G., (2005) Phys. Rev. B, 72, p. 064456. , PRBMDO 0163-1829 10.1103/PhysRevB.72.064456Petit, S., Baraduc, C., Thirion, C., Ebels, U., Liu, Y., Li, M., Wang, P., Dieny, B., (2007) Phys. Rev. Lett., 98, p. 077203. , PRLTAO 0031-9007 10.1103/PhysRevLett.98.077203Berger, L., (1996) Phys. Rev. B, 54, p. 9353. , PRBMDO 0163-1829 10.1103/PhysRevB.54.9353Slonczewski, J., (1996) J. Magn. Magn. Mater., 159, p. 1. , JMMMDC 0304-8853 10.1016/0304-8853(96)00062-5Murakami, S., Nagaosa, N., Zhang, S.-C., (2003) Science, 301, p. 1348. , SCIEAS 0036-8075 10.1126/science.1087128Murakami, S., Nagaosa, N., Zhang, S.-C., (2004) Phys. Rev. B, 69, p. 235206. , PRBMDO 0163-1829 10.1103/PhysRevB.69.235206Jiang, Z.F., Li, R.D., Zhang, S.-C., Liu, W.M., (2005) Phys. Rev. B, 72, p. 045201. , PRBMDO 0163-1829 10.1103/PhysRevB.72.045201Sinova, J., Culcer, D., Niu, Q., Sinitsyn, N.A., Jungwirth, T., MacDonald, A.H., (2004) Phys. Rev. Lett., 92, p. 126603. , PRLTAO 0031-9007 10.1103/PhysRevLett.92.126603Shen, S.Q., Ma, M., Xie, X.C., Zhang, F.C., (2004) Phys. Rev. Lett., 92, p. 256603. , PRLTAO 0031-9007 10.1103/PhysRevLett.92.256603Barnes, S.E., Maekawa, S., (2007) Phys. Rev. Lett., 98, p. 246601. , PRLTAO 0031-9007 10.1103/PhysRevLett.98.246601Hirsch, J.E., (1990) Phys. Rev. B, 42, p. 4774. , PRBMDO 0163-1829 10.1103/PhysRevB.42.4774Meier, F., Loss, D., (2003) Phys. Rev. Lett., 90, p. 167204. , PRLTAO 0031-9007 10.1103/PhysRevLett.90.167204Schutz, F., Kollar, M., Kopietz, P., (2003) Phys. Rev. Lett., 91, p. 017205. , PRLTAO 0031-9007 10.1103/PhysRevLett.91.017205Sun, Q.-F., Guo, H., Wang, J., (2004) Phys. Rev. B, 69, p. 054409. , PRBMDO 0163-1829 10.1103/PhysRevB.69.054409Vernes, A., Gyorffy, B.L., Weinberger, P., (2007) Phys. Rev. B, 76, p. 012408. , PRBMDO 0163-1829 10.1103/PhysRevB.76.012408Sakurai, J.J., (1994) Advanced Quantum Mechanics, , Revised ed. (Addison-Wesley, Reading, MABjorken, J.D., Drell, S.D., (1964) Relativistic Quantum Mechanics, , McGraw-Hill, New YorkGreiner, W., Reinhardt, J., (2002) Quantum Electrodynamics, , 3rd ed. (Springer-Verlag, BerlinWang, Y., Xia, K., Su, Z.B., Ma, Z., (2006) Phys. Rev. Lett., 96, p. 066601. , PRLTAO 0031-9007 10.1103/PhysRevLett.96.066601Sun, Q.F., Xie, X.C., (2005) Phys. Rev. B, 72, p. 245305. , PRBMDO 0163-1829 10.1103/PhysRevB.72.245305Fröhlich, J., Studer, U.M., (1992) Commun. Math. Phys., 148, p. 553. , CMPHAY 0010-3616 10.1007/BF02096549Fröhlich, J., Studer, U.M., (1992) Int. J. Mod. Phys. B, 6, p. 2201. , IJPBEV 0217-9792 10.1142/S0217979292001092Fröhlich, J., Studer, U.M., (1993) Rev. Mod. Phys., 65, p. 733. , RMPHAT 0034-6861 10.1103/RevModPhys.65.733Yang, C.N., Mills, R.L., (1954) Phys. Rev., 96, p. 191. , PHRVAO 0031-899X 10.1103/PhysRev.96.191Weinberg, S., (1996) The Quantum Teory of Fields, 1-2. , Cambridge University Press, CambridgeRyder, L.H., (1996) Quantum Field Theory, , 2nd ed. (Cambridge University Press, CambridgeLove, P.J., Boghosian, B.M., (2004) Physica a, 332, p. 47. , PHYADX 0378-4371 10.1016/j.physa.2003.09.055Wiese, U.-J., (2005) Nucl. Phys. B, Proc. Suppl., 141, p. 143. , 0920-5632Watts, S.M., Grollier, J., Van Der Wal, C.H., Van Wees, B.J., (2006) Phys. Rev. Lett., 96, p. 077201. , PRLTAO 0031-9007 10.1103/PhysRevLett.96.07720

Transverse Dynamic Susceptibility For An Ising Spin System: An Exact Eigenvalue Equation For The Resonance Frequencies

The dynamics of an Ising system is studied assuming that a microwave radiation field is coupled to the magnetic system through the transverse spin components. The transverse dynamic susceptibility is calculated with the use of the Green-function formalism in an exact manner, without the use of any decoupling scheme. The method yields an exact eigenvalue equation for the resonance frequencies, valid for any dimension and lattice, and a physical meaning of these resonances can be given in terms of the low-lying excitations for an Ising system. Those excitations correspond to spin-flip transitions in elementary clusters which represent all the possible spin arrangements of nearest neighbors. The present method does not allow for a calculation of line intensities without the help of statistical mechanics to evaluate correlation functions. © 1984 The American Physical Society.29143343

Extended Hubbard Model: A Cluster Effective-medium Approach

We present a cluster effective-medium approach to the extended Hubbard model, for the zero-temperature, half-filled-band paramagnetic phase. We recover the known limits and comment on the broadening corrections to the model, and find a first-order metal-insulator transition, resulting from both the cluster nature of the method and the correlated hopping term. © 1993 The American Physical Society.4719124451245

Universality Of Finite-size Scaling: Role Of The Boundary Conditions

The influence of the boundary conditions on the finite-size dependence of the mass gap in the 1D Ising model with a transverse field is studied by means of combined exact results and large-size numerical calculations. The well-known exponential form (for transverse fields smaller than the critical one) is only recovered in a limited range of parameters. A power-law behavior for the mass gap is even found in the case of antiperiodic boundary conditions. © 1986 The American Physical Society.57439339

Density Of States Of A Semi-infinite Rare-earth Metal With Magnetic Structure: A Simple Model

Using a simple tight-binding model and the transfer matrix approach, we have calculated the spectral density of states (SDOS) of a rare-earth metal in the presence of a surface for different magnetic arrangements (such as ferromagnetic, antiferromagnetic, and conical orderings). The local density of states (LDOS) has also been calculated for some examples, integrating the SDOS over the Brillouin zone. The main effect observed deals with the absence of Van Hove's singularities in the surface LDOS, a fact that appears to be an intrinsic property of the surface. Finally the relaxation of the overlap parameters at the surface is discussed and some numerical examples are shown. © 1979 The American Physical Society.2062269227

U(1)×su(2) Gauge Invariance Leading To Charge And Spin Conductivity Of Dirac Fermions In Graphene

Gauge symmetries have been identified in graphene and associated with specific physical properties. For instance, the U(1) gauge group is related to electrodynamics in (1+2)-dimensional [(1+2)D] space-time and non-Abelian gauge groups can describe curvature and torsion. Here we demonstrate that the Dirac Lagrangian for massless electrons near the Dirac points is also invariant under the group SU(2) related to local spin rotations, leading to the correct spin-orbit interactions and a rigorous definition for the spin-current density. Furthermore, we computed the charge and spin conductivity within the framework of Kubo linear response theory, using the algebra of relativistic Dirac spinors in (1+2)D space-time. The minimal value of electrical conductivity is predicted to be πq2/h, in agreement with typical experimental findings. © 2013 American Physical Society.8716Wallace, P.R., (1947) Phys. Rev., 71, p. 622. , PHRVAO 0031-899X 10.1103/PhysRev.71.622McLure, J.W., (1957) Phys. 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Phys., 83, p. 407. , RMPHAT 0034-6861 10.1103/RevModPhys.83.407Novoselov, K.S., Geim, A.K., Morozov, S.V., Jiang, D., Katsnelson, M.I., Grigorieva, I.V., Dubonos, S.V., Firsov, A.A., Two-dimensional gas of massless Dirac fermions in graphene (2005) Nature, 438 (7065), pp. 197-200. , DOI 10.1038/nature04233, PII N04233Zhang, Y., Tan, Y.-W., Stormer, H.L., Kim, P., Experimental observation of the quantum Hall effect and Berry's phase in graphene (2005) Nature, 438 (7065), pp. 201-204. , DOI 10.1038/nature04235, PII N04235McCreary, K.M., (2012) Phys. Rev. Lett., 109, p. 186604. , PRLTAO 0031-9007 10.1103/PhysRevLett.109.186604Mecklenburg, M., Regan, B.C., (2011) Phys. Rev. Lett., 106, p. 116803. , PRLTAO 0031-9007 10.1103/PhysRevLett.106.116803Abanin, D.A., (2011) Phys. Rev. Lett., 107, p. 096601. , PRLTAO 0031-9007 10.1103/PhysRevLett.107.096601Cornaglia, P.S., Usaj, G., Balseiro, C.A., (2009) Phys. Rev. Lett., 102, p. 046801. , PRLTAO 0031-9007 10.1103/PhysRevLett.102.046801Wimmer, M., Adagideli, I., Berber, S., Tomanek, D., Richter, K., Spin currents in rough graphene nanoribbons: Universal fluctuations and spin injection (2008) Physical Review Letters, 100 (17), p. 177207. , http://oai.aps.org/oai?verb=GetRecord&Identifier=oai:aps.org: PhysRevLett.100.177207&metadataPrefix=oai_apsmeta_2, DOI 10.1103/PhysRevLett.100.177207Katsnelson, M.I., Novoselov, K.S., Graphene: New bridge between condensed matter physics and quantum electrodynamics (2007) Solid State Communications, 143 (1-2), pp. 3-13. , DOI 10.1016/j.ssc.2007.02.043, PII S0038109807003043, Exploring graphene Recent research advancesFradkin, E., (1986) Phys. Rev. B, 33, p. 3263. , PRBMDO 1098-0121 10.1103/PhysRevB.33.3263Ludwig, A.W.W., Fisher, M.P.A., Shankar, R., Grinstein, G., (1994) Phys. Rev. B, 50, p. 7526. , PRBMDO 1098-0121 10.1103/PhysRevB.50.7526Shon, N.H., Ando, T., (1998) J. Phys. Soc. 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Superconductivity And Antiferromagnetism For An Extended Hubbard Hamiltonian: Role Of Correlated Hopping In A Single-band Model

An extended Hubbard model for a single band, including Coulomb repulsion and correlated hopping between nearest neighbors, is studied using a generalized mean-field approach. Antiferromagnetism and superconductivity are probed for arbitrary occupation number, near and away from half filling. Binding of pairs in the superconducting state of this purely repulsive model is mediated by the correlated hopping in the form of a covalent-bond configuration, with partial intrasite and intersite pairings. A region of coexistence is conjectured, the superconductivity being suppressed by the saturation of the staggered magnetic moment. Singlet superconducting nonmagnetic states are obtained for the almost-empty- or full-band cases. On the other hand, antiferromagnetism induces mixed s- and p-type superconductivities in the neighborhood of half filling. © 1993 The American Physical Society.4721144171442

Resonant Magnetic Tunnel Junction At 0° K: I-v Characteristics And Magnetoresistance

In this paper we analyze the main transport properties of a simple resonant magnetic tunnel junction (FM-IS-METAL-IS-FM structure) taking into account both elastic and magnon-assisted tunneling processes at low voltages and temperatures near 0° K. We show the possibility of magnetoresistance inversion as a consequence of inelastic processes and spin-dependent transmission coefficients. Resonant tunneling can also explain the effect of scattering by impurities located inside an insulating barrier. © 2005 American Institute of Physics.973Ando, Y., Murai, J., Kubota, H., Miyazaki, T., (2000) J. Appl. Phys., 87, p. 5209Xiang, X.H., Zhu, T., Du, J., Landry, G., Xiao, J.Q., (2002) Phys. Rev. B, 66, p. 174407Akerman, J.J., Roushchin, I.V., Slaughter, J.M., Dave, R.W., Schuller, I.K., (2003) Europhys. Lett, 63, p. 104Montaigne, F., Nassar, J., Vaurs, A., Van Dau Nguyen, F., Petroff, F., Schuhl, A., Pert, A., (1998) Appl. Phys. Lett., 73, p. 2829Miyazaki, T., Tezuka, N., (1995) J. Magn. Magn. Mater., 139, pp. L231Cabrera, G.G., Falicov, L.M., (1974) Phys. Status Solidi B, 61, p. 539(1975) Phys. Rev. B, 11, p. 2651Jullire, M., (1975) Phys. Lett., 54 A, p. 225Zhang, S., Levy, P.M., Marley, A.C., Parkin, S.S.P., (1997) Phys. Rev. Lett., 79, p. 3744Moodera, J.S., Nowak, J., Van De Veerdonk, R.J.M., (1998) Phys. Rev. Lett., 80, p. 2941Moodera, J.S., Mathon, G., (1999) J. Magn. Magn. Mater., 200, p. 248Cabrera, G.G., Garcia, N., (2002) Appl. Phys. Lett., 80, p. 1782Dartora, C.A., Cabrera, G.G., (2004) J. Appl. Phys., 95, p. 6058Zhang, X., Li, B.Z., Sun, G., Pu, F.C., (1997) Phys. Rev. B, 56, p. 5484N. Ryzhanova, G. Reiss, F. Kanjouri, and A. Vedyayev, arxiv.cond-mat/ 0401006 v2, 12 January 2004Zhang, S., Levy, P.M., (1999) Eur. Phys. J. B, 10, p. 599Tsymbal, E.Y., Sokolov, A., Sabirianov, I.F., Doudin, B., (2003) Phys. Rev. Lett., 90, p. 186602Tsymbal, E.Y., Pettifor, D.G., (2001) Phys. Rev. B, 64, p. 212401Jansen, R., Moodera, J.S., (1999) Appl. Phys. Lett., 75, p. 400Leclair, P., Kohlhepp, J.T., Swagten, H.J.M., De Jonge, W.J.M., (2001) Phys. Rev. Lett, 86, p. 1066De Teresa, J.M., (1999) Phys. Rev. Lett., 82, p. 4288Ferry, X., Goodnick, X., (1997) Transport in Nanostructures, , Cambridge University Press, CambridgeImry, Y., (1997) Introduction to Mesoscopic Physics, , Oxford University Press, New YorkKittel, C., (1963) Quantum Theory of Solids, , Wiley, New Yor