Using academic notebooks to support achievement and promote positive environments in differentiated classrooms

Authors Examine How the Use of Academic Notebooks Impacts Collaborative Learning Experiences of Young Adolescent

The role of symmetry on interface states in magnetic tunnel junctions

When an electron tunnels from a metal into the barrier in a magnetic tunnel junction it has to cross the interface. Deep in the metal the eigenstates for the electron can be labelled by the point symmetry group of the bulk but around the interface this symmetry is reduced and one has to use linear combinations of the bulk states to form the eigenstates labelled by the irreducible representations of the point symmetry group of the interface. In this way there can be states localized at the interface which control tunneling. The conclusions as to which are the dominant tunneling states are different from that conventionally found.Comment: 14 pages, 5 figures, accepted in PRB, v2: reference 3 complete

Spin-dependent tunneling in magnetic tunnel junctions

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of spindependent tunneling. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in magnetic tunnel junctions. Starting from early experiments on spin-dependent tunneling and their interpretation, we consider thereafter recent experiments and models, which highlight the role of the electronic structure of the ferromagnets, the insulating layer and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR

Spin-dependent tunneling in magnetic tunnel junctions

The phenomenon of electron tunneling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunneling in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunneling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of spindependent tunneling. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in magnetic tunnel junctions. Starting from early experiments on spin-dependent tunneling and their interpretation, we consider thereafter recent experiments and models, which highlight the role of the electronic structure of the ferromagnets, the insulating layer and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR

Electroneutrality and the Friedel sum rule in a Luttinger liquid

Screening in one-dimensional metals is studied for arbitrary electron-electron interactions. It is shown that for finite-range interactions (Luttinger liquid) electroneutrality is violated. This apparent inconsistency can be traced to the presence of external screening gates responsible for the effectively short-ranged Coulomb interactions. We also draw attention to the breakdown of linear screening for wavevectors close to 2 K_f.Comment: 4 pages REVTeX, incl one figure, to appear in Phys.Rev.Let

Quantization of Solitons and the Restricted Sine-Gordon Model

We show how to compute form factors, matrix elements of local fields, in the restricted sine-Gordon model, at the reflectionless points, by quantizing solitons. We introduce (quantum) separated variables in which the Hamiltonians are expressed in terms of (quantum) tau-functions. We explicitly describe the soliton wave functions, and we explain how the restriction is related to an unusual hermitian structure. We also present a semi-classical analysis which enlightens the fact that the restricted sine-Gordon model corresponds to an analytical continuation of the sine-Gordon model, intermediate between sine-Gordon and KdV.Comment: 29 pages, Latex, minor updatin

A Comment on Masses, Quantum Affine Symmetries and PP-Wave Backgrounds

Two dimensional light cone world sheet massive models can be used to define good string backgrounds.In many cases these light cone world sheet lagrangians flow from a CFT in the UV to a theory of massive particles in the IR. The relevant symmetry in the IR, playing a similar role to Virasoro in the UV, are quantum affine Kac Moody algebras. Finite dimensional irreps of this algebra are associated with the spectrum of massive particles. The case of N=0 Sine Gordon at the N=2 point is associated with a Landau Ginzburg model that defines a good string background. For the world sheet symmetry $(N=2) \otimes U_{q}(\hat{Sl(2)})$ the N=2 piece is associated with the string conformal invariance and the $U_{q}(\hat{Sl(2)})$ piece with the world sheet RG. The two dimensional light cone world sheet massive model can be promoted to a CFT by adding extra light cone fields $X^{-}$ and $X^{+}$. From the point of view of the quantum affine symmetry these two fields are associated, respectively, with the center and the derivation of the affine Kac Moody algebra.Comment: 9 pages. Typos correcte

Telling the Story of Stepfamily Beginnings: The Relationship between Young-adult Stepchildren’s Stepfamily Origin Stories and their Satisfaction with the Stepfamily

The current study adopts a narrative perspective in examining the content of 80 stepchildren’s stepfamily origin stories. Results reveal five types of stepfamily origin stories: Sudden, Dark-sided, Ambivalent, Idealized, and Incremental. Results support the hypothesis that story type would predict differences in family satisfaction; stepchildren who described their stepfamily origins as Idealized were more satisfied than those whose origins were Dark-sided or Sudden. Overall, participants framed their stepfamily identity more positively when their stepfamily beginnings were characterized by closeness, friendship, and even expected ups and downs, rather than when they were left out of the process of negotiating or forming the stepfamily and when the beginnings were tainted by issues they considered to be dark. Stepparents or practitioners may benefit from these findings by examining the means by which stepparents may involve stepchildren in the process of stepfamily courtship, facilitate closeness, and set up realistic expectations for negotiating stepfamily life

Effect of interface bonding on spin-dependent tunneling from the oxidized Co surface

We demonstrate that the factorization of the tunneling transmission into the product of two surface transmission functions and a vacuum decay factor allows one to generalize Julliere's formula and explain the meaning of the ``tunneling density of states'' in some limiting cases. Using this factorization we calculate spin-dependent tunneling from clean and oxidized fcc Co surfaces through vacuum into Al using the principal-layer Green's function approach. We demonstrate that a monolayer of oxygen on the Co (111) surface creates a spin-filter effect due to the Co-O bonding which produces an additional tunneling barrier in the minority-spin channel. This changes the minority-spin dominated conductance for the clean Co surface into a majority spin dominated conductance for the oxidized Co surface.Comment: 7 pages, revtex4, 4 embedded eps figure

A Classification of random Dirac fermions

We present a detailed classification of random Dirac hamiltonians in two spatial dimensions based on the implementation of discrete symmetries. Our classification is slightly finer than that of random matrices, and contains thirteen classes. We also extend this classification to non-hermitian hamiltonians with and without Dirac structure.Comment: 15 pages, version2: typos in the table of classes are correcte