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We study dissipative tunneling in a double well potential that is driven close to a resonance between the lowest tunnel doublet and a singlet. While the coherent dynamics can be described well within a three-level approximation, dissipative…

Quantum Physics · Physics 2007-05-23 Sigmund Kohler , Peter Hänggi

Thermal control of exchange coupling between two strongly ferromagnetic layers through a weakly ferromagnetic Ni-Cu spacer and the associated magnetoresistance is investigated. The spacer, having a Curie point slightly above room…

Materials Science · Physics 2013-11-27 S. Andersson , V. Korenivski

We theoretically investigate impurity correlation and magnetic clustering effects on the long-range ferromagnetic ordering in diluted magnetic semiconductors, such as $\textrm{Ga}_{1-x}\textrm{Mn}_{x}\textrm{As}$, using analytical arguments…

Materials Science · Physics 2009-11-11 D. J. Priour , S. Das Sarma

We report results from Monte Carlo simulations of systems of magnetic dipoles that relax through quantum tunneling, much as Fe_8 crystals at very low temperature.For short times, a hole develops in suitably defined magnetic field…

Condensed Matter · Physics 2007-05-23 J. J. Alonso , J. F. Fernandez

A parametrized double-well potential is proposed to address the issue of the impact of shape deformability of some bistable physical systems, on their quantum dynamics and classical statistical mechanics. The parametrized double-well…

Statistical Mechanics · Physics 2021-10-07 F. Naha Nzoupe , Alain M. Dikande , C. Tchawoua

The phenomenon of quantum nucleation is studied in a nanometer-scale antiferromagnet with biaxial symmetry in the presence of a magnetic field at an arbitrary angle. Within the instanton approach, we calculate the dependence of the rate of…

Mesoscale and Nanoscale Physics · Physics 2015-06-24 Rong Lu , Yi Zhou , Jia-Lin Zhu , Bing-Lin Gu

A magnetotransport study in magnetically doped (Cd,Mn)Te 2D quantum wells reveals an apparent metal-insulator transition as well as an anomalous intermediate phase just on its metallic side. This phase is characterized by colossal…

Mesoscale and Nanoscale Physics · Physics 2010-01-10 J. Jaroszynski , T. Andrearczyk , G. Karczewski , J. Wróbel , T. Wojtowicz , Dragana Popovic , T. Dietl

We use a previously proposed theory for the temperature dependence of tunneling magnetoresistance to shed light on ongoing efforts to optimize spin valves. First we show that a mechanism in which spin valve performance at finite…

Mesoscale and Nanoscale Physics · Physics 2014-09-11 Karin Everschor-Sitte , Matthias Sitte , Allan H. MacDonald

The persistent current in two vertically coupled quantum rings containing few electrons is studied. We find that the Coulomb interaction between the rings in the absence of tunneling affects the persistent current in each ring and the…

Mesoscale and Nanoscale Physics · Physics 2008-11-30 L. K. Castelano , G. -Q. Hai , B. Partoens , F. M. Peeters

It is pointed out recently that the $\nu=1/m$ quantum Hall states in bilayer systems behave like easy plane quantum ferromagnets. We study the magnetotransport of these systems using their ``ferromagnetic" properties and a novel spin-charge…

Condensed Matter · Physics 2009-10-22 Tin-Lun Ho

A tunnel magnetic junction is considered with magnetic hard and magnetic soft layers of cubic symmetry. The magnetic switching is analyzed of the layers by a magnetic field perpendicular to the initial magnetizations. In such a situation,…

Materials Science · Physics 2009-08-11 S. G. Chigarev , E. M. Epshtein , P. E. Zilberman

An effect of paramagnetic impurity located in a vicinity of a quantum well (QW) on spin polarization of the carriers in the QW is analyzed theoretically. Within approach of Bardeen's tunneling Hamiltonian the problem is formulated in terms…

Mesoscale and Nanoscale Physics · Physics 2015-06-03 I. V. Rozhansky , N. S. Averkiev , E. Lahderanta

Based on the earlier published theory (\textit{Nature Mat}. \textbf{18}, 223--228 (2019)), a comprehensive experimental investigation of multiferroic quantum critical behavior of (Eu,Ba,Sr)TiO$_3$ polycrystalline and single crystal samples…

We present a theory of nonequilibrium quantum criticality in a coupled bilayer system of itinerant electron magnets. The model studied consists of the first layer subjected to an inplane current and open to an external substrate. The second…

Strongly Correlated Electrons · Physics 2010-04-13 So Takei , William Witczak-Krempa , Yong Baek Kim

Strongly nonlinear transport through Diluted Magnetic Semiconductor multiquantum wells occurs due to the interplay between confinement, Coulomb and exchange interaction. Nonlinear effects include the appearance of spin polarized stationary…

Mesoscale and Nanoscale Physics · Physics 2009-10-14 R. Escobedo , M. Carretero , L. L. Bonilla , G. Platero

Experimental studies of magnetoresistance in high-mobility wide quantum wells reveal oscillations which appear with an increase in temperature to 10 K and whose period is close to that of Shubnikov-de Haas oscillations. The observed…

Mesoscale and Nanoscale Physics · Physics 2010-11-01 S. Wiedmann , G. M. Gusev , O. E. Raichev , A. K. Bakarov , J. C. Portal

We present a theory of Coulomb blockade oscillations in tunneling through a pair of quantum dots connected by a tunable tunneling junction. The positions and amplitudes of peaks in the linear conductance are directly related, respectively,…

Condensed Matter · Physics 2009-10-28 K. A. Matveev , L. I. Glazman , H. U. Baranger

We study the problem of resonant tunneling between a Fermi liquid and the edge of a $\nu=1/3$ fractional quantum Hall state. In the limit of weak coupling, the system is adequately described within the sequential tunneling approximation. At…

Mesoscale and Nanoscale Physics · Physics 2007-05-23 C. L. Kane

The existence of a metal-insulator transition at zero magnetic field in two- dimensional electron systems has recently been confirmed in high mobility Si-MOSFETs. In this work, the temperature dependence of the resistivity of gated…

Mesoscale and Nanoscale Physics · Physics 2009-10-30 J. Lam , M. D'Iorio , D. Brown , H. Lafontaine

Near the Curie temperature of a ferromagnet the form of a domain wall changes from the Bloch type to (asymptotically) the linear Zhirnov wall. Unlike the simple 180 degree rotation of the magnetization vector in a Bloch wall, its absolute…

Other Condensed Matter · Physics 2007-05-23 Pavel Krotkov