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A simple and computationally efficient algorithm enables implementing negative temperature values in a spin dynamics simulation. The algorithm uses a Langevin spin dynamics thermostat with a negative damping parameter, enabling the…

Materials Science · Physics 2024-03-05 Pui-Wai Ma , Sergei L. Dudarev

We demonstrate a strong dependence of the effective damping on the nanomagnet size and the particular spin-wave mode that can be explained by the theory of intralayer transverse-spin-pumping. The effective Landau-Lifshitz damping is…

Mesoscale and Nanoscale Physics · Physics 2013-03-15 Hans T. Nembach , Justin M. Shaw , Carl T. Boone , T. J. Silva

We suggest a simple model to describe the reversible field-induced transfer of a single Xe-atom in a scanning tunneling microscope, --- the Eigler-switch. The inelasticly tunneling electrons give rise to fluctuating forces on and damping of…

Condensed Matter · Physics 2016-08-14 Mads Brandbyge , Per Hedegård

We study the dynamical thermal conductivity of the Kitaev spin model on a two-leg ladder. In contrast to conventional integrable one-dimensional spin systems, we show that heat transport is completely dissipative. This is a direct…

Strongly Correlated Electrons · Physics 2017-07-19 Alexandros Metavitsiadis , Wolfram Brenig

We theoretically investigate the electric transport in the pseudogap state of High-Tc cuprates. Starting from the repulsive Hubbard model, we perform the microscopic calculation to describe the pseudogap phenomena which are induced by the…

Strongly Correlated Electrons · Physics 2016-08-31 Youichi Yanase

Employing the self-consistent Green's function approach, we studied the temperature dependence of the spin-wave stiffness in diluted magnetic semiconductors. Note that the Green's function approach includes the spatial and temperature…

Materials Science · Physics 2009-11-11 Shih-Jye Sun , Hsiu-Hau Lin

We study anomalous diffusion for one-dimensional systems described by a generalized Langevin equation. We show that superdiffusion can be classified in normal superdiffusion and fast superdiffusion. For fast superdiffusion, we prove that…

Statistical Mechanics · Physics 2009-11-10 Ismael V. L. Costa , Rafael Morgado , Marcos V. B. T. Lima , Fernando A. Oliveira

Spin-transfer torques induced by temperature gradients in conducting ferromagnets are calculated microscopically for smooth magnetization textures. Temperature gradients are treated a la Luttinger by introducing a fictitious gravitational…

Mesoscale and Nanoscale Physics · Physics 2016-10-12 H. Kohno , Y. Hiraoka , M. Hatami , G. E. W. Bauer

Thermodynamic flunctuations in BaFe2As2 is addressed with a first-principles formulation of the Helmholtz energy by accounting for the mixture of various electronic states each distinguished by different spin orientation distributions. We…

Superconductivity · Physics 2014-02-25 Y. Wang , S. L. Shang , L. Q. Chen , Z. K. Liu

The localized magnon modes of isolated $k\pi$ skyrmions on a field-polarized background are analyzed based on the Landau-Lifshitz-Gilbert equation within the terms of an atomistic classical spin model, with system parameters based on the…

Mesoscale and Nanoscale Physics · Physics 2019-01-02 Levente Rózsa , Julian Hagemeister , Elena Y. Vedmedenko , Roland Wiesendanger

Quantum criticality has attracted considerable attention both theoretically and experimentally as a way to describe part of the phase diagram of strongly correlated systems. A scale-invariant fluctuation spectrum at a quantum critical point…

Strongly Correlated Electrons · Physics 2015-10-28 Stefan Kirchner , Qimiao Si

A unified model of molecular and atomistic spin dynamics is presented enabling simulations both in microcanonical and canonical ensembles without the necessity of additional phenomenological spin damping. Transfer of energy and angular…

We investigate spin transport by thermally excited spin waves in an antiferromagnetic insulator. Starting from a stochastic Landau-Lifshitz-Gilbert phenomenology, we obtain the out-of-equilibrium spin-wave properties. In linear response to…

Mesoscale and Nanoscale Physics · Physics 2018-11-05 Scott A. Bender , Hans Skarsvåg , Arne Brataas , Rembert A. Duine

We apply linear response theory to a general, inhomogeneous, stationary stellar system, with particular emphasis on dissipative processes analogous to Landau damping. Assuming only that the response is causal, we show that the irreversible…

Astrophysics · Physics 2007-05-23 Robert W. Nelson , Scott Tremaine

We examine spin diffusion in a two-component homogeneous Fermi gas in the normal phase. Using a variational approach, analytical results are presented for the spin diffusion coefficient and the related spin relaxation time as a function of…

Quantum Gases · Physics 2011-03-18 G. M. Bruun

Precessing magnetization in a thin film magnetic insulator pumps spins into adjacent metals; however, this phenomenon is not quantitatively understood. We present a theory for the dependence of spin-pumping on the transverse mode number and…

Mesoscale and Nanoscale Physics · Physics 2013-08-29 André Kapelrud , Arne Brataas

Time-resolved scanning Kerr effect microscopy has been used to study magnetization dynamics in Permalloy thin films excited by transient magnetic pulses generated by a micrometer-scale transmission line structure. The results are consistent…

Other Condensed Matter · Physics 2007-05-23 Zhigang Liu , Fabian Giesen , Xiaobin Zhu , Richard D. Sydora , Mark R. Freeman

In this article we report on micromagnetic simulations performed on a permalloy nanostructure in presence of a uniform thermal gradient. Our numerical simulations show that heat flow is an effective mean to compensate the damping, and that…

Mesoscale and Nanoscale Physics · Physics 2012-07-31 S. Borlenghi , M. Franchin , H. Fangohr , L. Bergqvist , a. Delin

In a stochastic heat engine driven by a cyclic non-equilibrium protocol, fluctuations in work and heat give rise to a fluctuating efficiency. Using computer simulations and tools from large deviation theory, we have examined these…

Statistical Mechanics · Physics 2014-10-27 Todd R. Gingrich , Grant M. Rotskoff , Suriyanarayanan Vaikuntanathan , Phillip L. Geissler

Spin transport equations in a non-homogeneous ferromagnet are derived in the limit where the sd exchange coupling between the electrons in the conduction band and those in the d band is dominant. It is shown that spin diffusion in…

Mesoscale and Nanoscale Physics · Physics 2009-11-13 M. Benakli , J. Hohlfeld , A. Rebei