Current-induced switching in transport through anisotropic magnetic molecules

Abstract

Anisotropic single-molecule magnets may be thought of as molecular switches, with possible applications to molecular spintronics. In this paper, we consider current-induced switching in singlemolecule junctions containing an anisotropic magnetic molecule. We assume that the carriers interact with the magnetic molecule through the exchange interaction and focus on the regime of high currents in which the molecular spin dynamics is slow compared to the time which the electrons spend on the molecule. In this limit, the molecular spin obeys a non-equilibrium Langevin equation which takes the form of a generalized Landau-Lifshitz-Gilbert equation and which we derive microscopically by means of a non-equilibrium Born-Oppenheimer approximation. We exploit this Langevin equation to identify the relevant switching mechanisms and to derive the current-induced switching rates. As a byproduct, we also derive S-matrix expressions for the various torques entering into the Landau-Lifshitz-Gilbert equation which generalize previous expressions in the literature to non-equilibrium situations.

Limit cycles and chaos in the current through a quantum dot

“…[26] and [28]. This possibility is also closely related to transport through single molecular magnets [29][30][31][32] , for which our large spin would map to a magnetic atom and the isolated levels of our quantum dot to molecular orbitals.…”

Antidamping spin-orbit torque driven by spin-flip reflection mechanism on the surface of a topological insulator: A time-dependent nonequilibrium Green function approach

“…However, even for slow evolution of m(t), corrections [31] to the adiabatic GF are needed to describe dissipation effects such as Gilbert damping or the charge current which can be pumped [34] …”

“…The so-called adiabatic expansion, which yields corrections beyond the strictly adiabatic limit, is traditionally performed using the Wigner representation [33] in which the fast and slow time scales are easily identifiable [31]. The slow motion implies that the NEGFs vary slowly with the central time t c = (t + t )/2 while they change fast with the relative time t r = t − t .…”

“…In Sec. II, we present the adiabatic expansion of time-dependent NEGFs, in a representation that is alternative to Wigner representation [33] (usually employed for this type of derivation [31]), and derive expressions for torque, charge pumping, and Gilbert damping. In Sec.…”

“…In order to analyze spatial dependence of SOT in the device geometry of Fig. 1, while not assuming anything a priori about the orientation of fieldlike and antidamping-like components of SOT, we employ adiabatic expansion [31] of time-dependent nonequilibrium Green functions (NEGFs) [32,33] to derive formulas for torque, charge pumping [34,35], and Gilbert damping [36] in the presence of SOC. The NEGFbased formula for SOT naturally splits into four components, determined by their behavior (even or odd) under the time and bias voltage reversal.…”