Theory of Cross-correlated Electron–Magnon Transport Phenomena: Case of Magnetic Topological Insulator

Abstract

We study transport phenomena cross-correlated among the heat and electric currents of magnons and Dirac electrons on the surface of ferromagnetic topological insulators. For a perpendicular magnetization, we calculate magnon-(electron-) drag anomalous Nernst/Seebeck (anomalous Ettingshausen/Peltier) effects and magnon-/electron-drag thermal Hall effects. The magnon-drag thermoelectric effects are interpreted to be caused by magnon-induced electromotive force. When the magnetization has in-plane components, there arise thermal/thermoelectric analogs of anisotropic magnetoresistance (AMR). In the insulating state, the thermal AMR is realized as a magnonic analog of AMR.

Microscopic theory of magnon-drag electron flow in ferromagnetic metals

“…In this paper, we are interested in the magnon-drag process, which corresponds to taking the magnon heatcurrent density j Q mag,i for j Q i in Eq. (22). As for A in Eq.…”

Theory of Huge Thermoelectric Effect Based on Magnon Drag Mechanism: Application to Thin-Film Heusler Alloy

“…The contribution of the magnon drag to the Seebeck effect has been studied experimentally [15][16][17][18] and theoretically [19][20][21][22][23] from the 1960s. However, it appears that the magnon drag, related with an impurity band such as for the present alloy, is not sufficiently understood.…”

“…Model Hamiltonian and Formulation of Electric and Thermal transports.-To study the magnon drag based on the electronic state shown in Fig. 1(c), we use a following model Hamiltonian [14,[21][22][23].…”

“…V T τ [j e (τ )j mag Q (0)] , where τ is an imaginary time and T τ denotes the imaginary time ordering operator [22,23]. By the second order perturbation on the exchange interaction based on the Green's function of electrons, Eq.…”

Voltage-control of damping constant in magnetic-insulator/topological-insulator bilayers

“…So far, the magnon spin transport in the FI/TI bilayer lacks microscopic theory with few exceptions. 68,69 However, from the bulk of magnon spin transport, 66 the control of τ m results in the modification of all transport properties, including the magnon spin conductivity. In the presence of a TI contact, interfacial magnons are scattered by conducting Dirac electrons on the TI surface.…”