Quantum spin torque driven transmutation of antiferromagnetic Mott insulator

Abstract

The standard model of spin-transfer torque (STT) in antiferromagnetic spintronics considers exchange of angular momentum between quantum spins of flowing electrons and noncollinear-to-them localized spins treated as classical vectors. These vectors are assumed to realize Néel order in equilibrium, $\uparrow \downarrow \dots \uparrow \downarrow$, and their STT-driven dynamics is described by the Landau-Lifshitz-Gilbert (LLG) equation. However, many experimentally employed materials (such as archetypal NiO) are strongly electron-correlated antiferromagnetic Mott insulators (AFMI) where localized spins form a ground state quite different from the unentangled Néel state $|\uparrow \downarrow \dots \uparrow \downarrow ⟩$. The true ground state is entangled by quantum spin fluctuations, leading to expectation value of all localized spins being zero, so that LLG dynamics of classical vectors of fixed length rotating due to STT cannot even be initiated. Instead, a fully quantum treatment of both conduction electrons and localized spins is necessary to capture exchange of spin angular momentum between them, denoted as quantum STT. We use a recently developed time-dependent density matrix renormalization group approach to quantum STT to predict how injection of a spin-polarized current pulse into a normal metal layer coupled to AFMI overlayer via exchange interaction and possibly small interlayer hopping -- which mimics, e.g., topological-insulator/NiO bilayer employed experimentally -- will induce nonzero expectation value of AFMI localized spins. This new nonequilibrium phase is a spatially inhomogeneous ferromagnet with zigzag profile of localized spins. The total spin absorbed by AFMI increases with electron-electron repulsion in AFMI, as well as when the two layers do not exchange any charge.

7 pages, 5 figures; Supplemental Material, including a movie, is available from this URL https://wiki.physics.udel.edu/qttg/Publications

References in corpus (18)

• Spin Transfer Torques
• Real time evolution using the density matrix renormalization group
• Spin pumping and spin-transfer torques in antiferromagnets
• Subterahertz spin pumping from an insulating antiferromagnet
• Phenomenology of Current-Induced Dynamics in Antiferromagnets
• Double Counting in LDA+DMFT - The Example of NiO
• Quantum dynamics and entanglement of spins on a square lattice
• Entanglement and factorized ground states in two-dimensional quantum antiferromagnets
• Spin-transfer torques in anti-ferromagnetic metals from first principles
• Ultrafast Switching of Antiferromagnets via Spin-transfer Torque
• Non-equilibrium electronic transport in a one-dimensional Mott insulator
• Spin Transfer Torque in Antiferromagnetic Spin-Valves: From Clean to Disordered Regimes
• First-principles spin-transfer torque in CuMnAs$|$GaP$|$CuMnAs junctions
• Magnon versus electron mediated spin-transfer torque exerted by spin currents across antiferromagnetic insulator to switch magnetization of adjacent ferromagnetic metal
• Non-classical spin transfer effects in an antiferromagnet
• Energy and momentum conservation in spin transfer
• Derivation of a time dependent Schrödinger equation as quantum mechanical Landau-Lifshitz-Bloch equation
• Löwdin's symmetry dilemma within Green functions theory for the one-dimensional Hubbard model

Cited by in corpus (10)

• Spintronics meets density matrix renormalization group: Quantum spin torque driven nonclassical magnetization reversal and dynamical buildup of long-range entanglement
• Quantum many-body states and Green functions of nonequilibrium electron-magnon systems: Localized spin operators vs. their mapping to Holstein-Primakoff bosons
• Topological nature of the proper spin current and the spin-Hall torque
• When can localized spins interacting with conduction electrons in ferro- or antiferromagnets be described classically via the Landau-Lifshitz equation: Transition from quantum many-body entangled to quantum-classical nonequilibrium states
• Fate of entanglement in magnetism under Lindbladian or non-Markovian dynamics and conditions for their transition to Landau-Lifshitz-Gilbert classical dynamics
• Transient dynamics of a magnetic impurity coupled to superconducting electrodes: exact numerics versus perturbation theory
• Electron-mediated entanglement of two distant macroscopic ferromagnets within a nonequilibrium spintronic device
• Effects of the dynamical magnetization state on spin transfer
• Nonclassical dynamics of Néel vector and magnetization accompanied by THz and high-harmonic radiation from ultrafast-light-driven NiO antiferromagnet insulator
• Geometrical torque on magnetic moments coupled to a correlated antiferromagnet