Ultrafast Spin Dynamics in Photodoped Spin-Orbit Mott Insulator Sr2IrO4

Abstract

Ultrafast photodoping of the Mott insulators, possessing strong correlation between electronic and magnetic degrees of freedom, holds promise for launching an ultrafast dynamics of spins which cannot be described in terms of conventional models of ultrafast magnetism. Here we study the ultrafast laser-induced dynamics of the magnetic order in a novel spin-orbit Mott insulator Sr 2 IrO 4 featuring an uncompensated pattern of antiferromagnetic spin ordering. Using the transient magneto-optical Kerr effect sensitive to the net magnetization, we reveal that photodoping by femtosecond laser pulses with photon energy above the Mott gap launches melting of the antiferromagnetic order seen as ultrafast demagnetization with a characteristic time of 300 fs followed by a sub-10-ps recovery. Nonequilibrium dynamical mean-field theory calculations based on the single-band Hubbard model confirm that ultrafast demagnetization is primarily governed by the laser-induced generation of electron-hole pairs, although the precise simulated time dependencies are rather different from the experimentally observed ones. To describe the experimental results, here we suggest a phenomenological model which is based on Onsager's formalism and accounts for the photogenerated electron-hole pairs using the concepts of holons and doublons.

Excitonic magnetism at the intersection of spin-orbit coupling and crystal-field splitting

“…1(a). (11) found in states with total onsite angular momentum J = 0, 1, 2, and (c) shows analogous weights in eigenstates of (21), i.e., in the levels S 0 , D 1/2 , and S 3 of Fig. 1(a).…”

“…With the transition to checkerboard order, total onsite angular momentum J becomes more relevant, as can be inferred from the weight (11) in eigenstates |J = 0, 1, 2 . The J = 0 state quickly gains weight with the onset of checkerboard AFM order, as shown in Fig.…”

“…With five t 2g electrons, its J = 3 2 levels are completely filled and the J = 1 2 level is half filled. The resulting effective singleband description focusing on the J = 1 2 states is even robust enough to survive in doped regimes, where Fermi arcs [9] and hints of superconductivity [10] have been reported, as well as photodoping [11]. While a description in terms of J = 1 2 is thus well established for a single hole in the t 2g levels of Ru or Ir and forms the basis for the proposed spin-liquid scenario, the situation for two holes is less clear.…”

Resonant Pumping of d−d Crystal Field Electronic Transitions as a Mechanism of Ultrafast Optical Control of the Exchange Interactions in Iron Oxides

“…The symmetric part of the exchange energy Wex between two magnetic sublattices S1 and S2 Wex = JS1S2 is responsible for the very existence of long-range magnetic order. During recent years, the modulation of the symmetric exchange interaction by femtosecond laser pulses has been a subject of experimental and theoretical studies [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. Its antisymmetric counterpart, the relativistic Dzyaloshinskii-Moriya energy WD = D×[S1×S2], contributes to the emergence of weak ferromagnetism [20], multiferroicity [21] and magnetic skyrmions [22].…”

Far- and midinfrared excitation of large amplitude spin precession in the ferromagnetic semiconductor InMnAs

“…The model ignores the electronic structure of magnets and suggests that the result of laser excitation is insensitive to the photon energy and only depends on the duration of the laser pulse and the total energy transfered from light to magnet. However, recent demonstrations of magnetic spin response by optical pumping of d-d electronic transitions in iron garnet [6,7], charge transfer in Sr 2 IrO 4 [8] as well as f-f transitions in DyFeO 3 [9] and TmFeO 3 [10] have naturally raised questions about electronic excitations mediating the control of magnetism by light.…”