Nonadiabaticity in spin pumping under relaxation

Abstract

Using a minimum model consisting of a magnetic quantum dot and an electron lead, we investigate spin pumping by its precessing magnetization. Focusing on the "adiabaticity", which is quantified using a comparison between the frequency of precession and the relaxation rate of the relevant system, we investigate the role of nonadiabaticity in spin pumping by obtaining the dependence of the spin current generated on the frequency of precession using full counting statistics. This evaluation shows that the steady-state population of the quantum dot remains unchanged by the precession owing to the rotational symmetry about the axis of precession. This implies that in the adiabatic limit the spin current is absent and that spin pumping is entirely a nonadiabatic effect. We also find that the nonadiabatic spin current depends linearly on the frequency in the low-frequency regime and exhibits an oscillation in the high-frequency regime. The oscillation points to an enhancement of spin pumping by tuning the frequency of precession

Photoinduced collective mode, inhomogeneity, and melting in a charge-order system

“…We note that the generated kinks themselves show little motions 32 . This picture is different from the case of the purely one-dimensional model where a CO decrease is ascribed to solitonic motions of kinks 25 . In any case, the phenomena occur in the highly nonlinear regime, as seen, for example, from the threshold behavior of the induced in-gap density of states.…”

“…Note that by using HF approximation, we are implying higher dimension (quasi-one-dimensional) systems in mind, rather than trying to investigate a purely onedimensional system, as studied in Ref. 25 .…”

“…When ω p ∆ CO , during the pump light is shined δ decreases and stays constant afterwards. This is interpreted as the one-particle excitation where the energy of light is absorbed by the fermion system through photocarrier generation 25,27 .…”

Exciton transport enhancement across quantum Su-Schrieffer-Heeger lattices with quartic nonlinearity

“…We expect that our results motivate the study of the impact on different weak non-linearities in strongly-correlated systems, such as a cubic anharmonicity, and of alternative particle-phonon coupling schemes (e.g. a local coupling as in Holstein models [19][20][21][22][23][24][25][26][27] ), to determine how they can affect their already very rich physics.…”

“…On the other hand, more advanced schemes take full account of the environmental dynamics [2][3][4] , but are numerically more demanding and applicable to harmonic environments only. Hence, most studies have adopted the first approach, which results in Markovian decoherence [5][6][7][8][9][10][11][12][13][14][15][16][17][18] , or consider dynamical properties for lattice harmonicity [19][20][21][22][23][24][25][26][27] . Taking into account specific inter-atomic potential energy terms beyond this harmonic approximation remains a challenge.…”