8 research outputs found
Analytical description of spin-Rabi oscillation controlled electronic transitions rates between weakly coupled pairs of paramagnetic states with S=1/2
We report on an analytical description of spin-dependent electronic
transition rates which are controlled by a radiation induced spin-Rabi
oscillation of weakly spin-exchange and spin-dipolar coupled paramagnetic
states (S=1/2). The oscillation components (the Fourier content) of the net
transition rates within spin-pair ensembles are derived for randomly
distributed spin resonances with account of a possible correlation between the
two distributions that correspond to the two individual pair partners. The
results presented here show that when electrically or optically detected Rabi
spectroscopy is conducted under an increasing driving field B_ 1, the Rabi
spectrum evolves from a single resonance peak at s=\Omega_R, where
\Omega_R=\gamma B_1 is the Rabi frequency (\gamma is the gyromagnetic ratio),
to three peaks at s= \Omega_R, s=2\Omega_R, and at low s<< \Omega_R. The
crossover between the two regimes takes place when \Omega_R exceeds the
expectation value \delta_0 of the difference of the Zeeman energies within the
pairs, which corresponds to the broadening of the magnetic resonance lines in
the presence of disorder caused by hyperfine field or distributions of Lande
g-factors. We capture this crossover by analytically calculating the shapes of
all three peaks at arbitrary relation between \Omega_R and \delta_0. When the
peaks are well-developed their widths are \Delta s ~ \delta_0^2/\Omega_R.Comment: 10 page, 5 figure
Interplay of spin-orbit coupling and Zeeman splitting in the absorption lineshape of 2D fermions
We suggest that electron spin resonance (ESR) experiment can be used as a
probe of spinon excitations of hypothetical spin-liquid state of frustrated
antiferromagnet in the presence of asymmetric Dzyaloshinskii-Moriya (DM)
interaction. We describe assumptions under which the ESR response is reduced to
the response of 2D electron gas with Rashba spin-orbit coupling. Unlike
previous treatments, the spin-orbit coupling, \Delta_{SO}, is not assumed small
compared to the Zeeman splitting, \Delta_Z. We demonstrate that ESR response
diverges at the edges of the absorption spectrum for ac magnetic field
perpendicular to the static field. At the compensation point,
\Delta_{SO}\approx \Delta_Z, the broad absorption spectrum exhibits features
that evolve with temperature, T, even when T is comparable to the Fermi energy.Comment: 11 pages, 6 figure
Dissipative dynamics of qubits driven by a bichromatic field in the dispersive regime
We study the coherent dynamics of relaxing qubits driven by a bichromatic
radiation in the dispersive regime, when detuning of the frequency
of a longitudinal radiofrequency field from the Rabi frequency
in a transverse microwave field is comparable in magnitude to
and . We analytically describe this regime beyond the
rotating wave approximation and find that the dominant feature of dynamics of
qubits is the shift of the Rabi frequency caused by the dynamical Zeeman and
Bloch-Siegert-like effects. These fundamental effects can be experimentally
separated because, unlike the Bloch-Siegert effect, the dynamical Zeeman effect
depends on the detuning sign. Our theoretical results are in a good agreement
with the experimental data obtained in pulse EPR for the centers in
crystalline quartz.Comment: 11 pages, 4 figure