9 research outputs found
Transport properties of nanosystems with conventional and unconventional charge density waves
We report a systematic study of transport properties of nanosytems with
charge density waves. We demonstrate, how the presence of density waves
modifies the current-voltage characteristics. On the other hand hand, we show
that the density waves themselves are strongly affected by the applied voltage.
This self-consistent problem is solved within the formalism of the
nonequilibrium Green functions. The conventional charge density waves occur
only for specific, periodically distributed ranges of the voltage. Apart from
the low voltage regime, they are incommensurate and the corresponding wave
vectors decrease discontinuously when the voltage increases.Comment: 7 pages, 7 figures, revte
Spontaneous currents in a bosonic ring
Nonequilibrium dynamics of noninteracting bosons in a one-dimensional
ring-shaped lattice is studied by means of the Kinetic Monte Carlo method. The
system is approximated by the classical XY model (the kinetic term is
neglected) and then the simulations are performed for the planar classical
spins. We study the dynamics that follows a finite-time quench to zero
temperature. If the quench is slow enough the system can equilibrate and
finally reaches the ground state with uniform spin alignment. However, we show
that if the quench is faster than the relaxation rate, the system can get
locked in a current-carrying metastable state characterized by a nonzero
winding number. We analyze how the zero-temperature state depends on the quench
rate.Comment: 6 pages, 3 figure
Semiconductor quantum ring as a solid-state spin qubit
The implementation of a spin qubit in a quantum ring occupied by one or a few
electrons is proposed. Quantum bit involves the Zeeman sublevels of the highest
occupied orbital. Such a qubit can be initialized, addressed, manipulated, read
out and coherently coupled to other quantum rings. An extensive discussion of
relaxation and decoherence is presented. By analogy with quantum dots, the spin
relaxation times due to spin-orbit interaction for experimentally accessible
quantum ring architectures are calculated. The conditions are formulated under
which qubits build on quantum rings can have long relaxation times of the order
of seconds. Rapidly improving nanofabrication technology have made such ring
devices experimentally feasible and thus promising for quantum state
engineering.Comment: 16 pages, 3 figure 3 table