INVESTIGADORES
REYNOSO Andres Alejandro
artículos
Título:
Dephasing and hyperfine interaction in carbon nanotube double quantum dots: The clean limit
Autor/es:
ANDRES A. REYNOSO; KARSTEN FLENSBERG
Revista:
PHYSICAL REVIEW B
Editorial:
AMER PHYSICAL SOC
Referencias:
Lugar: New York; Año: 2011 vol. 84 p. 205449 - 205468
ISSN:
1098-0121
Resumen:
We consider
theoretically 13C-hyperfine interaction-induced dephasing in carbon
nanotubes double quantum dots with curvature-induced spin-orbit coupling. For
two electrons initially occupying a single dot, we calculate the average return
probability after separation into the two dots, which have random nuclear spin
configurations. We focus on the long-time saturation value of the return
probability, P\infty.
Because of the valley degree of freedom, the analysis is more complex than in,
for example, GaAs quantum dots, which have two distinct P\infty values depending on the magnetic field. Here,
the prepared and the measured states are nonunique because two electrons in the
same dot are allowed in six different states. Moreover, for one electron in
each dot, sixteen states exist and therefore are available for being mixed by
the hyperfine field. The return probability experiment is found to be strongly
dependent on the prepared state, the external magnetic field both Zeeman and
orbital effects and the spin-orbit splitting. The lowest saturation value,
being P\infty =1/3, occurs
at zero magnetic field for nanotubes with spin-orbit coupling and the initial
state being the ground state, this situation is equivalent to double dots
without the valley degree of freedom. In total, we report nine dynamically
different situations that give P\infty
=1/3, 3/8, 2/5, 1/2, and for valley antisymmetric prepared states in an axial
magnetic field, P\infty=1.
When the ground state is prepared, the ratio between the spin-orbit splitting
and the Zeeman energy due to a perpendicular magnetic field can tune the
effective hyperfine field continuously from being three dimensional to two
dimensional giving saturation values from P\infty
=1/3 to 3/8.