Far from equilibrium quantum systems
Low-dimensional
systems are interesting for theoretical investigations, as
they admit
ordering tendencies, leading to collective quantum states
that are
difficult to realize in three-dimensional systems.
Understanding the
transport properties of such low-dimensional strongly
correlated
systems is a challenging open problem. So far, most of the
theoretical
studies concentrated on the close-to-equilibrium situation
by using the
linear response, while very little is known about the
physics of such
systems far from equilibrium. On the other hand, new
quantum phases and
interesting physical phenomena may appear in the far from
equilibrium
regime.
Quantum
traffic jam
Negative differential conductivity in the XXZ spin chain
We
have shown [1,2] that, when a finite anisotropic
Heisenberg spin-1/2
chain in the gapped regime is driven far from
equilibrium, oppositely
polarized ferromagnetic domains build up at the
edges of the chain,
thus suppressing quantum spin transport (quantum
traffic jam). As a
consequence, a negative
differential
conductivity
regime arises, where increasing the driving
decreases the current. This
phenomenon arises as an outcome of the interplay
between coherent
quantum dynamics of the spin chain and incoherent
spin pumping. We have also discussed the negative
differential conductivity phenomenon
in the context of charge transport in strongly
correlated electron
systems, e.g., for the Hubbard model. Negative
differential conductivity is also the basis of
rectifiers, and we have investigated the
ingredients for a spin diode in a segmented spin
chain, with the counterintuitive property of
becoming perfect at the thermodynamic limit [3].
Negative differential conductivity in the XXZ spin chain
References
[1]
G.
Benenti, G. Casati, T. Prosen and D. Rossini, Negative differential
conductivity in
far-from-equilibrium quantum spin chains,
Europhys. Lett. 85,
37001 (2009).
[2] G. Benenti, G. Casati, T. Prosen, D. Rossini and M. Znidaric, Charge and spin transport in strongly correlated one-dimensional quantum systems driven far from equilibrium, Phys. Rev. B 80, 035110 (2009).
[3] V. Balachandran, G. Benenti, E. Pereira. G. Casati and D. Poletti, Perfect diode in quantum spin chains, preprint arXiv:1707.08823 [cond-mat.stat-mech].
[2] G. Benenti, G. Casati, T. Prosen, D. Rossini and M. Znidaric, Charge and spin transport in strongly correlated one-dimensional quantum systems driven far from equilibrium, Phys. Rev. B 80, 035110 (2009).
[3] V. Balachandran, G. Benenti, E. Pereira. G. Casati and D. Poletti, Perfect diode in quantum spin chains, preprint arXiv:1707.08823 [cond-mat.stat-mech].