130 research outputs found
Spin-catalyzed hopping conductivity in disordered strongly interacting quantum wires
In one-dimensional electronic systems with strong repulsive interactions,
charge excitations propagate much faster than spin excitations. Such systems
therefore have an intermediate temperature range [termed the "spin-incoherent
Luttinger liquid'" (SILL) regime] where charge excitations are "cold" (i.e.,
have low entropy) whereas spin excitations are "hot." We explore the effects of
charge-sector disorder in the SILL regime in the absence of external sources of
equilibration. We argue that the disorder localizes all charge-sector
excitations; however, spin excitations are protected against full localization,
and act as a heat bath facilitating charge and energy transport on
asymptotically long timescales. The charge, spin, and energy conductivities are
widely separated from one another. The dominant carriers of energy are neither
charge nor spin excitations, but neutral "phonon" modes, which undergo an
unconventional form of hopping transport that we discuss. We comment on the
applicability of these ideas to experiments and numerical simulations.Comment: 14 pages, 6 figure
Instability of many-body localized systems as a phase transition in a nonstandard thermodynamic limit
The many-body localization (MBL) phase transition is not a conventional
thermodynamic phase transition. Thus to define the phase transition one should
allow the possibility of taking the limit of an infinite system in a way that
is not the conventional thermodynamic limit. We explore this for the so-called
"avalanche" instability due to rare thermalizing regions in the MBL phase for
quenched-random systems in more than one spatial dimension, finding an
unconventional way of scaling the systems so that they do have a type of phase
transition. These arguments suggest that the MBL phase transition in systems
with short-range interactions in more than one dimension is a transition where
entanglement in the eigenstates begins to spread in to some typical regions:
the transition is set by when the avalanches start. Once this entanglement gets
started, the system does thermalize. From this point of view, the much-studied
case of one-dimensional MBL with short-range interactions is a special case
with a different, and in some ways more conventional, type of phase transition.Comment: 10 pages, 2 figure
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