4,335 research outputs found
The tensor renormalization group study of the general spin-S Blume-Capel model
We focus on the special situation of of the general spin-S Blume-Capel
model on the square lattice. Under the infinitesimal external magnetic field,
the phase transition behaviors due to the thermal fluctuations are discussed by
the newly developed tensor renormalization group method. For the case of the
integer spin-S, the system will undergo first-order phase transitions with
the successive symmetry breaking with the magnetization . For the
half-integer spin-S, there are similar first order phase transition
with stepwise structure, in addition, there is a continuous
phase transition due to the spin-flip symmetry breaking. In the low
temperature regions, all first-order phase transitions are accompanied by the
successive disappearance of the optional spin-component pairs(),
furthermore, the critical temperature for the nth first-order phase transition
is the same, independent of the value of the spin-S. In the absence of the
magnetic field, the visualization parameter characterizing the intrinsic
degeneracy of the different phases clearly demonstrates the phase transition
process.Comment: 6 pages, 7 figure
Surface transport coefficients for three-dimensional topological superconductors
We argue that surface spin and thermal conductivities of three-dimensional
topological superconductors are universal and topologically quantized at low
temperature. For a bulk winding number , there are "colors" of
surface Majorana fermions. Localization corrections to surface transport
coefficients vanish due to time-reversal symmetry (TRS). We argue that
Altshuler-Aronov interaction corrections vanish because TRS forbids color or
spin Friedel oscillations. We confirm this within a perturbative expansion in
the interactions, and to lowest order in a large- expansion. In both
cases, we employ an asymptotically exact treatment of quenched disorder effects
that exploits the chiral character unique to two-dimensional,
time-reversal-invariant Majorana surface states.Comment: 24 pages, 15 figures. v3: published versio
Spin-current Seebeck effect in quantum dot systems
We first bring up the concept of spin-current Seebeck effect based on a
recent experiment [Nat. Phys. {\bf 8}, 313 (2012)], and investigate the
spin-current Seebeck effect in quantum dot (QD) systems. Our results show that
the spin-current Seebeck coefficient is sensitive to different polarization
states of QD, and therefore can be used to detect the polarization state of QD
and monitor the transitions between different polarization states of QD. The
intradot Coulomb interaction can greatly enhance the due to the stronger
polarization of QD. By using the parameters for a typical QD, we demonstrate
that the maximum can be enhanced by a factor of 80. On the other hand, for
a QD whose Coulomb interaction is negligible, we show that one can still obtain
a large by applying an external magnetic field.Comment: 6 pages, 8 figure
Topological Protection from Random Rashba Spin-Orbit Backscattering: Ballistic Transport in a Helical Luttinger Liquid
The combination of Rashba spin-orbit coupling and potential disorder induces
a random current operator for the edge states of a 2D topological insulator. We
prove that charge transport through such an edge is ballistic at any
temperature, with or without Luttinger liquid interactions. The solution
exploits a mapping to a spin 1/2 in a time-dependent field that preserves the
projection along one randomly undulating component (integrable dynamics). Our
result is exact and rules out random Rashba backscattering as a source of
temperature-dependent transport, absent integrability-breaking terms.Comment: 6+3 pages, 2+1 figure
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