93 research outputs found
Spin polarised scanning tunneling probe for helical Luttinger liquids
We propose a three terminal spin polarized stm setup for probing the helical
nature of the Luttinger liquid edge state that appears in the quantum spin Hall
system. We show that the three-terminal tunneling conductance strongly depends
on the angle () between the magnetization direction of the tip and the
local orientation of the electron spin on the edge while the two terminal
conductance is independent of this angle. We demonstrate that chiral injection
of an electron into the helical Luttinger liquid (which occurs when is
zero or ) is associated with fractionalization of the spin of the injected
electron in addition to the fractionalization of its charge. We also point out
a spin current amplification effect induced by the spin fractionalization.Comment: Final version to appear in Phys. Rev. Let
Probing surface states exposed by crystal terminations at arbitrary orientations of three-dimensional topological insulators
The topological properties of the bulk band structure of a three-dimensional
topological insulator (TI) manifest themselves in the form of metallic surface
states. In this paper, we propose a probe which directly couples to an exotic
property of these surface states, namely the spin-momentum locking. We show
that the information regarding the spin textures, so extracted, for different
surfaces can be put together to reconstruct the parameters characterizing the
bulk band structure of the material, hence acting as a hologram. For specific
TI materials like, , the planar surface states are distinct from one another with
regard to their spectrum and the associated spin texture for each angle
(), which the normal to the surface makes with the crystal growth axis.
We develop a tunnel Hamiltonian between such arbitrary surfaces and a spin
polarized STM which provides a unique fingerprint of the dispersion and the
associated spin texture corresponding to each . Additionally, the
theory presented in this article can be used to extract value of for a
given arbitrary planar surface from the STM spectra itself hence effectively
mimicking X-ray spectroscopy.Comment: 11 pages, 8 figures, version accepted in Phys. Rev.
Inter-edge interactions and novel fixed points at a junction of quantum Hall line junctions
We show that novel fixed points (characterized by matrices which specify the
splitting of the currents at the junction) can be accessed in a system which
contains a junction of three quantum Hall line junctions. For such a junction
of fractional quantum Hall edge states, we find that it is possible for both
the flower (single droplet) and islands (three droplets) configurations to be
stable in an intermediate region, for a range of values of the inter-edge
repulsive interactions. A measurement of the tunneling conductance as a
function of the gate voltage controlling inter-edge repulsions can give a clear
experimental signal of this region.Comment: 5 pages, 4 figure
A systematic stability analysis of the renormalisation group flow for the normal-superconductor-normal junction of Luttinger liquid wires
We study the renormalization group flows of the two terminal conductance of a
superconducting junction of two Luttinger liquid wires. We compute the power
laws associated with the renormalization group flow around the various fixed
points of this system using the generators of the SU(4) group to generate the
appropriate parameterization of a S-matrix representing small deviations from a
given fixed point S-matrix (obtained earlier in Phys. Rev. B 77, 155418
(2008)), and we then perform a comprehensive stability analysis. In particular,
for the non-trivial fixed point which has intermediate values of transmission,
reflection, Andreev reflection and crossed Andreev reflection, we show that
there are eleven independent directions in which the system can be perturbed,
which are relevant or irrelevant, and five directions which are marginal. We
obtain power laws associated with these relevant and irrelevant perturbations.
Unlike the case of the two-wire charge-conserving junction, here we show that
there are power laws which are non-linear functions of V(0) and V(2k_{F})
(where V(k) represents the Fourier transform of the inter-electron interaction
potential at momentum k). We also obtain the power law dependence of linear
response conductance on voltage bias or temperature around this fixed point.Comment: Final version to appear in Phys. Rev.
Magnetic field induced Fabry-P\'erot resonances in helical edge states
We study electronic transport across a helical edge state exposed to a
uniform magnetic ({}) field over a finite length. We show that this
system exhibits Fabry-P\'erot type resonances in electronic transport. The
intrinsic spin anisotropy of the helical edge states allows us to tune these
resonances by changing the direction of the {} field while keeping its
magnitude constant. This is in sharp contrast to the case of non-helical one
dimensional electron gases with a parabolic dispersion, where similar
resonances do appear in individual spin channels ( and )
separately which, however, cannot be tuned by merely changing the direction of
the {} field. These resonances provide a unique way to probe the
helical nature of the theory.Comment: v1: 5 pages, 5 figure
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