8,302 research outputs found
Signatures of tunable Majorana-fermion edge states
Chiral Majorana-fermion modes are shown to emerge as edge excitations in a
superconductor--topological-insulator hybrid structure that is subject to a
magnetic field. The velocity of this mode is tunable by changing the
magnetic-field magnitude and/or the superconductor's chemical potential. We
discuss how quantum-transport measurements can yield experimental signatures of
these modes. A normal lead coupled to the Majorana-fermion edge state through
electron tunneling induces resonant Andreev reflections from the lead to the
grounded superconductor, resulting in a distinctive pattern of
differential-conductance peaks.Comment: (13 pages, Accepted for publication in New Journal of Physics, an
extension of and expansion on our previous work arXiv:1210.4057). arXiv admin
note: text overlap with arXiv:1210.405
QCD Critical Point in a Quasiparticle Model
Recent theoretical investigations have unveiled a rich structure in the
quantum chromodynamics (QCD) phase diagram which consists of quark gluon plasma
(QGP) and the hadronic phases but also supports the existence of a cross-over
transition ending at a critical end point (CEP). We find a too large variation
in determination of the coordinates of the CEP in the temperature (T), baryon
chemical potential () plane and, therefore, its identification in the
current heavy-ion experiments becomes debatable. Here we use an equation of
state (EOS) for a deconfined QGP using a thermodynamically consistent
quasiparticle model involving quarks and gluons having thermal masses. We
further use a thermodynamically consistent excluded volume model for the hadron
gas (HG) which was recently proposed by us. Using these equations of state, a
first order deconfining phase transition is constructed using Gibbs' criteria.
This leads to an interesting finding that the phase transition line ends at a
critical point (CEP) beyond which a cross-over region exists. Using our thermal
HG model, we obtain a chemical freeze out curve and we find that the CEP lies
in close proximity to this curve as proposed by some authors. The coordinates
of CEP are found to lie within the reach of RHIC experiment.Comment: 15 pages, 3 figures, 1 table; minor corrections, to be appeared in
Phys. Rev.
Quantum transport signatures of chiral edge states in SrRuO
We investigate transport properties of a double quantum dot based Cooper pair
splitter, where the superconducting lead consists of SrRuO. The
proposed device can be used to explore the symmetry of the superconducting
order parameter in SrRuO by testing the presence of gapless chiral edge
states, which are predicted to exist if the bulk superconductor is described by
a chiral --wave state. The odd orbital symmetry of the bulk order parameter
ensures that we can realize a regime where the electrons tunneling into the
double dot system come from the chiral edge states and thereby leave their
signature in the conductance. The proposed Cooper pair splitter has the
potential to probe order parameters in unconventional superconductors.Comment: 5 page
Switchable valley filter based on a graphene - junction in a magnetic field
Low-energy excitations in graphene exhibit relativistic properties due to the
linear dispersion relation close to the Dirac points in the first Brillouin
zone. Two of the Dirac points located at opposite corners of the first
Brillouin zone can be chosen as inequivalent, representing a new valley degree
of freedom, in addition to the charge and spin of an electron. Using the valley
degree of freedom to encode information has attracted significant interest,
both theoretically and experimentally, and gave rise to the field of
valleytronics. We study a graphene - junction in a uniform out-of-plane
magnetic field as a platform to generate and controllably manipulate the valley
polarization of electrons. We show that by tuning the external potential giving
rise to the - junction we can switch the current from one valley
polarization to the other. We also consider the effect of different types of
edge terminations and present a setup, where we can partition an incoming
valley-unpolarized current into two branches of valley-polarized currents. The
branching ratio can be chosen by changing the location of the - junction
using a gate.Comment: 8 pages, 7 figure
- …