Chemistry Reference
In-Depth Information
stabilizes the honeycomb structure will maintain the structural integrity
of graphene. A recent article reviews
[
57
]
theoretical study of doping in
graphene.
The discovery of time reversal symmetry braking
order
[
40
]
for the
superconducting state, within our RVB mechanism is very interesting. This
unconventional order parameter has its own signatures in several physical
properties: (i) spontaneous currents in domain walls, (ii) chiral domain wall
states (iii) unusual vortex structure and (iv) large magnetic fields arising
from the
d
+
id
d
= 2 angular momentum of the cooper pairs, which could be
detected
SR measurements. Suggestions for experimental determination
of such an order by means of Andreev conductance spectra have been made
[
58
]
.
There are also several theoretical and experimental issues that needs to
be addressed. It is known that graphene realized in experimental systems
contains, adsorbed species, inhomogeneities, curvature, ripples etc. [59]
Is the superconducting ground state stable to these “perturbations”? In
particular our theory gives a substantial ODLRO even for small doping. If
disorder effects are indeed suppressing a fragile Kosterlitz-Thouless order
in the currently available doping regime in real systems, one could uncover
the hidden superconductivity by disorder control or study of cooper pair
fluctuation effects. Further analysis is necessary to address these issues.
µ
5. Composite Fermi Sea
Composite fermion
is a remarkable discovery
[
60; 61; 62
]
, made in the con-
text of fractional quantum Hall effect. A bare electron in the lowest Landau
level gets attached to an integer number of quantized fluxes. When the
number of bound flux quanta is even the composite particle is a fermion
andiscalleda
composite fermion
. This concept helps in unifying an en-
tire gamut of fractional Hall states and also has important consequences.
In particular, for the the half filled Landau level, one has an unexpected
composite fermi sea as a normal (reference) state. It is natural to look
for composite fermi sea in graphene. In particular, neutral graphene in a
magnetic field has two Landau levels that are half filled (in the absence of
spin polarization). Will these half filled states lead to a composite fermi
sea? In a recent theoretical work we provided
[
63
]
an armative answer.
In comparision to standard 2d electron gas provided by inversion layers
and heterostructures, the 2d electron gas in graphene is special. As we saw
earlier the Landau spectrum scales as
√
n
, the Landau level index. At zero
