497 research outputs found
Topological features of Haldane model on a dice lattice: role of flat band on transport properties
We study the topological properties of a Haldane model on a band deformed
dice lattice, which has three atoms per unit cell (call them as A, B and C) and
the spectrum comprises of three bands, including a flat band. The bands are
systematically deformed with an aim to study the evolution of topology and the
transport properties. The deformations are induced through hopping anisotropies
and are achieved in two distinct ways. In one of them, the hopping amplitudes
between the sites of B and C sublattices and those between A and B sublattices
are varied along a particular direction, and in the other, the hopping between
the sites of A and B sublattices are varied (keeping B-C hopping unaltered)
along the same direction. The first case retains some of the spectral features
of the familiar dice lattice and yields Chern insulating lobes in the phase
diagram with till a certain critical deformation. The topological
features are supported by the presence of a pair of chiral edge modes at each
edge of a ribbon and the plateaus observed in the anomalous Hall conductivity
support the above scenario. Whereas, a selective tuning of only the A-B hopping
amplitudes distorts the flat band and has important ramifications on the
topological properties of the system. The insulating lobes in the phase diagram
have distinct features compared to the case above, and there are dips observed
in the Hall conductivity near the zero bias. The dip widens as the hopping
anisotropy is made larger, and thus the scenario registers significant
deviation from the familiar plateau structure observed in the anomalous Hall
conductivity. However, a phase transition from a topological to a trivial
insulating region demonstrated by the Chern number changing discontinuously
from to zero beyond a certain critical hopping anisotropy remains a
common feature in the two cases
Band engineered bilayer Haldane model: Evidence of multiple topological phase transitions
We have studied the evolution of the topological properties of a
band-engineered AB-stacked bilayer honeycomb structure in the presence of a
Haldane flux. Without a Haldane flux, band engineering makes the band touching
points (the so-called Dirac points) move towards each other and eventually
merge into one at an intermediate point in the Brillouin zone.
Here the dispersion is linear along one direction and quadratic along the
other. In the presence of a Haldane flux, the system acquires topological
properties, and finite Chern numbers can be associated with the pairs of the
conduction and the valence bands. The valence band closer to the Fermi level
() possesses Chern numbers equal to and , while the one
further away from corresponds to Chern numbers . The conduction
bands are associated with similar properties, except their signs are reversed.
The Chern lobes shrink in the band-engineered model, and we find evidence of
multiple topological phase transitions, where the Chern numbers discontinuously
jump from to , to , to to and
to . These transitions are supported by the presence or absence of
the chiral edge modes in a nanoribbon bilayer geometry and the vanishing of the
plateau in the anomalous Hall conductivity. Different phases are further
computed for different hopping amplitudes across the layers, which shows the
shrinking of the Chern lobes for large interlayer tunneling
The Physiological Effect of Excessive Indulgence: Its Diagnosis, Treatment, and Prognosis
Too much of anything is bad for health. In recent years we have been familiar with “Binge”. It may be in the case of eating, drinking, or watching movies. Generation Z is very much affected by this way of living. This habit comes from indulgence. These indulgences come mainly from heredity factors, psychological conditions, dieting, peer pressure, etc. Studies show that some important features can be shared, including personality and emotional features such as neuroticism and urgency. Excessive indulgence can lead to physical and mental breakdowns. Interpersonal psychotherapy (IPT) is an effective specialty treatment for different disorders that leads to a healthy life. A continuous effort to identify the consequences of binge behaviours will also aid the development of the research field. We have to build a society free from excessive indulgence
Estimating phase transition of perturbed J1-J2 Heisenberg quantum chain in mixtures of ground and first excited states
We show that the nearest neighbour entanglement in a mixture of ground and
first excited states - the subjacent state - of the J1-J2 Heisenberg quantum
spin chain can be used as an order parameter to detect the phase transition of
the chain from a gapless spin fluid to a gapped dimer phase. We study the
effectiveness of the order parameter for varying relative mixing probabilities
between the ground and first excited states in the subjacent state for
different system sizes, and extrapolate the results to the thermodynamic limit.
We observe that the nearest neighbour concurrence can play a role of a good
order parameter even if the system is in the ground state, but with a small
probability of leaking into the first excited state. Moreover, we apply the
order parameter of the subjacent state to investigate the response to
introduction of anisotropy and of glassy disorder on the phase diagram of the
model, and analyse the corresponding finite-size scale exponents and the
emergent tricritical point.Comment: 14 pages, 9 figure
- …