295,645 research outputs found
Weak coupling limits in a stochastic model of heat conduction
We study the Brownian momentum process, a model of heat conduction, weakly
coupled to heat baths. In two different settings of weak coupling to the heat
baths, we study the non-equilibrium steady state and its proximity to the local
equilibrium measure in terms of the strength of coupling. For three and four
site systems, we obtain the two-point correlation function and show it is
generically not multilinear.Comment: 18 page
Superconductivity of disordered Dirac fermions
We study the effect of disorder on massless, spinful Dirac fermions in two
spatial dimensions with attractive interactions, and show that the combination
of disorder and attractive interactions is deadly to the Dirac semimetal phase.
First, we derive the zero temperature phase diagram of a clean Dirac fermion
system with tunable doping level ({\mu}) and attraction strength (g). We show
that it contains two phases: a superconductor and a Dirac semimetal. Then, we
show that arbitrarily weak disorder destroys the Dirac semimetal, turning it
into a superconductor. We discuss the strength of the superconductivity for
both long range and short range disorder. For long range disorder, the
superconductivity is exponentially weak in the disorder strength. For short
range disorder, a uniform mean field analysis predicts that superconductivity
should be doubly exponentially weak in the disorder strength. However, a more
careful treatment of mesoscopic fluctuations suggests that locally
superconducting puddles should form at a much higher temperature, and should
establish global phase coherence at a temperature that is only exponentially
small in weak disorder. We also discuss the effect of disorder on the quantum
critical point of the clean system, building in the effect of disorder through
a replica field theory. We show that disorder is a relevant perturbation to the
supersymmetric quantum critical point. We expect that in the presence of
attractive interactions, the flow away from the critical point ends up in the
superconducting phase, although firm conclusions cannot be drawn since the
renormalization group analysis flows to strong coupling. We argue that although
we expect the quantum critical point to get buried under a superconducting
phase, signatures of the critical point may be visible in the finite
temperature quantum critical regime.Comment: Added some discussion, particularly pertaining to proximity effec
Avoided Critical Behavior in a Uniformly Frustrated System
We study the effects of weak long-ranged antiferromagnetic interactions of
strength on a spin model with predominant short-ranged ferromagnetic
interactions. In three dimensions, this model exhibits an avoided critical
point in the sense that the critical temperature is strictly greater
than . The behavior of this system at temperatures less
than is controlled by the proximity to the avoided critical point.
We also quantize the model in a novel way to study the interplay between
charge-density wave and superconducting order.Comment: 32 page Latex file, figures available from authors by reques
Boosting proximity spin orbit coupling in graphene/WSe heterostructures via hydrostatic pressure
Van der Waals heterostructures composed of multiple few layer crystals allow
the engineering of novel materials with predefined properties. As an example,
coupling graphene weakly to materials with large spin orbit coupling (SOC)
allows to engineer a sizeable SOC in graphene via proximity effects. The
strength of the proximity effect depends on the overlap of the atomic orbitals,
therefore, changing the interlayer distance via hydrostatic pressure can be
utilized to enhance the interlayer coupling between the layers. In this work,
we report measurements on a graphene/WSe heterostructure exposed to
increasing hydrostatic pressure. A clear transition from weak localization to
weak anti-localization is visible as the pressure increases, demonstrating the
increase of induced SOC in graphene
Boosting proximity spin orbit coupling in graphene/WSe2 heterostructures via hydrostatic pressure
Van der Waals heterostructures composed of multiple few layer crystals allow the engineering of novel materials with predefined properties. As an example, coupling graphene weakly to materials with large spin orbit coupling (SOC) allows to engineer a sizeable SOC in graphene via proximity effects. The strength of the proximity effect depends on the overlap of the atomic orbitals, therefore, changing the interlayer distance via hydrostatic pressure can be utilized to enhance the interlayer coupling between the layers. In this work, we report measurements on a graphene/WSe2 heterostructure exposed to increasing hydrostatic pressure. A clear transition from weak localization to weak anti-localization is visible as the pressure increases, demonstrating the increase of induced SOC in graphene
Proximity-induced topological transition and strain-induced charge transfer in graphene/MoS2 bilayer heterostructures
Graphene/MoS2 heterostructures are formed by combining the nanosheets of
graphene and monolayer MoS2. The electronic features of both constituent
monolayers are rather well-preserved in the resultant heterostructure due to
the weak van der Waals interaction between the layers. However, the proximity
of MoS2 induces strong spin orbit coupling effect of strength ~1 meV in
graphene, which is nearly three orders of magnitude larger than the intrinsic
spin orbit coupling of pristine graphene. This opens a bandgap in graphene and
further causes anticrossings of the spin-nondegenerate bands near the Dirac
point. Lattice incommensurate graphene/MoS2 heterostructure exhibits
interesting moire' patterns which have been observed in experiments. The
electronic bandstructure of heterostructure is very sensitive to biaxial strain
and interlayer twist. Although the Dirac cone of graphene remains intact and no
charge-transfer between graphene and MoS2 layers occurs at ambient conditions,
a strain-induced charge-transfer can be realized in graphene/MoS2
heterostructure. Application of a gate voltage reveals the occurrence of a
topological phase transition in graphene/MoS2 heterostructure. In this chapter,
we discuss the crystal structure, interlayer effects, electronic structure,
spin states, and effects due to strain and substrate proximity on the
electronic properties of graphene/MoS2 heterostructure. We further present an
overview of the distinct topological quantum phases of graphene/MoS2
heterostructure and review the recent advancements in this field.Comment: 31 pages, 12 figure
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