17,975 research outputs found
Competing pairing channels in the doped honeycomb lattice Hubbard model
Proposals for superconductivity emerging from correlated electrons in the
doped Hubbard model on the honeycomb lattice range from chiral singlet
to triplet pairing, depending on the considered range of doping and
interaction strength, as well as the approach used to analyze the pairing
instabilities. Here, we consider these scenarios using large-scale dynamic
cluster approximation (DCA) calculations to examine the evolution in the
leading pairing symmetry from weak to intermediate coupling strength. These
calculations focus on doping levels around the van Hove singularity (VHS) and
are performed using DCA simulations with an interaction-expansion
continuous-time quantum Monte Carlo cluster solver. We calculated explicitly
the temperature dependence of different uniform superconducting pairing
susceptibilities and found a consistent picture emerging upon gradually
increasing the cluster size: while at weak coupling the singlet pairing
dominates close to the VHS filling, an enhanced tendency towards -wave
triplet pairing upon further increasing the interaction strength is observed.
The relevance of these systematic results for existing proposals and ongoing
pursuits of odd-parity topological superconductivity are also discussed.Comment: 7 pages, 5 figure
Topological superconductivity at the edge of transition metal dichalcogenides
Time-reversal breaking topological superconductors are new states of matter
which can support Majorana zero modes at the edge. In this paper, we propose a
new realization of one-dimensional topological superconductivity and Majorana
zero modes. The proposed system consists of a monolayer of transition metal
dichalcogenides MX2 (M=Mo, W; X=S, Se) on top of a superconducting substrate.
Based on first-principles calculations, we show that a zigzag edge of the
monolayer MX2 terminated by metal atom M has edge states with strong spin-orbit
coupling and spontaneous magnetization. By proximity coupling with a
superconducting substrate, topological superconductivity can be induced at such
an edge. We propose NbS2 as a natural choice of substrate, and estimate the
proximity induced superconducting gap based on first-principles calculation and
low energy effective model. As an experimental consequence of our theory, we
predict that Majorana zero modes can be detected at the 120 degree corner of a
MX2 flake in proximity with a superconducting substrate
Charge-Density-Wave Transitions of Dirac Fermions Coupled to Phonons
The spontaneous generation of charge-density-wave order in a Dirac fermion
system via the natural mechanism of electron-phonon coupling is studied in the
framework of the Holstein model on the honeycomb lattice. Using two independent
and unbiased quantum Monte Carlo methods, the phase diagram as a function of
temperature and coupling strength is determined. It features a quantum critical
point as well as a line of thermal critical points. Finite-size scaling appears
consistent with fermionic Gross-Neveu-Ising universality for the quantum phase
transition, and bosonic Ising universality for the thermal phase transition.
The critical temperature has a maximum at intermediate couplings. Our findings
motivate experimental efforts to identify or engineer Dirac systems with
sufficiently strong and tunable electron-phonon coupling.Comment: 4+3 pages, 4+2 figure
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