Abstract
We study the effect of interlayer Coulomb interaction in an electronic double layer. Assuming that each of the layers consists of a bipartite lattice, a sufficiently strong interlayer interaction leads to an interlayer pairing of electrons with a staggered order parameter. We show that the correlated pairing state is dual to the excitonic pairing state with uniform order parameter in an electron-hole double layer. The interlayer pairing of electrons leads to strong current-current correlations between the layers. We also analyze the interlayer conductivity and the fluctuations of the order parameter, which consists of a gapped and a gapless mode.
Highlights
Layered electronic systems have attracted substantial attention over several decades because new physical effects can be observed, which neither exist in a single layer nor in an isotropic three-dimensional systems
Interlayer tunneling is ignored here to demonstrate only the effect of the interlayer Coulomb interaction. It may have some effect on the form of the order parameter though, as it was observed in the case of an attractive interlayer Coulomb interaction [19]
This implies that we do not expect the formation of excitonic Cooper pairs but a collective state built by electron pairs in the two layers, provided the Coulomb interaction is strong enough and the thermal fluctuations are weak at sufficiently low temperatures
Summary
As a possible ansatz for the local-order parameter we consider a staggered order parameter with opposite signs on the two sublattices:. In the staggered order parameter we can replace (−1) j by a general phase factor exp(iφ j ) with some phases φ j It turns out, though, that only φ j = π j gives a stable mean-field solution. To obtain the value of we solve the mean-field equation δ F = 0 E2 + 2 where ρ(E ) is the density of states (DOS) The solution of this equation provides us the value of as a function of the temperature and the coupling strength g.
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