Exchange effect in coupled two-dimensional electron gas systems

Ruden, P.P.; Wu, Zhiqiang

doi:10.1063/1.106116

Cited by 50 publications

(39 citation statements)

References 9 publications

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“…Apparently, the compressibility κ is negative due to the large negative contributions to the free energy from the exchange and correlation energy of a 2D electron gas [870,871], and a similar effect is predicted to occur in zero field, if the density is low enough [872]. These contributions to the Coulonb energy are both negative, and become more negative as the density increases.…”

Section: Qhementioning

confidence: 79%

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Markiewicz

1997

Journal of Physics and Chemistry of Solids

371

280

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The Van Hove singularity (VHS) provides a paradigm for the study of the role of peaks in the density of states (dos) on electronic properties. More importantly, it appears to play a major role in the physics of the high-Tc superconductors, particularly since recent photoemission studies have found that the VHS is close to the Fermi level in most of the high-Tc cuprates near the composition of optimum Tc. This paper offers a comprehensive survey of the VHS model, describing both theoretical properties and experimental evidence for the picture. Special topics discussed include a survey of the Fermi surfaces of the cuprates and related compounds, and an analysis of the reliability of the slave boson approach to correlation effects. While many properties of the cuprates can be qualitatively understood by a simple rigid-band-filling model, this is inadequate for more quantitative results, since correlation effects tend to pin the Fermi level near the VHS over an extended doping range, and can lead to a nanoscale phase separation. Furthermore, the peaks in the dos lead to competition from other instabilities, both magnetic and structural (related to charge density waves). A novel form of dynamic structural instability, involving dynamic VHS-Jahn-Teller effects has been predicted. Scattered through the literature, there is considerable experimental evidence for both nanoscale phase separation of holes, and for local, possibly dynamic, structural disorder. This review attempts to gather these results into a comprehensive database, to sort the results, and to see how they fit into the Van Hove scenario. Recent experiments on underdoped cuprates are found to provide a strong confirmation that the pseudogap is driven by a splitting of the VHS degeneracy.

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Section: Qhementioning

confidence: 79%

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Markiewicz

1997

Journal of Physics and Chemistry of Solids

371

280

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“…Deviations can be seen at low carrier densities, which are related to an increase in the disorder, which is not included in the model. Note that bistability should also be observed, as predicted by Ruden and Wu,3 due to the charge transfer, but this would require the 2DEG's to have low carrier densities, of the order of the charge transfer. Due to disorder and inhomogeneities in the sample such a low carrier density regime cannot be obtained.…”

mentioning

confidence: 73%

“…This study has led to the observation of charge transfer between the layers which was first predicted by Ruden and Wu. 3 Modeling of the device was performed by solving self-consistently the coupled Poisson and Schrödinger equations. Intralayer interactions were found to be essential to obtain good agreement with the experimental data.…”

mentioning

confidence: 99%

Exchange- and correlation-induced charge transfer observed in independently contacted triple-quantum-well structures

et al. 1996

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There have been predictions that for closely spaced two-dimensional electron gases ͑2DEG's͒, charge transfer between the 2DEG's can arise from electron interactions due to exchange and correlation ͓Ruden and Wu, Appl. Phys. Lett. 59, 2165 ͑1991͔͒. In this study, we are able to determine accurately the charge in each of the 2DEG's of a triple-quantum-well structure. The results demonstrate that as the charge in one 2DEG is reduced, by applying a negative gate voltage the adjacent layer can gain charge; thus charge is effectively transferred between the 2DEG's. This type of charge transfer cannot be explained by a simple noninteracting model of the structure, but can be modeled by including intralayer electron interactions in the form of exchange and correlation correction terms within the local-density approximation. The inclusion of these many-body interaction terms into our model leads to a good qualitative agreement with the experimental data, confirming that the origin of the charge transfer is electron interactions.

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“…Following calculations in refs. 42,43 , using a classical estimate of a single-layer Wigner crystal cohesive energy, and neglecting the kinetic energy since both layers are considered in the lowest Landau level, we find the capacitive model can underestimate the the p T OT at which the the bottom layer is completely depleted by as much as 1 × 10 10 cm −2 . (c) Spectra, real diagonal conductivity Re (σxx) vs frequency, f , from sample M465.…”

Section: Experimental Methodsmentioning

confidence: 99%

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

et al. 2012

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We report studies of pinning mode resonances of magnetic field induced bilayer Wigner crystals of bilayer hole samples with negligible interlayer tunneling and different interlayer separations d, in states with varying layer densities, including unequal layer densities. With unequal layer densities, samples with large d relative to the in-plane carrier-carrier spacing a, two pinning resonances are present, one for each layer. For small d/a samples, a single resonance is observed even with significant density imbalance. These samples, at balance, were shown to exhibit an enhanced pinning mode frequency [Zhihai Wang et al., Phys. Rev. Lett. 136804 (2007)], which was ascribed to a onecomponent, pseudospin ferromagnetic Wigner solid. The evolution of the resonance frequency and line width indicates the quantum interlayer coherence survives at moderate density imbalance, but disappears when imbalance is sufficiently large.

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Exchange effect in coupled two-dimensional electron gas systems

Cited by 50 publications

References 9 publications

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

A survey of the Van Hove scenario for high-tc superconductivity with special emphasis on pseudogaps and striped phases

Exchange- and correlation-induced charge transfer observed in independently contacted triple-quantum-well structures

Unequal layer densities in bilayer Wigner crystal at high magnetic fields

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