Electron correlations in charge coupled vertically stacked quantum rings

Szafran, B.; Bednarek, S.; Dudziak, M.

doi:10.1103/physrevb.75.235323

Cited by 15 publications

(17 citation statements)

References 33 publications

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“…Exact results are compared to the ones obtained with the best separable wave function provided by the Hartree approach, which is a natural point of reference to study the quantum correlations present only in the exact ͑en-tangled͒ wave function and is a starting point to the density functional calculations. A previous study performed for vertical rings 22 indicated that the Hartree approximation produces charge densities of an artifactal broken symmetry. In laterally coupled rings that are studied in the present paper, the circular symmetry breaking is real and Hartree approach turns out to be nearly exact for the ground state.…”

Section: Introductionmentioning

confidence: 96%

“…Persistent currents in quantum rings attracted a lot of attention, but the theoretical work 7,12-16 addressed a single semiconductor quantum ring and not multiple rings laterally coupled by the Coulomb interaction. Coulomb and tunnel coupling was extensively studied [17][18][19][20][21][22][23][24] for ring molecules produced in concentric [25][26][27] and vertical 28 configurations. Recently, states of a single electron in a pair of coplanar rings situated side by side were also studied.…”

Section: Introductionmentioning

confidence: 99%

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Charged coplanar semiconductor quantum rings: Magnetization and inter-ring electron-electron correlation

Szafran

2008

Phys. Rev. B

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We study a coplanar system of electrostatically coupled semiconductor quantum rings each charged by a single electron using a configuration-interaction approach. We find that the electron densities confined in separate rings are significantly deformed by the inter-ring coupling which results in reduction of the persistent currents and the magnetic dipole moments that they generate, particularly at half flux quanta for which the persistent current loops are broken by appearance of zeros of angular single-ring wave functions. For three and more rings, the magnetic properties of the system strongly depend on the geometry of the ring configuration. We demonstrate a frustration mechanism which prevents the charge density deformation and reduction of the magnetization that occurs for rings near symmetry centers of the system. Due to this mechanism, the average magnetization produced by a linear array of rings exceeds several times the one generated by a square array. We discuss the nature of the electron-electron spatial inter-ring correlation. In the ground state, the correlation is semiclassical and can be reproduced by a separable wave function. Quantum correlation is weak and short range in the ground state. Excited states with longer range zigzag correlated structures formed in the internal degrees of freedom are also discussed.

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Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Charged coplanar semiconductor quantum rings: Magnetization and inter-ring electron-electron correlation

Szafran

2008

Phys. Rev. B

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“…37 In addition, the spatial correlation between electron pairs in vertically stacked QRs has been shown to undergo oscillations as functions of the magnetic flux, with strongly correlated situations between ground states ͑gs's͒ with odd angular momentum turning out to occur even at large inter-ring distances. 34 More recently, the structure of a QRM made of two vertically stacked quantum rings has been addressed at zero magnetic field for a few tens of electrons within the local spin-density-functional theory ͑LSDFT͒ neglecting 38 and incorporating 39 the vertical thickness of the constituent QRs.…”

Section: Introductionmentioning

confidence: 99%

Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields

et al. 2008

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Vertically coupled double quantum rings submitted to a perpendicular magnetic field B are addressed within the local spin-density-functional theory. We describe the structure of quantum ring molecules containing up to 40 electrons considering different inter-ring distances and intensities of the applied magnetic field. When the rings are quantum mechanically strongly coupled, only bonding states are occupied and the addition spectrum of the artificial molecules resembles that of a single-quantum ring, with some small differences appearing as an effect of the magnetic field. Despite the latter's tendency to flatten the spectra, in the strong-coupling limit, some clear peaks are still found even when B 0 that can be interpretated from the single-particle energy levels similarly as in the zero magnetic field case, namely, in terms of closed-shell and Hund's-rule configurations. By increasing the inter-ring distance, the occupation of the first antibonding orbitals washes out such structures and the addition spectra become flatter and irregular. In the weak-coupling regime, numerous isospin oscillations are found as functions of B.

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“…(6) does not affect any of the results presented below due to the complete separability of the electron wave functions. 27 For that reason we skipped the anti-symmetrization in the following.…”

Section: Theorymentioning

confidence: 99%

Carrier-carrier inelastic scattering events for spatially separated electrons: Magnetic asymmetry and turnstile electron transfer

Poniedziałek

Szafran

2012

Phys. Rev. B

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We consider a single electron traveling along a strictly one-dimensional quantum wire interacting with another electron in a quantum ring capacitively coupled to the wire. We develop an exact numerical method for treating the scattering problem within the stationary two-electron wave function picture. The considered process conserves the total energy but the electron within the wire passes a part of its energy to the ring. We demonstrate that the inelastic scattering results in both magnetic asymmetry of the transfer probability and a turnstile action of the ring on the electrons traveling separately along the ring. We demonstrate that the inelastic backscattering and / or inelastic electron transfer can be selectively eliminated from the process by inclusion of an energy filter into the wire in form of a double barrier system with the resonant energy level tuned to the energy of the incident electron. We demonstrate that the magnetic symmetry is restored when the inelastic backscattering is switched off, and the turnstile character of the ring is removed when the energy transfer to the ring is excluded for both transferred and backscattered electron waves. We discuss the relation of the present results to the conductance systems based on the electron gas.

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Electron correlations in charge coupled vertically stacked quantum rings

Cited by 15 publications

References 33 publications

Charged coplanar semiconductor quantum rings: Magnetization and inter-ring electron-electron correlation

Charged coplanar semiconductor quantum rings: Magnetization and inter-ring electron-electron correlation

Isospin phases of vertically coupled double quantum rings under the influence of perpendicular magnetic fields

Carrier-carrier inelastic scattering events for spatially separated electrons: Magnetic asymmetry and turnstile electron transfer

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