Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields

Manolescu, Andrei; Gerhardts, Rolf R.

doi:10.1103/physrevb.56.9707

Cited by 30 publications

(38 citation statements)

References 33 publications

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“…1. Such snaking states were studied earlier in the 90's in a planar electron gas in a perpendicular magnetic field with alternating sign [36][37][38] and found responsible for strong positive magnetoresistance in the presence of ferromagnetic microstrips [39,40]. For our above-mentioned tubular nanowire the snaking states become ground states at nonzero wave vector, imposing a nonmonotonic energy dispersion.…”

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confidence: 52%

Reversal of Thermoelectric Current in Tubular Nanowires

et al. 2017

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We calculate the charge current generated by a temperature bias between the two ends of a tubular nanowire. We show that in the presence of a transversal magnetic field the current can change sign, i.e., electrons can either flow from the hot to the cold reservoir, or in the opposite direction, when the temperature bias increases. This behavior occurs when the magnetic field is sufficiently strong, such that Landau and snaking states are created, and the energy dispersion is nonmonotonic with respect to the longitudinal wave vector. The sign reversal can survive in the presence of impurities. We predict this result for core/shell nanowires, for uniform nanowires with surface states due to the Fermi level pinning, and for topological insulator nanowires. PACS numbers: 73.23.b, 73.50.Lw, 73.63.Nm, 73.50.Fqi A temperature gradient across a conducing material induces an energy gradient, which in turn results in particle transport. In an open circuit, where no net current flows, a voltage is then generated when two ends of a sample are maintained at different temperatures -this is the Seebeck effect and the linear voltage response is known as thermopower. The hotter particles have larger average kinetic energy, and the net particle flow is therefore generally from the hot to the cold side. The thermopower and thermoelectric current can be positive or negative, depending on the type of charge carriers, i.e., electrons or holes.In comparison to this macroscopic case, the thermopower at the nanoscale has special characteristics. For example, if the energy separation between the quantum states of the system is larger than the thermal energy the thermopower may alternate between positive and negative values, depending on the position of the Fermi level relatively to a resonant energy, which can be controlled with a gate voltage. These oscillations were predicted a long time ago [1], and subsequently experimentally observed in quantum dots [2][3][4], and in molecules [5]. A sign change in the thermopower can also be obtained by increasing the temperature gradient and thus the population of the resonant level [6][7][8][9]. In these examples the charge carriers are electrons and the sign change of the thermopower means that they travel from the cold side to the hot side, which may appear counterintuitive. Other nonlinear effects can occur if the characteristic relaxation length of electrons and or phonons exceeds the sample size [10], because the energy of electrons and/or phonons is no longer controlled by the temperature of the bath, but by the generated electric bias, including Coulomb interactions [11,12].Observing such negative thermopower at the nanoscale is difficult for at least two reasons: the currents tend to be small and it is hard to maintain a constant temperature difference across such short distances. Here we argue that a generic class of tubular nanowires, to be defined in more detail below, are ideal systems for both realizing and observing negative thermopower. Semiconductor nanowires are versatile syst...

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Reversal of Thermoelectric Current in Tubular Nanowires

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“…The limiting point at d W = 0 (2DEG) was calculated with equation (16) and the remaining points with equation (14). The excellent match between these two different equations reflects the correctness of our derivations and calculations [13].…”

Section: B Resultsmentioning

confidence: 99%

“…Thus, we have dressed the interaction line of the exchange diagram [14] by replacing the bare Coulomb potential V (q = |k − k'|) = (2πe 2 /ε)(1/q) in equation (8) with the statically screened Coulomb potential…”

Section: Screened-hartree-fock Theory With Polarization-independementioning

confidence: 99%

Spontaneous spin polarization in doped semiconductor quantum wells

Juri

Tamborenea

2005

Eur. Phys. J. B

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We calculate the critical density of the zero-temperature, first-order ferromagnetic phase transition in n-doped GaAs/AlGaAs quantum wells. We find that the existence of the ferromagnetic transition is dependent upon the choice of well width. We demonstrate rigorously that this dependence is governed by the interplay between different components of the exchange interaction and that there exists an upper limit for the well width beyond which there is no transition. We predict that some narrow quantum wells could exhibit this transition at electron densities lower than the ones that have been considered experimentally thus far. We use a screened Hartree-Fock approximation with a polarization-dependent effective mass, which is adjusted to match the critical density predicted by Monte Carlo calculations for the two-dimensional electron gas.

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“…5. In the case of weak spatial fluctuations of the effective potential, we have derived the estimation (72) for the spin splitting between the first energy levels, which can be further simplified for a very smooth disorder potential by using expansion (51). As a result, we can directly correlate the spatial variations δE s (R) of this spin splitting E s with the bare disorder potential ] as a function of the energy E for the three tip positions defined in Fig.…”

Section: Analysis Of Local Spin Splitting In Sts Experiments With mentioning

confidence: 99%

“…redistribution of the electron density at the Fermi level, leading to the formation in the sample of alternating compressible and incompressible regions of different widths at high magnetic fields 47,48 . Note that, in principle, it is necessary to include both direct and exchange interactions between electrons in order to microscopically determine the total scalar potential [49][50][51] .…”

Section: Green's Function Formalism For Disordered Quantum Hall Smentioning

confidence: 99%

Spectral properties and local density of states of disordered quantum Hall systems with Rashba spin-orbit coupling

Hernangómez‐Pérez¹,

Ulrich²,

Florens³

et al. 2013

Phys. Rev. B

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We theoretically investigate the spectral properties and the spatial dependence of the local density of states (LDoS) in disordered two-dimensional electron gases (2DEG) in the quantum Hall regime, taking into account the combined presence of electrostatic disorder, random Rashba spin-orbit interaction, and finite Zeeman coupling. To this purpose, we extend a coherent-state Green's function formalism previously proposed for spinless 2DEG in the presence of smooth arbitrary disorder, that here incorporates the nontrivial coupling between the orbital and spin degrees of freedom into the electronic drift states. The formalism allows us to obtain analytical and controlled nonperturbative expressions of the energy spectrum in arbitrary locally flat disorder potentials with both random electric fields and Rashba coupling. As an illustration of this theory, we derive analytical microscopic expressions for the LDoS in different temperature regimes which can be used as a starting point to interpret scanning tunneling spectroscopy data at high magnetic fields. In this context, we study the spatial dependence and linewidth of the LDoS peaks and explain an experimentally-noticed correlation between the spatial dispersion of the spin-orbit splitting and the local extrema of the potential landscape.

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Coulomb effects on the quantum transport of a two-dimensional electron system in periodic electric and magnetic fields

Cited by 30 publications

References 33 publications

Reversal of Thermoelectric Current in Tubular Nanowires

Reversal of Thermoelectric Current in Tubular Nanowires

Spontaneous spin polarization in doped semiconductor quantum wells

Spectral properties and local density of states of disordered quantum Hall systems with Rashba spin-orbit coupling

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