Parallel magnetoconductance of interacting electrons in a two-dimensional disordered system

Berkovits, Richard; Kantelhardt, Jan W.

doi:10.1103/physrevb.65.125308

Cited by 11 publications

(19 citation statements)

References 75 publications

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“…The delocalization is thus reduced by an in-plane magnetic field. All this is in accordance, at least qualitatively, with recent experimental findings 4 and numerical simulations 8,9 , regarding the in-plane magnetoresistance.…”

Section: Discussionsupporting

confidence: 92%

“…However, when taking spin into account, the situation is still unclear 5 . In a recent numerical exact-diagonalization study 8 , an Anderson model with both long range Coulomb interaction and short range Hubbard interaction was considered. It was shown that the Coulomb interaction, existing between any two electrons regardless of their spin, can only increase localization.…”

Section: Introductionmentioning

confidence: 99%

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On-site interaction effects on localization: Dominance of nonuniversal contributions

Goldstein

Berkovits

2003

Phys. Rev. B

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The influence of on-site (Hubbard) electron-electron interaction on disorder-induced localization is studied in order to clarify the role of electronic spin. The motivation is based on the recent experimental indications of a "metal-insulator" transition in two dimensional systems. We use both analytical and numerical techniques, addressing the limit of weak short-range interaction. The analytical calculation is based on Random Matrix Theory (RMT). It is found that although RMT gives a qualitative explanation of the numerical results, it is quantitatively incorrect. This is due to an exact cancellation of short range and long range correlations in RMT, which does not occur in the non-universal corrections to RMT. An estimate for these contributions is given.

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Section: Discussionsupporting

confidence: 92%

Section: Introductionmentioning

confidence: 99%

On-site interaction effects on localization: Dominance of nonuniversal contributions

Goldstein

Berkovits

2003

Phys. Rev. B

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“…The present study extends our earlier work without a magnetic field [11], in which we found clear indications that interactions enhance the conductivity and lead to metallic behavior in a temperature range (about 1/10 of the Fermi energy) similar to that of experiments. Later numerical approaches have sometimes [12][13][14][15] led to different conclusions from ours, but they either treat the problem within a Hartree-Fock method, or else use diagonalization methods which deal with considerably smaller numbers of electrons than can be studied in our approach. Very recently, an improved study using the same approach as in Ref.…”

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confidence: 99%

“…While the numerical evidence is mixed concerning the occurrence of a MIT due to interactions, there is a consensus in favor of a Zeeman magnetic field tuned transition [14,15,17,18], as we shall describe in more detail below.…”

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confidence: 99%

Interacting Electrons in a Two-Dimensional Disordered Environment: Effect of a Zeeman Magnetic Field

Denteneer

Scalettar

2003

Phys. Rev. Lett.

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The effect of a Zeeman magnetic field coupled to the spin of the electrons on the conducting properties of the disordered Hubbard model is studied. Using the Determinant Quantum Monte Carlo method, the temperature-and magnetic-fielddependent conductivity is calculated, as well as the degree of spin polarization. We find that the Zeeman magnetic field suppresses the metallic behavior present for certain values of interaction-and disorder-strength, and is able to induce a metal-insulator transition at a critical field strength. It is argued that the qualitative features of magnetoconductance in this microscopic model containing both repulsive interactions and disorder are in agreement with experimental findings in two-dimensional electron-and hole-gases in semiconductor structures.A hundred years after the Nobel prize was awarded in 1902 for the discovery of the Zeeman effect and the subsequent explanation by Lorentz, applying a magnetic field continues to be a powerful means to elucidate puzzling phenomena in nature. One of the most recent examples is the interplay of interactions and disorder in electronic systems. This field has witnessed a revival of scientific activity after pioneering experiments in low-density silicon metal-oxide-semiconductor field-effect transistors (MOSFETs) found clear indications of a metal-insulator transition (MIT) in effectively two-dimensional (2D) systems [1]. Until then, electrons in a 2D disordered environment were thought to always form an insulating phase; this mind-set was based on the scaling theory of localization for non-interacting electrons, supplemented by perturbative treatments of weak interactions, as well as studies of the limiting case of very strong interactions. The surprising phenomena were soon confirmed in other semiconductor heterostructures, although the interpretation in terms of a quantum phase transition remains controversial, and a wide variety of experimental and theoretical approaches were unleashed at the problem [2].Among these approaches is the application of magnetic fields. Contrary to the well-known effect of a magnetic field in weak-localization theory to disturb interference phenomena and hence undo localization and insulating behavior, the negative magnetoresistance effect [3], in the Si MOSFETs and similar heterostructures, the magnetic field is found to suppress the metallic behavior and therefore promote insulating behavior [4][5][6]. The effect is present for all orientations of the magnetic field relative to the 2D plane of the electrons. In particular, a Zeeman magnetic field, applied parallel to the 2D plane of electrons and therefore coupling only to the spin, and not the orbital motion of the electrons, has been used extensively. This puts into focus the important role played by the spin degree of freedom of the electron, and its polarization [7][8][9][10].In this Letter, we present a numerical study of a microscopic model for interacting electrons in a disordered environment including the effect of a Zeeman magnetic field. The presen...

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“…For example, the influence of electronelectron interactions on the persistent current and conductance has been extensively studied for small metallic clusters 14,15,16,17,18,19,20,21 . In this paper we will use exact digonalization of small clusters in order to investigate the influence of r s on χ, g and m of disordered systems.…”

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confidence: 99%

Spin polarization and effective mass: A numerical study in disordered two-dimensional systems

Berkovits¹

2004

Phys. Rev. B

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We numerically study the magnetization of small metallic clusters. The magnetic susceptibility is enhanced for lower electronic densities due to the stronger influence of electron-electron interactions. The magnetic susceptibility enhancement stems mainly from an enhancement of the mass for commensurate fillings, while for non-commensurate fillings its a result of an enhancement of the Landé g factor. The relevance to recent experimental measurements is discussed.PACS numbers: 71.10.Ca,73.43.Qt Much attention has recently been given to the study of interacting electrons in two-dimensional disordered systems, motivated by new experimental observations 1 . The conductance of dilute 2D electron systems show fascinating temperature and magnetic field dependencies. One of the most intriguing behaviors is the strong decrease in the critical magnetic field, B c , needed in order to fully spin polarize the system at low densities. These low densities are characterized by a high ratio of the intra electron interaction energy E c and the Fermi energy E F . This ratio is denoted by r s = E c /E F . In the weakly interacting regime (r s ≪ 1) the system behaves as independent non-interacting electrons with a magnetic susceptibility equal to the Pauli susceptibility χ = gµ 2 B ν (where g is the Landé factor, µ B is the Bohr magneton and ν is the density of states at the Fermi energy). As the electron density is lowered, measurements show an enhancement in the susceptibility 2,3,4,5,6,7 . Although there is an ongoing debate whether these measurements support the scenario of spontaneous spin polarization 8 , or just an enhanced magnetic susceptibility 6,7 , it is nevertheless generally accepted that a large enhancement of the magnetic susceptibility occurs over a large region of densities corresponding to r s > 6. An interesting question raised recently6,8 is whether to attribute the enhancement of susceptibility to an increase of the g factor or to an increase of the effective mass (the density of states in a 2D system is proportional to the effective mass). By a novel experimental method Pudalov et. al.6 were able to measure separately χ and m as function of r s . Although there are two different methods to extract m which do not exactly agree, nevertheless, it is clear that m increases much quicker as functions of r s than g. Recent measurements by Shashkin et. al.8 strengthen the case for a strong dependence of m on r s while g turns out to be constant. This result is in contrast to theoretical considerations based on the Fermi liquid picture which predict a strong enhancement in g 9,10,11 , but has some similarities to Wigner crystallization scenarios 12,13 .Since the development of a theoretical description of interacting electrons in disorder systems turns out to be rather intricate, a lot of effort has been invested in numerical studies. For example, the influence of electronelectron interactions on the persistent current and conductance has been extensively studied for small metallic clusters 14,15,16,17,18,19,20,21...

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Parallel magnetoconductance of interacting electrons in a two-dimensional disordered system

Cited by 11 publications

References 75 publications

On-site interaction effects on localization: Dominance of nonuniversal contributions

On-site interaction effects on localization: Dominance of nonuniversal contributions

Interacting Electrons in a Two-Dimensional Disordered Environment: Effect of a Zeeman Magnetic Field

Spin polarization and effective mass: A numerical study in disordered two-dimensional systems

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