Metal-Insulator Transition in Two Dimensions: Effects of Disorder and Magnetic Field

Popović, Dragana; Fowler, A. B.; Washburn, S.

doi:10.1103/physrevlett.79.1543

Cited by 256 publications

(262 citation statements)

References 15 publications

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“…71-73 is for Si-MOSFET samples. The data for GaAs heterostructures, and Si in other geometries is qualitatively similar [120,62,63,210,119,184]. Fig.…”

Section: Methodssupporting

confidence: 65%

Singular or non-Fermi liquids

2002

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“…71-73 is for Si-MOSFET samples. The data for GaAs heterostructures, and Si in other geometries is qualitatively similar [120,62,63,210,119,184]. Fig.…”

Section: Methodssupporting

confidence: 65%

Singular or non-Fermi liquids

2002

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“…A high magnetic field of 9 T parallel to the 2D plane drastically increases ρ xx and eliminates the positive temperature dependence even in the low-ρ xx region [14]. The disappearance of the MIT due to the parallel magnetic field seems to resemble that induced by increasing disorder reported by Popović et al [2].In non-interacting degenerate 2D Fermi gases, the spin polarization p increases linearly with the total strength B tot of the magnetic field for p < 1 and reaches p = 1 at the critical magnetic field of B c = 2πh 2 N s /µ B g v g * m * . Here, µ B is the Bohr magneton (=he/2m e ).…”

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confidence: 69%

“…By rotating the sample at various total strength of the magnetic field, we found that the normal component of the magnetic field at minima in the diagonal resistivity increases linearly with the concentration of "spin-up" electrons. 71.30.+h, 73.40.Qv, 73.40.Hm A metal-insulator transition (MIT) observed in Si metal-oxide-semiconductor field-effect transistors [1,2] (Si-MOSFET's) and other systems [3-6] attracts a great deal of attention since it seems to contradict an important result of the scaling theory by Abrahams et al [7] that the conductance of a disordered two-dimensional (2D) system at zero magnetic field goes to zero for T → 0. In the metallic phase in Si-MOSFET's with high peak electron mobilities of µ peak > ∼ 2 m 2 /V s, the diagonal resistivity ρ xx shows a sharp drop with decreasing temperature from about 2 K [1].…”

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confidence: 99%

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Spin Degree of Freedom in a Two-Dimensional Electron Liquid

et al. 1999

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We have investigated correlation between spin polarization and magnetotransport in a high mobility silicon inversion layer which shows the metal-insulator transition. Increase in the resistivity in a parallel magnetic field reaches saturation at the critical field for the full polarization evaluated from an analysis of low-field Shubnikov-de Haas oscillations. By rotating the sample at various total strength of the magnetic field, we found that the normal component of the magnetic field at minima in the diagonal resistivity increases linearly with the concentration of "spin-up" electrons. 71.30.+h, 73.40.Qv, 73.40.Hm A metal-insulator transition (MIT) observed in Si metal-oxide-semiconductor field-effect transistors [1,2] (Si-MOSFET's) and other systems [3-6] attracts a great deal of attention since it seems to contradict an important result of the scaling theory by Abrahams et al. [7] that the conductance of a disordered two-dimensional (2D) system at zero magnetic field goes to zero for T → 0. In the metallic phase in Si-MOSFET's with high peak electron mobilities of µ peak > ∼ 2 m 2 /V s, the diagonal resistivity ρ xx shows a sharp drop with decreasing temperature from about 2 K [1]. Recent experiments [8,9] show that magnetic fields applied parallel to the 2D plane suppress the low temperature metallic conduction in Si-MOSFET's. Since the parallel magnetic field does not couple the orbital motion of electrons, this fact suggests an important role of the spin of electrons. However, the mechanism of the conduction in the anomalous metallic phase is not clear yet.The 2D systems that show the MIT [1-6] are characterized by strong Coulomb interaction between electrons. The mean Coulomb energy per electron U = (πN s ) 1/2 e 2 /4πε 0 κ is larger than the mean kinetic energy K = πh 2 N s /m * by an order of the magnitude around the critical point for the MIT. Here, N s is the electron concentration, κ is the relative dielectric constant at the interface, and m * is the effective mass of electron. It is estimated that U = 120 K, K = 14 K and the ratio r s = U/K = 8.3 for κ = 7.7 and m * = 0.19m e at N s = 1 × 10 15 m −2 in Si-MOSFET's. The ground state of the insulating phase of high mobility Si-MOSFET's is considered to be a pinned Wigner solid (WS) [10,11]. Magnetic field dependence of the thermal activation energy observed for various angles of the magnetic field was essentially explained by a model based on magnetic interactions in the pinned WS [12,13]. Although the quantum fluctuations change the 2D system into a liquid at higher-N s , electron-electron (e-e) interaction is expected to be still important.In the conduction band of silicon, the spin-orbit interaction is negligible and the spin polarization p = (N ↑ − N ↓ )/N s can always be given in the direction to the magnetic field. Here N ↑ and N ↓ are the concentrations of electrons having an up spin and a down spin, respectively (N s = N ↑ + N ↓ ). In the present work, we investigate the low temperature conduction in a high mobility Si-MOSFET for vario...

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“…If the interaction becomes stronger it eventually reduces the conductance also in the localized regime. Let us finally mention that although we show that interactions can enhance the conductivity in certain parameter regions this does not directly provide an explanation for the MIT in 2D [3] since the importance of the spin degrees of freedom for this transition is established experimentally [26]. We emphasize however, that our method is very easy to generalize to electrons with spin.…”

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Do Interactions Increase or Reduce the Conductance of Disordered Electrons? It Depends!

1998

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We investigate the influence of electron-electron interactions on the conductance of two-dimensional disordered spinless electrons. We present an efficient numerical method based on diagonalization in a truncated basis of Hartree-Fock states to determine with high accuracy the low-energy properties in the entire parameter space. We find that weak interactions increase the d.c. conductance in the strongly localized regime while they decrease the d.c. conductance for weak disorder. Strong interactions always decrease the conductance. We also study the localization of single-particle excitations at the Fermi energy which turns out to be only weakly influenced by the interactions. 71.55.Jv, 72.15.Rn, 71.30.+h The influence of electron-electron interactions on the transport in disordered electronic systems has been investigated intensively within the last two decades [1,2]. Recently, the problem has reattracted a lot of attention after experimental [3] and theoretical [4] results challenged established opinions.It is well accepted [5] that non-interacting electrons in three dimensions (3D) undergo a localizationdelocalization transition at finite disorder. In contrast, all states are localized in 2D and 1D even for infinitesimal weak disorder [6]. However, today it is believed that the metal-insulator transition (MIT) in most experimental systems cannot be explained based on noninteracting electrons. The metallic phase of disordered interacting electrons has been studied intensively within the perturbative renormalization group (RG) [2] leading to a qualitative analysis of the MIT and the identification of different universality classes. One of the results is that the lower critical dimension of the MIT is d − c = 2 as it is for non-interacting electrons. Therefore it came as a surprise when experiments [3] on Si-MOSFETs revealed indications of a MIT in 2D. Since these experiments are performed at low electron density where the Coulomb interaction is particularly strong compared to the Fermi energy, interaction effects are a likely reason for this MIT. A complete understanding has, however, not yet been obtained. Explanations were suggested based on the perturbative RG [7], non-perturbative effects [8], or the transition being a superconductor-insulator transition rather than a MIT [9].Theoretically, surprising results have been obtained for just two interacting particles in the insulating regime [4]. It was found that two particles can form a pair whose localization length is much larger than that of a single particle. Later an even larger delocalization was suggested for clusters of three or more particles [10]. In the case of a repulsive electron-electron these delocalized states have rather high energy, thus their relevance for the low-energy properties of a degenerate system is not clear. It has been argued that the many-particle problem can be reduced to a few interacting quasiparticles above the Fermi surface [11]. This is, however, only possible, if the interactions do not change the nature of the ground s...

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Metal-Insulator Transition in Two Dimensions: Effects of Disorder and Magnetic Field

Cited by 256 publications

References 15 publications

Singular or non-Fermi liquids

Singular or non-Fermi liquids

Spin Degree of Freedom in a Two-Dimensional Electron Liquid

Do Interactions Increase or Reduce the Conductance of Disordered Electrons? It Depends!

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