Metal-insulator transition of isotopically enriched neutron-transmutation-doped<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msup><mml:mrow /><mml:mrow><mml:mn>70</mml:mn></mml:mrow></mml:msup></mml:mrow><mml:mi mathvariant="normal">Ge</mml:mi><mml:mo>:</mml:mo><mml:mi mathvariant="normal">Ga</mml:mi></mml:math>in magnetic fields

Watanabe, Michio; Itoh, Kohei M.; Ootuka, Youiti; Häller, E. E.

doi:10.1103/physrevb.60.15817

Cited by 12 publications

(13 citation statements)

References 27 publications

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“…This similarity probably results from the general expectation of a power-law shift of n c with B in the case of a true MIT [6]. Such a shift has been observed also in several 3D systems [28,[54][55][56].…”

Section: Effects Of Magnetic Fieldsupporting

confidence: 64%

Chapter 5. Metal-Insulator Transition in Correlated Two-Dimensional Systems with Disorder

Popović¹

2016

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Experimental evidence for the possible universality classes of the metal-insulator transition (MIT) in two dimensions (2D) is discussed. Sufficiently strong disorder, in particular, changes the nature of the transition. Comprehensive studies of the charge dynamics are also reviewed, describing evidence that the MIT in a 2D electron system in silicon should be viewed as the melting of the Coulomb glass. Comparisons are made to recent results on novel 2D materials and quasi-2D strongly correlated systems, such as cuprates. I. 2D METAL-INSULATOR TRANSITION AS A QUANTUM PHASE TRANSITIONThe metal-insulator transition (MIT) in 2D systems remains one of the most fundamental open problems in condensed matter physics [1][2][3][4]. The very existence of the metal and the MIT in 2D had been questioned for many years but, recently, considerable experimental evidence has become available in favor of such a transition. Indeed, in the presence of electron-electron interactions, the existence of the 2D MIT does not contradict any general idea or principle (see also chapters by V. Dobrosavljević, and A. A. Shashkin and S. V. Kravchenko). It is important to recall that a qualitative distinction between a metal and an insulator exists only at temperature T = 0: the conductivity σ(T = 0) = 0 in the metal, and σ(T = 0) = 0 in the insulator. Therefore, the MIT is an example of a quantum phase transition (QPT) [5]: it s a continuous phase transition that occurs at T = 0, i.e. between two ground states. It is controlled by some parameter of the Hamiltonian of the system, such as carrier density, the external magnetic field, or pressure, and quantum fluctuations dominate the critical behavior. In analogy to thermal phase transitions, a QPT is characterized by a correlation length ξ ∝ |δ| −ν and the corresponding timescale τ ξ ∼ ξ z , both of which diverge in a power-law fashion at the critical point. Here δ is a dimensionless (reduced) distance of a control parameter from its critical value, ν is the correlation length exponent and z is the dynamical exponent. Because of the Heisenberg uncertainty principle, in a QPT there is a characteristic energy (temperature) scale

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Section: Effects Of Magnetic Fieldsupporting

confidence: 64%

Chapter 5. Metal-Insulator Transition in Correlated Two-Dimensional Systems with Disorder

Popović¹

2016

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“…Therefore, comparison of µ with and without the time-reversal symme-try, i.e., with and without external magnetic fields becomes important. We study the MIT of 70 Ge:Ga in magnetic fields up to B = 8 T and show that µ changes from 0.5 at B = 0 to 1.1 at B ≥ 4 T [20]. The same exponent µ ′ = 1.1 is also found in the magnetic-field-tuned MIT for three different samples, i.e.,…”

Section: Introductionsupporting

confidence: 55%

Metal-Insulator Transition in Homogeneously Doped Germanium

Watanabe

Fundamental Materials Research

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“…The key features of the n c (B) phase diagram have been reproduced theoretically based on a scenario of quantum melting of a Wigner crystal as the mechanism of the MIT in sufficiently clean samples (Camjayi et al, 2008). In general, a power-law shift of n c with B is expected to occur in the case of a true MIT , and has been observed in several 3D systems (Rosenbaum et al, 1989;Bogdanovich et al, 1997;Sarachik et al, 1998;Watanabe et al, 1999).…”

Section: D Metal-insulator Transition In a Parallel Magnetic Fieldmentioning

confidence: 87%

Glassy Dynamics of Electrons Near the Metal–Insulator Transition

Popović¹

2012

Conductor-Insulator Quantum Phase Transitions

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PrefaceThis review first describes the evidence that strongly suggests the existence of the metal-insulator transition (MIT) in a two-dimensional electron system in Si regardless of the amount of disorder. Extensive studies of the charge dynamics demonstrate that this transition is closely related to the glassy freezing of electrons as temperature T → 0. Similarities to the behavior of three-dimensional materials raise the intriguing possibility that such correlated dynamics might be a universal feature of the MIT regardless of the dimensionality. Contents 0.1 Introduction 1 0.2 Metal-insulator transition in two dimensions 3 0.3 Glassy freezing of electrons in two dimensions 15 0.4 Summary 28 0.5 Discussion 29 0.6 Acknowledgments 33 References 34 Free energy landscape Configuration space coordinate F Glass Fig. 0.1 The free-energy (F ) landscape of a glassy system. The horizontal axis represents the one-dimensional projection of the configurational coordinates of the degrees of freedom.Metal-insulator transition in two dimensions ¿ Lee and Ramakrishnan 1985). They have an additional advantage that all the relevant parameters, carrier concentration, disorder and interactions, can be varied relatively easily. This review will describe some of the work that has demonstrated that the 2DES in Si is an excellent model system not only for studying the MIT in two dimensions (2D), but also for investigating the nearly universal nonequilibrium behavior exhibited by a large class of both three-dimensional (3D) and 2D systems (e.g. spin glasses, supercooled liquids, granular films). In fact, the work on the 2DES in Si provides additional strong evidence that many such universal features are robust manifestations of glassiness, regardless of the dimensionality of the system. The dimensionality plays an important role in the MIT. In 2D, for example, the very existence of the metal and the MIT had been questioned for many years. Recently, considerable experimental evidence has become available in favor of such a transition. Some of that work has been described in several review papers (e.g. Kravchenko and Sarachik 2004) with a focus on very clean (low-disordered) samples. This review will first extend that discussion to the cases of higher disorder in order to (a) demonstrate that the 2D MIT is observed in all 2DES in Si regardless of the amount of disorder, (b) point out important similarities to the MIT in 3D systems, and (c) set the stage for the discussion of glassy dynamics near the MIT. As summarized below, the 2DES in Si exhibits all the main manifestations of glassiness: slow, correlated dynamics; nonexponential relaxations; diverging equilibration time, as T → 0; aging and memory. The results provide strong support to theoretical proposals describing the 2D MIT as the melting of a Coulomb glass (Dobrosavljević et al.

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Metal-insulator transition of isotopically enriched neutron-transmutation-doped70Ge:Gain magnetic fields

Cited by 12 publications

References 27 publications

Chapter 5. Metal-Insulator Transition in Correlated Two-Dimensional Systems with Disorder

Chapter 5. Metal-Insulator Transition in Correlated Two-Dimensional Systems with Disorder

Metal-Insulator Transition in Homogeneously Doped Germanium

Glassy Dynamics of Electrons Near the Metal–Insulator Transition

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