Temperature dependence of the far-infrared reflectance spectra of Si:P near the metal-insulator transition

Gaymann, A.; Geserich, H. P.; Löhneysen, H. v.

doi:10.1103/physrevb.52.16486

Cited by 48 publications

(32 citation statements)

References 16 publications

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“…However, the conductivity of the x=3.8×10 −5 Be-doped sample is frozen out at low-temperatures, analogous to the insulating Ga 1−x Mn x As samples. Also similar to Ga 1−x Mn x As, both x=3.8×10 −5 and x=9.5×10 near the IMT [21,22].…”

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confidence: 61%

Infrared probe of the insulator-to-metal transition inGa1−xMnxAsandGa<

et al. 2011

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We report infrared studies of the insulator-to-metal transition (IMT) in GaAs doped with either magnetic (Mn) or non-magnetic acceptors (Be). We observe a resonance with a natural assignment to impurity states in the insulating regime of Ga1−xMnxAs, which persists across the IMT to the highest doping (16%). Beyond the IMT boundary, behavior combining insulating and metallic trends also persists to the highest Mn doping. Be doped samples however, display conventional metallicity just above the critical IMT concentration, with features indicative of transport within the host valence band.The insulator-to-metal transition (IMT) becomes exceptionally complex when magnetism is involved, as proven in materials such as mixed-valence manganites, rare-earth chalcogenides, and Mn-doped III-V compounds [1,2]. In all these systems, the electronic and magnetic properties are typically interconnected, creating an entising challenge to understand how magnetism affects the IMT physics. A promising route to isolate differences attributable to the presence of magnetism on the IMT physics is to investigate either magnetic or non-magnetic dopants in the same host. p-doped GaAs is well suited for the task since metallicity in this material can be initiated by non-magnetic (Zn, Be, C) and magnetic (Mn) acceptors. Infrared (IR) experiments reported here for Ga 1−x Be x As and Ga 1−x Mn x As monitor the charge dynamics and electronic structure in the course of the IMT. Our results establish that the onset arXiv:1109.0310v1 [cond-mat.mtrl-sci] 1 Sep 2011

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confidence: 61%

Infrared probe of the insulator-to-metal transition inGa1−xMnxAsandGa<

et al. 2011

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“…3, provides a strong clue that the free-carrier dynamics in these materials is governed by a common mechanism. In doped semiconductors all carriers are delocalized, n = n doped ∼ 10 23 -10 25 m −3 [17][18][19]. In this three-dimensional, marginally metallic state the low ω p 's arise from the low band-filling.…”

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confidence: 99%

“…The decrease of τ upon doping semiconductors has been suggested to result from impurity scattering. [19] However, for conducting polymers impurity or grain boundary scattering is not dominant at room temperature, since this would lower τ in the more disordered systems (lower ω p ). In a non-degenerate electron gas, due to screening, the electron-electron (e-e) scattering cross section Σ ∝ n −1 , and τ e−e ∝ 1/(vnΣ) is independent of n. Apparently, at room temperature electron-phonon (e-ph) scattering dominates.…”

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confidence: 99%

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Metallic state in disordered quasi-one-dimensional conductors

et al. 2001

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The unusual metallic state in conjugated polymers and single-walled carbon nanotubes is studied by dielectric spectroscopy (8-600 GHz). We have found an intriguing correlation between scattering time and plasma frequency. This relation excludes percolation models of the metallic state. Instead, the carrier dynamics can be understood in terms of the low density of delocalized states around the Fermi level, which arises from the competion between disorder-induced localization and interchaininteractions-induced delocalization.The finite conductivity of a metal at zero Kelvin is a consequence of the lattice-periodicity and the finite density of states at the Fermi level (E F ). By breaking translational symmetry, disorder localizes chargecarriers. Upon growing disorder, eventually a metalinsulator transition (MIT) occurs [1], the effect being the stronger the lower the dimensionality. In one dimension (1D) any disorder localizes the electronic states. The MIT in quasi-1D conducting polymers and single-walled carbon nanotubes is also disorder-driven, but its exact nature is under severe debate. Many authors claim the presence of a "heterogeneous" state in which the relevant disorder length-scale is large compared to the electronic correlation-length. In this case, the MIT corresponds to a percolation transition of metallic islands embedded in an amorphous matrix. [2][3][4] Other studies suggest that the MIT is of the Anderson type [1] with disorder occurring on length-scales equal or less than the electronic correlation-length. [5,6] Then, extended and localized states are separated in energy by the mobility edge (E c ), and the MIT occurs when E F crosses E c .

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“…This can be seen for crystalline semiconductors, in particular doped silicon [3][4][5], the best studied case of a system exhibiting an electronically driven MIT. It is now well established that both disorder and correlations play an important role in these systems.…”

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Role of vacancies in metal–insulator transitions of crystalline phase-change materials

et al. 2012

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The study of metal-insulator transitions in crystalline solids is a subject of paramount importance, both from the fundamental point of view and for its relevance to the transport properties of materials. Recently, a metal-insulator transition governed by disorder was observed in crystalline phase-change materials. Here we report on calculations employing Density Functional Theory, which identify the microscopic mechanism that localizes the wave functions and is driving this transition. We show that, in the insulating phase, the electronic states responsible for charge transport are localized inside regions having large vacancy concentrations. The transition to the metallic state is driven by the dissolution of these vacancy clusters and the formation of ordered vacancy layers. These results provide important insights on controlling the wave function localization, which should help to develop conceptually new devices based on multiple resistance states.

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Temperature dependence of the far-infrared reflectance spectra of Si:P near the metal-insulator transition

Cited by 48 publications

References 16 publications

Infrared probe of the insulator-to-metal transition inGa1−xMnxAsandGa<

Infrared probe of the insulator-to-metal transition inGa1−xMnxAsandGa<

Metallic state in disordered quasi-one-dimensional conductors

Role of vacancies in metal–insulator transitions of crystalline phase-change materials

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