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Critical transport properties of random metals in large magnetic fields.

Proceedings of the National Academy of Sciences of the United States of America · 1997 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 4099

In the critical region near a metal-insulator transition, the threshold behavior of transport properties in random metals is strongly affected by the measuring electromagnetic fields. The abstract attributes phase-coherent effects and a sign reversal of T→0 m…

Study snapshot

PublicationProceedings of the National Academy of Sciences of the United States of America · 1997
Study typeother
Reported directionUnclear
Evidence ratingInsufficient

Abstract

The threshold behavior of the transport properties of a random metal in the critical region near a metal-insulator transition is strongly affected by the measuring electromagnetic fields. In spite of the randomness, the electrical conductivity exhibits striking phase-coherent effects due to broken symmetry, which greatly sharpen the transition compared with the predictions of effective medium theories, as previously explained for electrical conductivities. Here broken symmetry explains the sign reversal of the T --> 0 magnetoconductance of the metal-insulator transition in Si(B,P), also previously not understood by effective medium theories. Finally, the symmetry-breaking features of quantum percolation theory explain the unexpectedly very small electrical conductivity temperature exponent alpha = 0.22(2) recently observed in Ni(S,Se)2 alloys at the antiferromagnetic metal-insulator transition below T = 0.8 K.

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AI evidence extraction

Structured fields below were generated from the paper’s abstract and metadata to make the evidence easier to inspect. Automated extraction may be incomplete or incorrect; verify important details against the original paper.

Study typeother
Effect directionunclear
PopulationNot supplied
Sample sizeNot supplied
ExposureNot supplied
Evidence strengthInsufficientConfidence: 66% · Peer reviewed: yes

Main findings

In the critical region near a metal-insulator transition, the threshold behavior of transport properties in random metals is strongly affected by the measuring electromagnetic fields. The abstract attributes phase-coherent effects and a sign reversal of T→0 magnetoconductance in Si(B,P) to broken symmetry, and states that symmetry-breaking features of quantum percolation theory explain a small conductivity temperature exponent (alpha = 0.22(2)) observed in Ni(S,Se)2 alloys below 0.8 K.

Outcomes measured

  • electrical conductivity
  • magnetoconductance
  • metal-insulator transition behavior
  • electrical conductivity temperature exponent (alpha)

Limitations

  • No quantitative description of the measuring electromagnetic fields (e.g., frequency, intensity) is provided in the abstract.
  • No study design details (experimental setup, sample sizes, or methods) are described in the abstract.
  • Focus is on condensed-matter transport theory/interpretation rather than biological or health outcomes.
View raw extracted JSON
{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": null
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "electrical conductivity",
    "magnetoconductance",
    "metal-insulator transition behavior",
    "electrical conductivity temperature exponent (alpha)"
  ],
  "main_findings": "In the critical region near a metal-insulator transition, the threshold behavior of transport properties in random metals is strongly affected by the measuring electromagnetic fields. The abstract attributes phase-coherent effects and a sign reversal of T→0 magnetoconductance in Si(B,P) to broken symmetry, and states that symmetry-breaking features of quantum percolation theory explain a small conductivity temperature exponent (alpha = 0.22(2)) observed in Ni(S,Se)2 alloys below 0.8 K.",
  "effect_direction": "unclear",
  "limitations": [
    "No quantitative description of the measuring electromagnetic fields (e.g., frequency, intensity) is provided in the abstract.",
    "No study design details (experimental setup, sample sizes, or methods) are described in the abstract.",
    "Focus is on condensed-matter transport theory/interpretation rather than biological or health outcomes."
  ],
  "evidence_strength": "insufficient",
  "confidence": 0.66,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "random metals",
    "transport properties",
    "metal-insulator transition",
    "electromagnetic fields (measuring fields)",
    "electrical conductivity",
    "magnetoconductance",
    "broken symmetry",
    "quantum percolation",
    "Si(B,P)",
    "Ni(S,Se)2",
    "antiferromagnetic transition"
  ],
  "suggested_hubs": []
}
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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1073/pnas.94.20.10532
PubMed: 11038580

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