Photo-excitation of single crystals of La2CuO4+δ near the metal-insulator transition

G. Yu, C. H. Lee, A. J. Heeger, S. W. Cheong, Z. Fisk

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Transient photoconductivity (σph) experiments have been carried out in single crystals of insulating La2CuO4+δ near the metal-insulator transition (δ≈ 1-2%). The time evolution of the σph changes dramatically with light intensity (IL). At low IL, σph is characterized by power law time decay, t, in the nanosecond time regime, and the exponent, α, decreases significantly with increasing IL. As IL increases to 5 × 1015 photons/cm2, σph reaches ∼ 15 S/cm, and the lifetime of the conducting state is enhanced by more than two orders of magnitude: σph exhibits a delayed peak centered at approximately 30 ns. followed by exponential decay with time constant of ∼ 360 ns. The data reveal a continuous distribution of localized electronic states above the (hole) mobility edge; the M-I transition is achieved when the Fermi level is shifted away from the localized states and across the mobility edge either by chemical dopiing or by photo-excitation. The time of σph at high IL implies the formation of metastable metallic droplets after photo-excitation.

Original languageEnglish (US)
Pages (from-to)563-568
Number of pages6
JournalPhysica C: Superconductivity and its Applications
Volume190
Issue number4
DOIs
StatePublished - Jan 15 1992
Externally publishedYes

Fingerprint

photoexcitation
photoconductivity
insulators
single crystals
metals
hole mobility
decay
luminous intensity
time constant
exponents
conduction
life (durability)
photons
electronics

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Energy Engineering and Power Technology
  • Electrical and Electronic Engineering

Cite this

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title = "Photo-excitation of single crystals of La2CuO4+δ near the metal-insulator transition",
abstract = "Transient photoconductivity (σph) experiments have been carried out in single crystals of insulating La2CuO4+δ near the metal-insulator transition (δ≈ 1-2{\%}). The time evolution of the σph changes dramatically with light intensity (IL). At low IL, σph is characterized by power law time decay, t-α, in the nanosecond time regime, and the exponent, α, decreases significantly with increasing IL. As IL increases to 5 × 1015 photons/cm2, σph reaches ∼ 15 S/cm, and the lifetime of the conducting state is enhanced by more than two orders of magnitude: σph exhibits a delayed peak centered at approximately 30 ns. followed by exponential decay with time constant of ∼ 360 ns. The data reveal a continuous distribution of localized electronic states above the (hole) mobility edge; the M-I transition is achieved when the Fermi level is shifted away from the localized states and across the mobility edge either by chemical dopiing or by photo-excitation. The time of σph at high IL implies the formation of metastable metallic droplets after photo-excitation.",
author = "G. Yu and Lee, {C. H.} and Heeger, {A. J.} and Cheong, {S. W.} and Z. Fisk",
year = "1992",
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Photo-excitation of single crystals of La2CuO4+δ near the metal-insulator transition. / Yu, G.; Lee, C. H.; Heeger, A. J.; Cheong, S. W.; Fisk, Z.

In: Physica C: Superconductivity and its Applications, Vol. 190, No. 4, 15.01.1992, p. 563-568.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Photo-excitation of single crystals of La2CuO4+δ near the metal-insulator transition

AU - Yu, G.

AU - Lee, C. H.

AU - Heeger, A. J.

AU - Cheong, S. W.

AU - Fisk, Z.

PY - 1992/1/15

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N2 - Transient photoconductivity (σph) experiments have been carried out in single crystals of insulating La2CuO4+δ near the metal-insulator transition (δ≈ 1-2%). The time evolution of the σph changes dramatically with light intensity (IL). At low IL, σph is characterized by power law time decay, t-α, in the nanosecond time regime, and the exponent, α, decreases significantly with increasing IL. As IL increases to 5 × 1015 photons/cm2, σph reaches ∼ 15 S/cm, and the lifetime of the conducting state is enhanced by more than two orders of magnitude: σph exhibits a delayed peak centered at approximately 30 ns. followed by exponential decay with time constant of ∼ 360 ns. The data reveal a continuous distribution of localized electronic states above the (hole) mobility edge; the M-I transition is achieved when the Fermi level is shifted away from the localized states and across the mobility edge either by chemical dopiing or by photo-excitation. The time of σph at high IL implies the formation of metastable metallic droplets after photo-excitation.

AB - Transient photoconductivity (σph) experiments have been carried out in single crystals of insulating La2CuO4+δ near the metal-insulator transition (δ≈ 1-2%). The time evolution of the σph changes dramatically with light intensity (IL). At low IL, σph is characterized by power law time decay, t-α, in the nanosecond time regime, and the exponent, α, decreases significantly with increasing IL. As IL increases to 5 × 1015 photons/cm2, σph reaches ∼ 15 S/cm, and the lifetime of the conducting state is enhanced by more than two orders of magnitude: σph exhibits a delayed peak centered at approximately 30 ns. followed by exponential decay with time constant of ∼ 360 ns. The data reveal a continuous distribution of localized electronic states above the (hole) mobility edge; the M-I transition is achieved when the Fermi level is shifted away from the localized states and across the mobility edge either by chemical dopiing or by photo-excitation. The time of σph at high IL implies the formation of metastable metallic droplets after photo-excitation.

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