title: Dynamics of a robust photo-induced insulator-metal transition driven by coherent and broad-band light in epitaxial films of La(0.625-y)Pr(y)Ca(0.375)MnO(3).
abstract: A dramatic drop of ≈5 orders of magnitude in the resistance (R) of La(0.175)Pr(0.45)Ca(0.375)MnO(3) epitaxial films upon exposure to optical photons derived from both continuous and pulsed lasers, as well as broad-band sources at temperatures (T) < 30 K is reported. The strength of change is a sensitive function of both the incident photon flux and temperature. Under isothermal conditions the photo-generated low resistance state persists eternally after removal of light. This non-equilibrium state is metallic, as revealed by the positive dR/dT for T ≤ T(p) (≈120 K). This electrically conducting state is presumably ferromagnetic as T(p) coincides with the temperature where a weak ferromagnetism sets in on cooling the insulating film from room temperature. To rule out the possibility of photon-induced local heating of the sample as a mechanism of the observed effects, photo-illumination experiments were performed under identical conditions on thin films of two non-charge-ordered manganites deposited on substrates of similar thermal conductivity. Our model for the observed transition encompasses a global charge-ordered state in which ferromagnetic metallic clusters of fraction p much less than the critical fraction p(c) for percolation exists at low temperatures. Photo-induced melting of the charge-ordered state increases this fraction beyond p(c) in a cumulative manner as successive pulses of light fall on the sample.
authors.affiliation: Condensed Matter—Low Dimensional Systems Laboratory, Department of Physics, Indian Institute of Technology Kanpur, Kanpur-208016, India.
authors.forename: S
authors.initials: S
authors.lastname: Chaudhuri
authors.forename: N K
authors.initials: NK
authors.lastname: Pandey
authors.forename: Shrikant
authors.initials: S
authors.lastname: Saini
authors.forename: R C
authors.initials: RC
authors.lastname: Budhani
mesh_terms: D002118:Calcium / Q000737:chemistry*; D007811:Lanthanum / Q000737:chemistry*; D008027:Light; D008280:Magnetics; D017895:Manganese Compounds / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D017785:Photons; D010825:Physics / Q000379:methods*; D011221:Praseodymium / Q000737:chemistry*; D013696:Temperature
chemical_list: D017895:Manganese Compounds; D010087:Oxides; C027424:manganese oxide; D007811:Lanthanum; D011221:Praseodymium; D002118:Calcium