Logarithmic Divergence of the Electrical Resistivity in the Metal Hydride<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi>YH</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>−</mml:mo><mml:mi mathvariant="italic">δ</mml:mi></mml:mrow></mml:msub></mml:mrow></mml:math>

Huiberts, J. N.; Griessen, R.; Wijngaarden, Rinke J.; Kremers, M.; Haesendonck, van Ch.

doi:10.1103/physrevlett.79.3724

Cited by 55 publications

(41 citation statements)

References 22 publications

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“…Relaxation of s and n remains absent as long as T , T h1 ͑x͒, but they are restored to their initial values once T exceeds T h2 ͑x͒. The threshold temperatures T h1 ͑x͒ and T h2 ͑x͒ are much higher than T p ͑x͒ and coincide with the temperatures between which hysteresis in s͑T ͒ is observed due to hydrogen vacancy ordering [15], typically of order 200 and 270 K, respectively. Therefore, we keep T below 50 K after illumination.…”

Section: -9007͞01͞86(23)͞5349(4)$1500mentioning

confidence: 92%

Light-Induced Metal-Insulator Transition in a Switchable Mirror

et al. 2001

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Rare earth hydride films can be converted reversibly from metallic mirrors to insulating windows simply by changing the surrounding hydrogen gas pressure at room temperature. At low temperatures, in situ doping is not possible in this way as hydrogen cannot diffuse. However, our finding of persistent photoconductivity under ultraviolet illumination offers an attractive possibility to tune yttrium hydride through the T 0 metal-insulator transition. Conductivity and Hall measurements are used to determine critical exponents. The unusually large value for the product of the static and dynamical critical exponents appears to signify the important role played by electron-electron interactions. DOI: 10.1103/PhysRevLett.86.5349 PACS numbers: 71.30.+h, 71.27. +a, 72.15.-v, 73.50. -h Trivalent rare earth hydrides stabilized in thin film form demonstrate spectacular optical and electronic properties [1][2][3][4][5][6][7][8]. Dihydrides such as YH 2 and LaH 2 are good metals; the trihydrides are large gap semiconductors. A thin film of YH x or LaH x can be transformed rapidly from metal to insulator, from shiny mirror to transparent window, simply by changing the surrounding hydrogen gas pressure or an electrolytic cell potential.The continuous and reversible nature of the transformation, as well as the fine-tuning of materials properties afforded by the periodic table, provide a compelling basis for technological development. These same characteristics make switchable mirrors also attractive for scientific scrutiny. The fundamental nature of the metal-insulator transition with hydrogen concentration x is not well understood, although it underlies the attention-getting optical and electronic changes. Pronounced electron-electron interactions have been posited to lead to the opening of the large optical gap [9,10]. If experimentally confirmed as the causative agent [11,12], metal hydride films would be placed in the broad class of highly correlated materials that include transition metal oxides, cuprate superconductors, and colossal magnetoresistance perovskites. Unlike nearly all Mott-Hubbard systems, however, the metalinsulator transition in YH x and LaH x is continuous, unaccompanied by a structural phase transition, and could provide a rare window on critical behavior in the strong electron interactions limit.We systematically investigate the magnetotransport properties of YH x for temperatures T between 0.35 and 293 K in magnetic fields H up to 14 T for chosen values of x. Metal-insulator transitions are properly defined only at T 0, where the electrical conductivity is finite in the metal and zero in the insulator. Hydrogen diffusion is ineffective as a means to drive the transition at low T , but we find that charge carriers created by UV irradiation at T , 1 K persist for days at temperatures as high as 200 K. This persistent photoconductivity enables us to finely tune the conductivity s and the Hall coefficient R H through the quantum critical point. The metal-insulator transition takes place in the hcp g phase...

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Section: -9007͞01͞86(23)͞5349(4)$1500mentioning

confidence: 92%

Light-Induced Metal-Insulator Transition in a Switchable Mirror

et al. 2001

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“…Second, Ca 1Ϫx Y x F 2ϩxϪy H y is a negative H ion conductor, 17 providing an alternative for gas phase 1 and wet electrochemical 4,5 loading. Moreover, these samples are ideally suited to investigate the anisotropic electrical conductivity, 18 since the electrical resistivity at room temperature is as low as that of yttrium single crystals. Finally, the presence of a network of slip planes may also lead to interesting effects in the in-plane diffusion of hydrogen.…”

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Epitaxial switchable yttrium-hydride mirrors

Nagengast

Kerssemakers

Gogh

et al. 1999

Applied Physics Letters

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By means of x-ray scattering and scanning probe microscopy it is shown that high-quality epitaxial Y films can be deposited on (111)-CaF2 substrates. The films can reversibly be switched from metallic YH2 to transparent insulating YH3−δ. Although hydrogen absorption involves an expansion of the lattice and a symmetry change from hcp to fcc, the epitaxiality of the film remains intact during the switching process. The transparency and the insulating nature of the substrate opens unique possibilities to investigate electrically and optically these switchable mirror films in the single crystalline state.

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“…They finally obtained an electronic band structure with only one electron band and one hole band crossing the Fermi energy E F near the center of the Brillouin zone. [11]. The predicted semimetallic character is also not consistent with the existence of an optical gap of 2.8 eV [4].…”

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confidence: 78%

Isotope Effects in Switchable Metal-Hydride Mirrors

1999

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Measurements of optical reflectance, transmittance, and electrical resistivity on the switchable mirror systems YH x and YD x show that the absorption of hydrogen induces the same variations as that of deuterium. In both cases there is a weak transparency window for the metallic dihydride (dideuteride) phase and a yellowish transparency in the insulating trihydride (trideuteride) phase. The slightly higher electrical resistivity of the deuterides is related to the lower energy of their optical phonons. The absence of significant isotope effects in the optical properties of YH x ͑ YD x ͒ is at variance with Peierlslike theoretical models. It is, however, compatible with strong electron correlation models. PACS numbers: 71.30. + h, Spectacular changes in the optical and electrical properties were recently discovered [1,2] in metal-hydride films of yttrium and lanthanum near their metal-insulator transition: the dihydrides are excellent metals and shiny while the trihydrides are insulators and transparent in the visible part of the optical spectrum. The metal-insulator (MI) transition from a shiny to a transparent state is reversible and simply induced at room temperature by changing the surrounding hydrogen gas pressure or electrolytic cell potential [3-5]. All trivalent rare-earth hydrides and even some of their alloys exhibit switchable optical and electrical properties [4,6]. In the transparent state they have characteristic colors: for example, YH 3 is yellowish, LaH 3 red, while some alloys are colorless. These films can therefore be used as switchable mirrors.Soon after their discovery it was realized that the insulating state of the switchable mirrors could probably not be understood in terms of existing one-electron theories, since Wang and Chou [7,8] and Dekker et al. [9] had concluded a few years earlier from self-consistent band structure calculations, that YH 3 was a semimetal with, in fact, a very large band overlap (1.5 eV). By minimizing the total energy, these authors found that the HoD 3 -(P3c1)-type structure was energetically more favorable than the cubic BiF 3 -type structure originally assumed by Switendick [10]. By allowing for Peierls-like displacements of the hydrogen atoms near the metal planes, Wang and Chou [8] found that the total energy could be further lowered by an extra 30 meV per YH 3 . They finally obtained an electronic band structure with only one electron band and one hole band crossing the Fermi energy E F near the center of the Brillouin zone. These difficulties stimulated theorists to reconsider the YH x and LaH x systems. Somewhat similarly to the situation for high-T c superconductors, two clearly different lines of thought have been proposed so far: Peierls-like band structure models and strongly correlated electron models.(i) Strong electron correlation: Already in 1995 Sawatzky [12] suggested that electron correlation effects might explain the existence of the large optical gap in YH 3 . Along the same lines Ng et al. [13,14] discuss the MI transition in LaH x starting ...

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Logarithmic Divergence of the Electrical Resistivity in the Metal HydrideYH3−δ

Cited by 55 publications

References 22 publications

Light-Induced Metal-Insulator Transition in a Switchable Mirror

Light-Induced Metal-Insulator Transition in a Switchable Mirror

Epitaxial switchable yttrium-hydride mirrors

Isotope Effects in Switchable Metal-Hydride Mirrors

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