Narrow-Gap Semiconductors

Dornhaus, Ralf; Nimtz, G.; Schlicht, B.

doi:10.1007/bfb0044919

Cited by 238 publications

(181 citation statements)

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“…13,14 PbS is a diamagnetic semiconductor with a narrow gap of 0.4 eV. 19 Despite the disadvantage of low Curie temperature that only allows such a device to work at low temperatures, EuS/PbS is an excellent starting system from both technological and fundamental points of view. First of all, EuS and PbS both crystallize in the rocksalt structure and the lattice mismatch is very small, of only 0.5%.…”

Section: Spin-injection Device Based On Eus Magnetic Tunnel Barriersmentioning

confidence: 99%

Spin-injection device based on EuS magnetic tunnel barriers

Filip¹,

LeClair²,

Smits³

et al. 2002

Applied Physics Letters

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We propose a spin-valve device consisting of a nonmagnetic semiconductor quantum well, sandwiched between ferromagnetic semiconductor layers that act as barriers. The total conductance through such a trilayer depends on the relative magnetization of the two ferromagnetic-barrier layers which act as “spin filters.” With respect to practical realization, EuS/PbS heterostructures may be a suitable candidate. The magnetoresistance should exceed 100% for a wide range of the thicknesses of both the quantum well and the ferromagnetic barriers. From a fundamental physics point of view, the device may not only give insight into the spin lifetimes of the nonmagnetic layer, but the strong spin accumulation taking place in the quantum well may lead to novel optical and nuclear magnetic resonance properties.

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Section: Spin-injection Device Based On Eus Magnetic Tunnel Barriersmentioning

confidence: 99%

Spin-injection device based on EuS magnetic tunnel barriers

Filip¹,

LeClair²,

Smits³

et al. 2002

Applied Physics Letters

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“…From the point of view of the electronic structure and the optical properties EuS-PbS multilayers form PbS multiple quantum well ͑or superlattice͒ with the fundamental electronic transitions in the infrared. [34][35][36] Since in this structure EuS is a semiconductor with much larger energy gap, EuS is an electron barrier material. EuS crystals usually show semi-insulating electric properties, whereas PbS is a well-known narrow gap semiconductor with low carrier concentration and semimetallic character of electric conductivity.…”

Section: Introductionmentioning

confidence: 99%

“…EuS crystals usually show semi-insulating electric properties, whereas PbS is a well-known narrow gap semiconductor with low carrier concentration and semimetallic character of electric conductivity. 34 The EuS-PbS multilayers are ferromagnetic nanostructures combining both the simple magnetic system ͑local spin-only magnetic moments in an insulating crystal coupled via short-range exchange interactions͒, a well-known cubic crystal structure, and a good epitaxial compatibility of both ferromagnetic and diamagnetic layers. Therefore, these structures can be considered as the model low-dimensional nonmetallic Heisenberg ferromagnets.…”

Section: Introductionmentioning

confidence: 99%

Ferromagnetic transition in EuS-PbS multilayers

et al. 1999

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Document VersionPublisher's PDF, also known as Version of Record (includes final page, issue and volume numbers)Please check the document version of this publication:• A submitted manuscript is the author's version of the article upon submission and before peer-review. There can be important differences between the submitted version and the official published version of record. People interested in the research are advised to contact the author for the final version of the publication, or visit the DOI to the publisher's website.• The final author version and the galley proof are versions of the publication after peer review.• The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication Citation for published version (APA):Stachow-Wojcik, A., Story, T., Dobrowolski, W., Arciszewska, M., Galazka, R. R., Kreijveld, M. W., ... Sipatov, A. Y. (1999). Ferromagnetic transition in EuS-PbS multilayers. Physical Review B, 60(22), 15220-15229. DOI: 10.1103/PhysRevB.60.15220 General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal ? Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. The magnetic properties of multilayers of ferromagnetic EuS intercalated with diamagnetic PbS were studied as a function of the EuS layer thickness ͑varying from 2 to 200 ML͒. The critical temperature T C of the paramagnet-ferromagnet phase transition was determined from magnetization vs temperature measurements and was found to depend on the underlying substrate ͓KCl ͑100͒ vs BaF 2 ͑111͔͒ as well as on the thickness of the EuS layer. For thick layers (d EuS Ϸ200 ML), which mimic semibulk EuS, the T C values were found shifted with respect to the bulk EuS ͑about 1 K up for layers grown on KCl and about 3 K down for layers grown on BaF 2 ). This effect is attributed to stress resulting mainly from the difference of thermal expansion coefficients between the substrate and the structure. For thin layers (d EuS Ͻ10 ML), a systematic reduction of T C with decreasing EuS layer thickness was observed. This behavior is discussed from two points of view: ͑a͒ the reduction of the average number of magnetic neighbors because of the increasing role of the interface for the thin layers, and ͑b͒ the three-dimensional/two-dimensional ͑3D/2D͒ crossover from a 3D Heisenberg-type ferromagnet to a 2D XY or Ising-like sy...

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“…It has a rocksalt structure and has been treated with reasonable success using ionic models (i.e., Pb 2+ Te 2− ) [12]. The material can be doped to degeneracy by either vacancies or thirdelement dopants, with typical carrier concentrations in the range of 10 18 − 10 20 cm −3 [13,14,15]. In comparison with similar semiconducting materials such as SnTe, GeTe, and InTe, it was previously anticipated that doped PbTe would only superconduct below approximately 0.01 K, if at all [16].…”

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confidence: 99%

Evidence for Charge Kondo Effect in Superconducting Tl-Doped PbTe

et al. 2005

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We report results of low-temperature thermodynamic and transport measurements of Pb1−xTlxTe single crystals for Tl concentrations up to the solubility limit of approximately x = 1.5%. For all doped samples, we observe a low-temperature resistivity upturn that scales in magnitude with the Tl concentration. The temperature and field dependence of this upturn are consistent with a charge Kondo effect involving degenerate Tl valence states differing by two electrons, with a characteristic Kondo temperature TK ∼ 6 K. The observation of such an effect supports an electronic pairing mechanism for superconductivity in this material and may account for the anomalously high Tc values. The Kondo effect arises from the interaction of conduction electrons with degenerate degrees of freedom in a material and is usually associated with dilute magnetic impurities in a nonmagnetic host. In such cases, the two degenerate states correspond to the impurity spins oriented up or down. Second order scattering processes involving virtual intermediate states lead to the well-known logarithmic increase in resistivity at low temperatures, which saturates in the unitary scattering limit below a characteristic Kondo temperature [1]. However, other systems comprising two degenerate degrees of freedom can also lead to Kondo-like phenomena [2]. In particular, a "charge Kondo effect," corresponding to dilute impurities with two degenerate charge states, has been proposed in the negative-U Anderson model [3], though to date there has not been an experimental realization of such an effect. Significantly, the quantum valence fluctuations implicit in such a model, which involve pairs of electrons that tunnel on and off impurity sites, also provide an electronic pairing mechanism for superconductivity [4,5,6,7].Thallium is one of several elements that is known to skip valences, such that only Tl 1+ and Tl 3+ are observed in ionic compounds, corresponding to electron configurations 6s 2 and 6s 0 respectively. Compounds that one would otherwise expect to contain divalent Tl are found to disproportionate. For example, TlBr 2 is more specifically Tl I Tl III Br 4 , and TlS is likewise Tl I Tl III S 2 [8]. This effect is driven by the stability of a filled shell in conjunction with the polarizability of the material. In this case, Tl 2+ can be characterized by a negative effective U , where U n = (E n+1 − E n ) − (E n − E n−1 ) < 0 and n labels the valence state [9,10,11]. For this reason, valence-skipping elements provide experimental access to negative-U behavior and are therefore suitable candidate impurities for realizing a charge Kondo effect in a bulk material.

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Narrow-Gap Semiconductors

Cited by 238 publications

References 0 publications

Spin-injection device based on EuS magnetic tunnel barriers

Spin-injection device based on EuS magnetic tunnel barriers

Ferromagnetic transition in EuS-PbS multilayers

Evidence for Charge Kondo Effect in Superconducting Tl-Doped PbTe

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