Superconducting and Insulating Phases of Disordered FeSe Thin Films in a Magnetic Field

Schneider, Reinhard; Zaitsev, A. G.; Fuchs, D.; Löhneysen, H. v.

doi:10.1007/s10909-014-1227-0

Cited by 4 publications

(2 citation statements)

References 34 publications

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“…Such situation is realized in a variety of materials, e.g. in such superconducting films as amorphous Bi and Pb [48,49], MoC [50], MoGe [51], Ta [52], InO [53][54][55][56], NbN [57][58][59], TiN [60][61][62][63], and FeSe [64][65][66]. Also, 2D superconductivity was observed in such novel materials as LaAlO 3 /SrTiO 3 [67,68], SrTiO 3 surface [69,70], MoS 2 [71][72][73], LaSrCuO surface [74], and Li x ZrNCl [75][76][77][78].…”

Section: D Interacting Disordered Electron System With Supercondmentioning

confidence: 99%

Finkel’stein Nonlinear Sigma Model: Interplay of Disorder and Interaction in 2D Electron Systems

Burmistrov

2019

J. Exp. Theor. Phys.

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In this paper 1 I briefly review recent theoretical results derived within the Finkel'stein nonlinear sigma model approach for description of two-dimensional interacting disordered electron systems. The examples include an electron system with two valleys, electrons in a double quantum well, electrons on the surface of a topological insulator, an electron system with superconducting correlations, and the integer quantum Hall effect.

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Section: D Interacting Disordered Electron System With Supercondmentioning

confidence: 99%

Finkel’stein Nonlinear Sigma Model: Interplay of Disorder and Interaction in 2D Electron Systems

Burmistrov

2019

J. Exp. Theor. Phys.

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“…In contrast, for thin films (≤50 nm), superconductivity disappeared [16] and insulator-like behavior (i.e., increasing resistivity with decreasing temperature) was observed [17,18]. Although the insulator-like behavior has been proposed to originate from the lattice strain in the films [16] and/or highly textured FeSe surfaces (i.e., the coexistence of nonsuperconducting and granular superconducting phases) [19,20], the physical origin and mechanism of the insulator-like behavior of thin FeSe films are still under debate.…”

Section: Introductionmentioning

confidence: 99%

Insulator-like behavior coexisting with metallic electronic structure in strained FeSe thin films grown by molecular beam epitaxy

et al. 2019

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This paper reports that ~10-nm-thick iron selenide (FeSe) thin films exhibit insulator-like behavior in terms of the temperature dependence of their electrical resistivity even though bulk FeSe has a metallic electronic structure that has been confirmed by photoemission spectroscopy and first-principles calculations. This apparent contradiction is explained by potential barriers formed in the conduction band. Very thin FeSe epitaxial films with various atomic composition ratios ([Fe]/[Se]) were fabricated by molecular beam epitaxy and classified into two groups with respect to lattice strain and electrical properties. Lattice parameter a increased and lattice parameter c decreased with increasing [Fe]/[Se] up to 1.1 and then a levelled off and c began to decrease at higher [Fe]/[Se]. Consequently, the FeSe films had the most strained lattice when [Fe]/[Se] was 1.1, but these films had the best quality with respect to crystallinity and surface flatness. All the FeSe films with [Fe]/[Se] of 0.8-1.9 exhibited insulator-like behavior, but the temperature dependences of their electrical resistivities exhibited different activation energies E a between the Se-rich and Fe-rich regions; i.e., E a were small (a few meV) up to [Fe]/[Se]=1.1 2 but jumped up to ~25 meV at higher [Fe]/[Se]. The film with [Fe]/[Se]=1.1 had the smallest E a of 1.1 meV and exhibited an insulator-superconducting transition at 35 K with zero resistance under gate bias.The large E a of the Fe-rich films was attributed to the unusual lattice strain with tensile in-plane and relaxed out-of-plane strains. The large E a of films with [Fe]/[Se]>1.1 resulted in low mobility with a high potential barrier of ~50 meV in the conduction band for percolation carrier conduction compared with that of the [Fe]/[Se]=1.1 film (~17 meV). Therefore, the Fe-rich films exhibited remarkable insulator-like behavior similar to a semiconductor despite their metallic electronic structure. The high potential barrier of Fe-rich films is tentatively attributed to the presence of large amounts of excess Fe, which could plausibly cause a broad superconducting transition without zero resistance under gating.

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Superconductor-insulator transitions: Phase diagram and magnetoresistance

2015

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The influence of the disorder-induced Anderson localization and electron-electron interaction on the superconductivity in two-dimensional systems is explored. We determine the superconducting transition temperature T c , the temperature dependence of the resistivity, the phase diagram, and the magnetoresistance. The analysis is based on the renormalization group (RG) for a nonlinear sigma model. The derived RG equations are valid to the lowest order in disorder but for an arbitrary electron-electron interaction strength in a particle-hole and the Cooper channels. Systems with preserved and broken spin-rotational symmetry are considered, with both short-range and long-range (Coulomb) interactions. In the case of short-range interaction, we identify parameter regions where the superconductivity is enhanced by localization effects. Our RG analysis indicates that the superconductor-insulator transition is controlled by a fixed point with a resistivity R c of the order of the quantum resistance R q = h/4e 2 . When a transverse magnetic field is applied, we find a strong nonmonotonous magnetoresistance for temperatures below T c .

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Superconducting and Insulating Phases of Disordered FeSe Thin Films in a Magnetic Field

Cited by 4 publications

References 34 publications

Finkel’stein Nonlinear Sigma Model: Interplay of Disorder and Interaction in 2D Electron Systems

Finkel’stein Nonlinear Sigma Model: Interplay of Disorder and Interaction in 2D Electron Systems

Insulator-like behavior coexisting with metallic electronic structure in strained FeSe thin films grown by molecular beam epitaxy

Superconductor-insulator transitions: Phase diagram and magnetoresistance

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