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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 14: Postersession KFM

KFM 14.24: Poster

Mittwoch, 3. April 2019, 16:00–18:30, Poster C

Charge carrier dynamics in SrTiO_3−δ — •Thomas Schunk-Born¹, Christoph Grams¹, Kamran Behnia², and Joachim Hemberger¹ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Laboratoire Physique et Etude de Matériaux (UMR 8213 CNRS-ESPCI), PSL Research University, Paris, France

Pristine SrTiO₃ is a quantum paraelectric insulator with a comparatively high permittivity of ∼300 already at room temperature. Upon cooling, its dielectric constant ε ′ shows a steep rise, usually indicative of a ferroelectric phase transition. In SrTiO₃, this transition is suppressed by quantum fluctuations and instead a saturation value of ε ′ of the order of 10⁴ is observed [1].

By reducing the oxygen content, charge carriers are introduced in SrTiO_3−δ. Due to the large effective Bohr radius caused by the high permittivity, the material becomes conducting and even superconducting at unusually low charge carrier densities [2].

Using broadband dielectric spectroscopy, we investigate the conductivity of samples with different charge carrier densities depending on frequency and temperature to show an evolution from insulating (σ ′ ≈ 0), to variable-range-hopping (σ ′ ∝ ω^s), to Drude-metal (σ ′ ∝ ω ⁻²) behavior.

[1] R. Viana et al., Phys. Rev. B 50, 601 (1994)
[2] X. Lin et al., Phys. Rev. X 3, 021002 (2013)