Dresden 2020 – scientific programme

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KFM: Fachverband Kristalline Festkörper und deren Mikrostruktur

KFM 3: Dielectric, Elastic and Electromechanical Properties

KFM 3.3: Talk

Monday, March 16, 2020, 12:40–13:00, HSZ 105

Dilute metallicity 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 shows comparatively high values of the dielectric constant ε ′ of ≈ 300 already at room temperature. When cooling the material, these values rise steeply, indicating the vicinity of a ferroelectric phase transition. In SrTiO₃, this transition is suppressed by quantum fluctuations, making the compound a quantum paraelectric with saturation values in ε ′ of the order of 10⁴ [1].

While the parent compound is a wide-gap insulator, reduction of the oxygen content introduces free charge carriers in SrTiO_3−δ. The result is a conducting and even superconducting material with unusually low charge carrier concentrations, made possible by the large effective Bohr radius caused by the high permittivity of the lattice [2].

While DC-data is available [3], we investigate the conductivity of SrTiO_3−δ depending on frequency and temperature using broadband dielectric spectroscopy. The Drude model is applied to this AC-data to retrieve scattering rate, mobility and effective mass of the charge carriers.

[1] R. Viana et al., Phys. Rev. B 50, 601 (1994)
[2] X. Lin et al., Phys. Rev. X 3, 021002 (2013)
[3] C. Collignon et al., Ann. Rev. Cond. Mat. Phys. 10, 25-44 (2018)