Department of Complex Matter
Jamova cesta 39, 1000 Ljubljana, Slovenia

Dynamics of Quantum matter

We explore non-equilibrium many-body dynamics in quantum systems that experience symmetry-breaking, topological, or jamming transitions. These systems encompass superconductors, charge-density wave, and magnetic materials.

Experimental Soft Matter Physics

The research is conducted within the “Light and Matter” research program. The interaction of light with matter is one of the most important fields of physics and optical processes are indispensable in many branches of modern industry.

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April 11, 2024
Dr. Dragan Mihailović, a leading researcher in the field of quantum systems at the Jožef Stefan Institute (IJS), has successfully won the third project of the European Research Council (ERC), HIMMS (High-Resolution ...
Home / Events / QT Future Seminar “Theory of superconductivity due to Ngai’s mechanism in li…

QT Future Seminar “Theory of superconductivity due to Ngai’s mechanism in lightly doped SrTiO3”

December 5, 2023 , 11:15 , Seminar room for physics (JSI main building)

Dmitry E. Kiselov

We develop a theory of superconducting pairing in low-density Strontium titanate based upon the idea of quadratic coupling of electron density to soft transverse optical phonons [1]. This coupling leads to static attractive potential between electrons which decays in real space exponentially with the length $l_{eff}$ that scales inversely with soft optical gap $\omega_T$ . For low electron densities $n \leq 10^{18} cm^{-3}$ attraction between electrons can be considered local and superconducting transition temperature $T_c$ is calculated using old results [2]. We use independently obtained magnitude g of the quadratic coupling strength and find $T_c(n)$ dependence in agreement with experimental data [3] for low doping. Next, we show that suppression of $T_c$ by hydrostatic pressure [4] and strong increase of $T_c$ due to isotop substitution $^{16}O \to\,^{18}O$ observed in [5] are qualitatively explained within our theory.

[1] K. L. Ngai, Phys. Rev. Lett. 32, 215 (1974)

[2] L. P. Gor’kov and T. K. Melik-Barkhudarov, Sov. Phys. – JETP 40, 1452 (1961)

[3] X. Lin, et al, Phys. Rev. Lett. 112, 207002 (2014).

[4] C. Enderlein, et al, Nature Comm. (2020)

[5] A. Stucky, et al, Scientific Reports, 6:37582 (2016)