# Theoretical seminars in Kapitza Institute for Physical Problems

## Velocity distribution functions and intermittency in one-dimensional randomly forced Burgers turbulence

25 October, tomorrow in 11:30

Viktor Dotsenko (Universite Jussieu, Paris)

The problem of one-dimensional randomly forced Burgers turbulence is considered in terms of (1+1) directed polymers. In the limit of strong turbulence (which corresponds to the zero temperature limit for the directed polymer system) using the replica technique a general explicit expression for the joint distribution function of two velocities separated by a finite distance is derived. In particular, it is shown that at length scales much smaller than the injection length of the Burgers random force the moments of the velocity increment exhibit typical strong intermittency behavior.
Literature:
J.Stat.Mech., 083302 (2018); arXiv:1804.08294.

## Josephson and non-Josephson emission from Bi_{2}Sr_{2}CaCu_{2}O_{8+δ} mesa structures

22 November in 11:30

Vladimir Krasnov (Stockholm University, Sweden)

Mesa structures made of Bi

References:

[1] E. A. Borodianskyi and V.M. Krasnov, Josephson emission with frequency span 1–11 THz from small Bi

[2] S. O. Katterwe, H. Motzkau, A. Rydh, and V. M. Krasnov, Coherent generation of phonon-polaritons in Bi

[3] V.M. Krasnov, S.O. Katterwe, & A. Rydh, Signatures of the electronic nature of pairing in high-Tc superconductors obtained by non-equilibrium boson spectroscopy, Nature Commun. 4, 2970 (2013).

_{2}Sr_{2}CaCu_{2}O_{8+δ}high-temperature superconductor represent stacks of atomic scale intrinsic Josephson junctions. When voltage is applied to such mesas, they can generate various types of waves (photons, phonons, polaritons, magnons, plasmons) in a variety of different ways. In this talk I will overview both Josephson and non-Josephson mechanisms of emission, including the standard ac-Josephson effect for emission of electromagnetic waves [1], segnetoelectric effect for emission of phonons and polaritons [2] and non-equilibrium quasiparticle relaxation and recombination for emission of any type of bosons, having strong electron-boson interaction and participating in pairing [3]. Those effects are important both for applied research, e.g., creation of tunable, compact, continuous wave and monochromatic THz source with a frequency span in the whole THz gap region and beyond 0.1-15 THz [1,2], and for fundamental understanding of the mechanism of pairing in high-temperature superconductors [3].References:

[1] E. A. Borodianskyi and V.M. Krasnov, Josephson emission with frequency span 1–11 THz from small Bi

_{2}Sr_{2}CaCu_{2}O_{8+δ}mesa structures, Nature Commun. 8, 1742 (2017).[2] S. O. Katterwe, H. Motzkau, A. Rydh, and V. M. Krasnov, Coherent generation of phonon-polaritons in Bi

_{2}Sr_{2}CaCu_{2}O_{8+x}intrinsic Josephson junctions, Phys. Rev. B 83, 100510(R) (2011).[3] V.M. Krasnov, S.O. Katterwe, & A. Rydh, Signatures of the electronic nature of pairing in high-Tc superconductors obtained by non-equilibrium boson spectroscopy, Nature Commun. 4, 2970 (2013).

6 December in 11:30

W. Belzig

Seminars are held on Thursdays in the conference hall Kapitza Institute for Physical Problems in Moscow, beginning at 11:30.

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