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Tuesday, September 30, 2025
How will a government shutdown affect NASA? | Rubin Observatory gets an algorithm update
Seminars Digest, Vol 77, Issue 8
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1. Friday 03.10.2025 (info+seminars@itp.ac.ru)
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Message: 1
Date: Tue, 30 Sep 2025 07:02:02 +0000
From: info+seminars@itp.ac.ru
To: staff@itp.ac.ru, students@itp.ac.ru, seminars@itp.ac.ru
Subject: [Landau ITP Seminars] Friday 03.10.2025
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Уважаемые коллеги!
На заседании Ученого совета ИТФ в пятницу 03.10 будет заслушан 1 доклад:
11:30 M. A. Skvortsov, A. V. Polkin
Thermal phase slips in superconducting films and Boussinesq equation
A dissipationless supercurrent state in superconductors can be destroyed by thermal fluctuations. Thermally activated phase slips provide a finite resistance of the sample and are responsible for dark counts in superconducting single photon detectors. The activation barrier for a phase slip is determined by a space-dependent saddle-point (instanton) configuration of the order parameter. In the one-dimensional wire geometry, such a saddle point has been analytically obtained by Langer and Ambegaokar in the vicinity of the critical temperature, $T_c$, and for arbitrary bias currents below the critical current $I_c$. In the two-dimensional geometry of a superconducting strip, which is relevant for photon detection, the situation is much more complicated. Depending on the ratio $I/I_c$, several types of saddle-point configurations have been proposed, with their energies being obtained numerically. We demonstrate that the saddle-point configuration for an infinite superconducting film at $I\to I_c$ is described by the exactly integrable Boussinesq equation solved by Hirota's method. The instanton size is $L_x\sim\xi(1-I/I_c)^{-1/4}$ along the current and $L_y\sim\xi(1-I/I_c)^{-1/2}$ perpendicular to the current, where $\xi$ is the Ginzburg-Landau coherence length. The activation energy for thermal phase slips scales as $\Delta F^\text{2D}\propto (1-I/I_c)^{3/4}$. For sufficiently wide strips of width $w\gg L_y$, a half-instanton is formed near the boundary, with the activation energy being 1/2 of $\Delta F^\text{2D}$.
ID и пароль онлайн-трансляций в Zoom те же, что и для предыдущих трансляций семинаров и докладов на Ученом совете:
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End of Seminars Digest, Vol 77, Issue 8
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