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Today's Topics:
1. Thursday 27.10.2025 - ITP/CAS Colloquium (Stanislav Apostolov)
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Message: 1
Date: Thu, 27 Nov 2025 09:01:06 +0300
From: Stanislav Apostolov <sapostolov@itp.ac.ru>
To: staff@itp.ac.ru, students@itp.ac.ru, seminars@itp.ac.ru
Subject: [Landau ITP Seminars] Thursday 27.10.2025 - ITP/CAS
Colloquium
Message-ID: <a7302eec08306ec1f0385e9ad435fed3@itp.ac.ru>
Content-Type: text/plain; charset="utf-8"; Format="flowed"
Уважаемые коллеги!
На онлайн коллоквиум по теоретической физике в четверг 27.11 будут
заслушаны 2 доклада:
1) Ordered and Tunable Majorana-Zero-Mode Lattice in Iron-Based
Superconductors
в 10:00
Hong-Jun Gao (Institute of Physics, Chinese Academy of Sciences)
Majorana zero-modes (MZMs) are spatially-localized zero-energy
fractional quasiparticles with non-Abelian braiding statistics. They are
believed to hold great promise for topological quantum computation. By
using low-temperature and strong-magnetic-field scanning tunneling
microscopy/spectroscopy, a breakthrough of Majorana zero mode has been
firstly achieved in a single material platform of high-Tc iron-based
superconductor, FeTe0.55Se0.45. The mechanism of two distinct classes of
vortices presented in this system was revealed, which directly tied with
the presence or absence of zero-bias peak. We further found the Majorana
conductance plateau in vortices. Both the extrinsic instrumental
convoluted broadening and the intrinsic quasiparticle poisoning can
reduce the conductance plateau value, and when extrinsic instrumental
broadening is removed by deconvolution, the plateau nearly reaches a
2e2/h quantized value. Moreover, we confirmed the existence of MZMs in
the vortex cores of CaK-Fe4As4 and LiFeAs. Based on these works
mentioned above, most recently, we have successfully achieved the
large-scale, highly-ordered and tunable MZM lattice in strained LiFeAs.
Notably, more than 90% of the vortices are topological and possess the
characteristics of isolated MZMs at the vortex center, forming ordered
MZM lattice with the density and the geometry tunable by external
magnetic field. With decreasing the spacing of neighboring vortices, the
MZMs start to couple with each other. This kind of materials combine the
advantages of a simple material, high- Tc, large ratio of Δ/EF and etc.
Our results show a great potential of MZMs in the application of
topological quantum computation in the future.
Biography
Prof. Hong-Jun Gao obtained his Ph.D. from Peking University in 1994. He
is now a Group Leader in Institute of Physics, an Academician of the
CAS, and an Academician of the Developing-country Academy of Sciences
(TWAS). From 1997 to 2000, he worked at the Oak Ridge National
Laboratory (ORNL) as a Guest Scientist. He was the Scientific Secretary
of the International Union of Vacuum Science, Technology, and
Applications (IUVSTA) in the triennium 2004-2007, and the Chairman of
the NSTD, IUVSTA (2010-2013). He served as an Associate Editor for Appl.
Phys. Lett. From 2010 to 2018, and are editorial board members for
several international journals. He was the Vice-President of the U-CAS
and Chair of the U-CAS Advisory Committee of Sciences from 2014 to 2015.
In the past years he visited several universities in the US as a
Visiting Professor or Scientific Consultant.
His research interests focus on construction and physical properties of
quantum nanostructures and scanning tunneling microscopy/spectroscopy
(STM/STS). He has 8 international books/chapters, more than 500 journal
publications including Science, Nature, Nature series, Phys. Rev. Lett.,
J. of Amer. Chem. Soc., Adv. Mater., and more than 120 invited talks.
The total citation is more than 35000 and the H-index=95. His research
works have been highlighted by the American Physical Society-physics,
Physical Review Focus, Science News, Nature Materials, and Nature
Nanotechnology, etc.
He was awarded several international Awards, including the "Humboldt
Research Award" in 2010, the "OCPA AAA (Robert Prize)" in 2008 (OCPA:
Overseas Chinese Physics Association; AAA: Achievement in Asia Award),
and the "TWAS Prize in Physics 2009" (TWAS: Developing-country (Third
World) Academy of Sciences). He also got a few top-level awards in
China, for example, "Tan Kah Kee Science Awards on Mathematics and
Physics 2018", "Science and Technology Awards of the Ho Leung Ho Lee
2012", and "Outstanding Science and Technology Achievement Prize of the
Chinese Academy of Sciences 2013".
2) Balancing an Inverted Pendulum Under Random Force: Statistics of the
Never-Falling Trajectory
в 11:00
Mikhail A. Skvortsov (L.D. Landau Institute for Theoretical Physics,
Russian Academy of Sciences)
Various fields of physics involve a class of problems related to
minimization of a functional of an angular variable, which depends on a
single coordinate, in the presence of a random force. The corresponding
second-order differential equation of motion is unstable, making its
solution a non-trivial numerical task. A paradigmatic model for this
class of phenomena is finding the never-falling trajectory (NFT) of an
inverted pendulum subjected to a time-dependent horizontal force (the
Whitney problem).
We have shown that the Whitney problem, considered over the entire time
axis, has a unique solution, and for the first time, we have raised the
question of describing its statistical properties when averaged over an
ensemble of random forces. For the white-noise random force, we
construct a complete field-theoretical description of the statistics of
the NFT, based in the the Parisi-Sourlas supersymmetric representation.
The joint probability distribution function of the angle and its
velocity is expressed via the solution of an auxiliary Fokker-Planck
problem and found analytically in the limits of weak and strong noise.
We also determine the Lyapunov exponent, describing the divergence of
nearby solutions around the NFT.
Biography
Mikhail A. Skvortsov graduated from the Moscow Institute of Physics and
Technology in 1995 and got his PhD in 1998. Since then, he has been
continuously employed at the Landau Institute for Theoretical Physics.
From 2014 to 2021, he served as an Associate Professor at the Skolkovo
Institute of Science and Technology. M. A. Skvortsov is a recognized
specialist in the physics of disordered and superconducting systems. His
key scientific contributions include explaining the giant fluctuation
Nernst effect in superconductors, investigating ergodicity and
localization on random regular graphs, developing the Keldysh action
approach for disordered superconductors, describing the inhomogeneous
state in dirty superconductors, constructing the theory of dynamical
localization in quantum dots under periodic driving, characterizing the
statistics of the never-falling trajectory in the random Whitney
problem.
Zoom: 829 6586 0457, Passcode: 911242
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End of Seminars Digest, Vol 79, Issue 8
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A quick roundtable on whether perfect recall is a dream or a nightmare (Everyone agreed that this would not be good for the future of humanity)
Vote for next month’s pick: poll closes Nov. 30
Bonus recs for fans of stories about memory, identity, and the slippery nature of truth
Plus: fresh sci-fi coverage
