CPQM Research Seminars 2016 – 2017

An overview of the Multi-Configurational Time-Dependent Hartree for Bosons (MCTDHB) theory [1,2] and its applications to study static and highly non-equilibrium dynamics in ultracold bosonic clouds is given.  We first discuss the key physical idea behind the MCTDHB method. Next we connect the MCTDHB method with other many-body and mean-field tools available in the field of ultracold atoms. The most striking feature of the MCTDHB method is its ability to describe condensation and coherence, depletion and multi-fold fragmentation phenomena in static setups and dynamic highly non-equilibrium processes. Here we use the well-known and widely-used definition of condensation given by O. Penrose and L. Onsager [Phys. Rev. 104, 576 (1956)] in terms of eigenvalues of the reduced one-particle density matrix: When only one eigenvalue has a macroscopic occupation the system is condensed, when several – it is fragmented.

We present and discuss several typical dynamical scenarios where the initially condensed systems start to lose the coherence dynamically, and, eventually become fragmented. We propose a protocol based on the matter-wave interferometry for quantitative measurements of the loss of coherence and fragmentation. This interferometric-based protocol to discriminate, probe, and measure the fragmentation is general and can be applied to ultra-cold systems with attractive, repulsive, short- and long-range interactions. We also would like to announce the release of the MCTDHB-Laboratory [3]– a FREE-for-download, cross-platform (Mac-Win-Linux) MCTDHB solver of the many-boson Time-dependent Schrödinger equation with a simple graphical mouse-click JavaFX-based front-end interface.

Abstract:

I will argue that electron transport in high mobility semiconductors at moderately low temperatures may be described using a hydrodynamic approach. The hydrodynamic flow that arises in this case is markedly different from the Stokes flow. The passage of electric current induces temperature gradient that are linear in the current. As a result, the resistivity of the system is determined not only by the viscosity of the system but also by its thermal conductivity.

Reflection spectra of synthetic three-dimensional opaline photonic crystals are studied both experimentally and theoretically. We demonstrate that in presence of GeSbTe (GST) chalcogenide capping layer, the reflection spectra have peaks associated with diffraction Wood’s anomalies. The calculated electromagnetic near-field distributions of incident light demonstrate two types of resonances localized in the sub-interface region. The experimental reflection spectra are in a good agreement with theoretical calculations performed by the Fourier modal method in the scattering matrix form.

Host: Boris Fine

Consider a mobile impurity particle injected in a one-dimensional quantum fluid with some initial velocity, v0. What will be the relaxation dynamics of the impurity? Numerical and seminumerical studies of finite systems (N<50, where N is the number of particles of the fluid) revealed a highly nontrivial dynamics: The impurity’s velocity experienced oscillations superimposed on a slowdown; finally the velocity apparently saturated at some non-zero value, vf [1,2]. These studies, while producing much excitement, left unanswered basic questions on the nature of the effects discovered. It was even unclear whether the incomplete relaxation was a finite-size effect or an effect present in the thermodynamic limit.

We present a detailed analytical study of the anomalous relaxation dynamics of an impurity particle injected in the one-dimensional quantum fluid [3-7]. In particular, we rigorously prove that the impurity particle of finite mass never stops completely, even in the thermodynamic limit [3,4]. This should be contrasted with the well-known absence of superfluidity in one dimension. These two facts can be reconciled since vf depends on the mass of the particle and vanishes for the infinite mass, which is equivalent to the absence of superfluid flow through a static constriction. We also find analytical dependence of the final velocity, vf, on the initial velocity, v0, for particular quantum fluids, the one-dimensional Fermi gas and the gas of impenetrable bosons [5-7].

[1] C. J. M. Mathy, M. B. Zvonarev, and E. Demler, “Quantum flutter of supersonic particles in one-dimensional quantum liquids,” Nature Physics 8, 881–886 (2012).
[2] M. Knap, C. J. M. Mathy, M. Ganahl, M. B. Zvonarev, and E. Demler, “Quantum flutter: Signatures and robustness,” Phys. Rev. Lett. 112, 015302 (2014).
[3] O. Lychkovskiy, “Perpetual motion of a mobile impurity in a one-dimensional quantum gas“, Phys. Rev. A 89, 033619 (2014).
[4] O. Lychkovskiy, “Perpetual motion and driven dynamics of a mobile impurity in a quantum fluid“, Phys. Rev. A 91, 040101 (Rapid Communication) (2015).
[5] E. Burovski, V. Cheianov, O. Gamayun, and O. Lychkovskiy, “Momentum relaxation of a mobile impurity in a one-dimensional quantum gas”, Phys. Rev. A 89, 041601 (Rapid Communication) (2014).
[6] O. Gamayun, O. Lychkovskiy, V. Cheianov, “Kinetic theory for a mobile impurity in a degenerate Tonks-Girardeau gas”, Phys. Rev. E 90, 032132 (2014).
[7] O. Gamayun, E. Burovski, V. Cheianov, O. Lychkovskiy, M. Malcomson, M. Zvonarev, in preparation.

Host: Boris Fine

Abstract:
Light absorbed by a semiconductor will create an excited electron and hole which, being oppositely charged, can bind into an atom-like state called an exciton. In the 1960s it was realized that, if the exciton binding energy were larger than the semiconductor band gap, excitons would have negative energy and, hence, spontaneously proliferate in equilibrium. The result was called an “excitonic insulator,” which is as a macroscopic condensate of electron‐hole pairs characterized by a redistribution of electronic charge, or charge‐density wave (CDW). Over the last 50 years, no experimental technique has unambiguously identified an excitonic insulator phase in any real material, despite many candidates being investigated. The reason is that its tell-tale signature—an electronic “soft mode” with finite momentum—could not be detected with any experimental technique. Here, I present data using a meV‐resolution, momentum‐resolved electron energy‐loss spectroscopy (M‐EELS) technique to study electronic modes in the transition metal dichalcogenide 1T‐TiSe₂. We find that, while the prevailing mode at room temperature is a conventional plasmon, near the onset temperature of CDW order it disperses to zero energy at finite momentum, as expected for an excitonic state. At lower temperatures, the excitation hardens and we interpret it as an amplitude mode of the excitonic condensate. These observations represent the strongest evidence of the existence of an excitonic insulator to date.

A series of joint research seminars of the Russian Quantum Centre and Skoltech Centre for Photonics and Quantum Materials will take place every Tuesday and Thursday between February 2, 2017 and February 16, 2017.
Below are the links to the RQC presentations.

https://drive.google.com/open?id=0BxgJuKZZ7xcIX0NTZVJmNEVSREk​
https://drive.google.com/open?id=0BxgJuKZZ7xcIX3dIR0ZSa0tQYlE​

Dr. Ivan Sherstov presents the concept of the joint Roscosmoc & Skoltech research laboratory for time and frequency”.

Abstract:
When different materials are interfaced/jointed with each other, the resulted hybrid systems often manifest fascinating physical properties that do not exist in nature. Among the many artificial hybrids (sometimes addressed as meta-materials or hetero-structures), nano-hybrid made with low-dimensional materials and other functional materials is attracting tremendous attentions in recent years.  In this talk, we will mainly go through a couple of examples of our recent progresses on the graphene/superconducting-islands, and the 2D materials/h-Boron-Nitride nano-hybrid systems. In the former, the superconducting behavior is successfully coupled to the gate-tunable feature of graphene, leading to a metal-superconducting quantum phase transition at the ground state. While in the later, ultra-flat and ultra-clean interface allow ballistic electronic transport, opening new path to realize the paradigm of electron optics. Our recent experimental progresses on MoS₂/h-BN hetero-structures will also be discussed. We expect that artificial nano-hybrids and their quantum properties can be expanded into many research areas that are important for both fundamental studies and future applications.
Brief Biography:
Zheng Vitto Han, research professor at the Institute of Metal Research, Chinese Academy of Sciences. Dr. Han has been utilizing nanoFab together with artificial staking methods to study the interfacial coupling of low-dimensional materials such as graphene and superconducting nano-dot arrays, MoS₂, and hexagonal boron nitrides (h-BN), etc. He has revealed a series of exotic physical properties of such systems, with the related works published in Sicence, Nature Physics, Nature Materials and other journals.

Lecture 1. Non-interacting systems
Monday, May 22, 14:00-17:00, room 303
Abstract:
In the first lecture we will focus on non-interacting disordered systems which exhibit Anderson localization and Anderson transitions. For the sake of simplicity and better solvability, we will only consider one-dimensional and quasi-one-dimensional systems (wires). We will develop basic theoretical tools to analyze such wires, including the scattering formalism (Landauer formula, DMPK equation), supersymmetry method, and saddle-point (instanton) method. We will also discuss the Altland-Zirnbauer classification of non-interacting disordered systems, which has become central in the modern subject of topological insulators.

Lecture 2. Interactions and many-body localization
Tuesday, May 23, 14:00-17:00, room 303
Abstract:
In the second lecture we will consider how to add interactions into account. This will lead us to consider the problem of Anderson localization on Bethe lattice, which was historically proposed in the context of the problem of the life time of single-particle excitations in quantum dots. Eventually, this was applied to the problem of many-body de-localization, which happens to be most interesting and relevant exactly in the (quasi-) one-dimensional geometry, and is the subject of intensive current research.

Brief Biography:
Ilya Gruzberg obtained his PhD at Yale University under the supervision of Nick Read in 1998. He then spent three years as a postdoc at KITP, Santa Barbara, and one year as a Pappalardo Fellow at MIT. In 2002 he became a faculty member in the physics department at the University of Chicago, and in 2013 moved to Ohio State University. Ilya’s research interests include disordered electronic systems, Anderson localization, quantum Hall effects, statistical and mathematical physics.

Abstract: The optics of surface electromagnetic waves (e.g. surface plasmon polaritons propagating along metal-dielectric interfaces and Bloch surface waves propagating along the interfaces between a photonic crystal and a homogeneous medium) nowadays is one of rapidly developing research topics in nanophotonics. For various applications, the design of on-chip optical elements (also called the elements of 2D optics) for steering the propagation of surface electromagnetic waves is of great interest. In the present talk, I will discuss several recent results of our research group in this field. In particular, planar analogues of near-wavelength high-contrast diffraction gratings for surface plasmon polaritons will be discussed. The possibility of creating high-efficiency grating-based plasmonic reflectors, beam splitters and deflectors with subwavelength or near-subwavelength footprint in the propagation direction will be demonstrated.
Theoretical, numerical and proof-of-concept experimental results will be presented.
Another type of on-chip nanophotonic elements under consideration are planar analogues of phase-shifted Bragg gratings for Bloch surface waves. The performance of these structures and their application to optical analog computing (optical computation of temporal and spatial derivatives of Bloch surface wave pulses and beams) will be discussed. We believe that the proposed on-chip structures may find application in the design of systems for optical information transmission and processing at the nanoscale.
Brief biography:
Evgeni A. Bezus graduated with honors from Samara State Aerospace University (SSAU, currently – Samara National Research University (Samara University)) in 2009, majoring in Applied Mathematics. In 2012 he defended his Candidate of Sciences (Ph. D.) thesis in Optics at SSAU. Currently, he is a Research Fellow at the Diffractive Optics Laboratory of the Image Processing Systems Institute — Branch of the Federal Scientific Research Centre “Crystallography and Photonics” of the Russian Academy of Sciences and an Associate Professor at the Technical Cybernetics Department at Samara University. His scientific interests include nanophotonics and plasmonics, as well as modal methods for the numerical solution of Maxwell’s equations.

Abstract: Liquid crystal (LC) devices for displays and photonics are dominating in the market and will be the basic technology for advanced display and electronics in the nearest 10 years. Photoalignment materials can be effectively used in LC alignment and patterning for new generations of LC devices that provide extremely high resolution and optical quality of alignment both in glass and plastic substrates, photonics holes etc. New liquid crystal devices include ORW E-paper, field sequential color ferroelectric liquid crystal (FLC) projectors, photo-patterned quantum rods and 100% polarizers, q-plates, sensors, switchable lenses, windows with voltage controllable transparency, security films, switchable antennas.
Brief biography:
Professor Chigrinov graduated from Faculty of Applied Mathematics, Moscow Electronics Institute, the Diploma of Engineer – Mathematician (MPhil) in 1973. In 1978, he obtained PhD degree in Solid State Physics (Liquid Crystals) in the Institute of Crystallography, USSR Academy of Sciences. In 1988, he becomes a Doctor of Physical and Mathematical Science and obtained a degree of a Professor in 1998. Since 1973, he was a Senior, Leading Researcher, and then Chief of Department in Organic Intermediates & Dyes Institute (NIOPIK). Since 1996 he was a Leading Scientist in the Institute of Crystallography, Russian Academy of Sciences and join HKUST in 1999, as an Associate Professor. He is a member of Editorial Board of “Liquid Crystals Today” since 1996 and Associate Editor of Journal of SID since 2005. He is an author of 2 books, 15 reviews and book chapters, 133 journal papers, 286 Conference presentations and 50 patents and patent applications in the field of liquid crystals since 1974. He is a Member of International Advisory Committee for Advanced Display Technology Conferences in Russia, Ukraine and Belarus since 1999, European SID Program Committee since 2004, International Advisory Board of International Liquid Crystal Conference since 2006.

Abstract:
The majority of the nanowire (NW) synthesis methods utilize catalyst particles to guide the nanowire geometry. In contrast, catalyst-free methods are attractive for facile fabrication of pure nanowires without the need for catalyst preparation. Nonetheless, how nanowire growth is guided without a catalyst is still widely disputed and unclear. We show that the nanowire growth during metal oxidation is limited by a nucleation of a new layer. On the basis of in situ transmission electron microscope investigations, using CuO NWs as a model material, we found that the growth occurs layer by layer at the lowest specific surface. Atomic layers nucleate at the edge of twin boundary ridges and form a long-range ordering along the twin boundary. energy planes. One can anticipate that it will be possible to use defects to drive and even control the process of growth and the geometry of nanowires in a similar manner to what can be done with the help of catalyst particles. Although we have investigated the formation of only CuO nanowires, similar growth mechanisms could be also extended to non-catalytic growth of other nanowires and ionic crystals grown by oxidation−reduction reactions. [1] Zinc oxide nanostructures have received broad attention due to their distinguished performance in electronics, optics, gas sensing and piezoelectronics. Zinc oxide tetrapod (ZnO-T) is one of these structures, consisting of 4 nanowires, is especially interesting for its simple synthesis, however growth mechanism is not thoroughly understood. Here, we propose a simple non-catalytic one-step process method for an efficient and rapid synthesis of ZnO tetrapods by Zn vapor oxidation under air environment and application for fast UV sensors and dye sensitized solar cells (DSSC). [2] 1. Rackauskas S, Jiang H, Wagner JB, et al., Nano letters 14, 10 (2014).
2. Rackauskas S, Klimova O, Jiang H, et al. J Phys Chem C 119, 28 (2015).
Brief Biography:
Dr. Simas Raskauskas obtained PhD degree – Doctor of science in technology – in Aalto University, Laboratory of Applied Physics, Finland. Thesis: Non-catalytic growth of metal oxide nanowires: properties and growth mechanism investigations. At present he is a Research fellow (Marie Curie actions) in University of Torino, Department of Chemistry, NIS Centre of Excellence, Italyю Dr. Raskauskas is an author of 26 peer-reviewed publications in: Nano Letters, ACS Nano, Nano Research, Applied Physics Letters, Nanotechnology, etc. Citing factor h-index is 7, with overall 311 citations (www.webofknowlegde.com). Scientific results were presented in over 20 international conferences, 1 as invited talk. 3 patent applications filed and 1 granted.

Abstract:
Three-level systems have attracted considerable interest since they allow to study quantum interference phenomena, such as coherent population trapping (CPT), electromagnetically induced transparency (EIT), and Autlers-Townes (AT) splitting. We study frequency mixing of two coherent waves on a three-level artificial atom – a superconducting quantum circuit. Here we present direct experimental observation of the coherent emission and thus coherent frequency conversion of a cyclic three-level artificial atom driven by two external fields. The fundamental difference of mixing on the quantum system from classical frequency conversion is that the coherent emission is at a single frequency. We find that the pattern of coherent emission from the atom depends on all decay rates and field strengths. We investigate the direction of splitting of the coherent emission for various combinations of powers of the two external drives as a function of detuning. Finally, we demonstrate that our experimental results are in good agreement with numerical simulations based on the master-equation formalism.
Brief Biography:
Teresa Hönigl-Decrinis is a PhD student at Royal Holloway, University of London. Thesis Title: Quantum Optics on Artificial Quantum Media, Supervisor: Professor Oleg Astafiev.  

Abstract:
With the rise of nanotechnology Mie theory has shown once again to be a very useful tool both for fundamental and applied research. I am going to present some recent advances for evaluating the near-field of multilayered spherical nanoparticles. Combining Mie theory and stochastic optimization opens a way to design multilayered nanoparticles with desired optical properties. By using this approach two examples are provided.
The first one is “invisibility” coating, which is able to significantly reduce total scattering from the nanoparticle. The second example is about superabsorption when the absorption cross-section of the nanoparticle can reach the theoretical limit for several modes at the same frequency. This becomes possible when several resonant modes of the structure overlap at the same frequency, and this regime can be achieved in multilayered nanoparticles.
Personal profile
At present Konstantin Ladutenko is a PhD student at ITMO. He was involved in a scientific research at the Ioffe Institute since his high school as an intern, and after his graduation from the Saint-Petersburg State Polytechnical University – as a research scientist. In 2011, he took to a position in ITMO University. Konstantin has a good knowledge of semiconductor physics and a lot of experimental experience with atomic-force microscopy. His research interests are in the areas of numerical methods and simulation in physics, with a focus on Mie theory and stochastic optimization.

Russian-German young scientists seminar “Nanomaterials and scattering methods” in ongoing event that takes place one year in Russia, the next year – in Germany. Every year the participants visit research institutes in different cities in order to be acquainted with cutting-edge research and modern laboratory facilities, and also to present and to discuss their research and projects.

This year the seminar is launched in Yekaterinburg, Russia on September 10, 2017; the visit to Skoltekh is scheduled for September 20, 2017. Skoltech will visit 29 invited participants of the Russian-German seminar: 14 students / graduate students and 2 professors from Germany, 12 students / graduate students and 1 professor from Russia.

The purpose of the event in Skoltech is to get acquainted with the nanomaterials research studies and methods used in Skoltech, to present the laboratories of the Center for Photonics and Quantum Materials, and to initiate exchange of views and collaboration between Skoltech young scientists and the guests – seminar participants.

The Preliminary programme:

Time	Programme activity
09:45 – 10:00	Opening in Skolkovo Institute of Science and Technology – Welcome address of CPQM Director Prof. Ildar Gabitov
10:00 – 10:15	Prof. Ildar Gabitov, overview of Skoltech centre for Photonics & Quantum Materials research
10:15 – 10:45	Dr. Sergei Kosolobov, Presentation of modern research methods & techniques
10:45 – 11:00	Coffee-break
11:00 – 12:30	Guided tour to Skoltech labs (participants are divided in 2 groups, each visits Nanomaterials Laboratory (Skoltech guides Evgeniya Gilshtein & Vsevolod Iakovlev) and Hybrid Photonics Laboratory (Skoltech guides Mael Brossard & Anton Zasedatelev)
12:30 – 13:30	Lunch
	Presentation and discussion of RGYS seminar participants’ projects
13:30 – 14:00	23– Irina Dorosheva “Optical properties of titania nanotubular structure prepared by anodization”
14:00 – 14:30	24– Fabian Nehr “Graphene electronics: application and fabrication”
14:30 – 15:00	1– Yaroslav Biryukov “High-temperature Mössbauer spectroscopic and X-Ray diffraction study of Fe3O2(BO4)”
15:00 – 15:30	Coffee break
15:30 – 16:00	20– Theresa Nemeth “Titanium dioxide and zinc oxide nanoparticles in sunscreens”
16:00 – 16:30	21– Sabrina Thomä “Protein-Assisted Self-Assembly of Raspberry like Core/Satellite Nanoclusters”
16:30 – 17:30	22– Julia Ariko “Mechanically tuned nanocomposite coating on titanium metal with integrated properties of biofilm inhibition, cell proliferation, and sustained drug delivery”