Condensed Matter Physics Seminar
2006/2007 | 2007/2008 | 2008/2009 | 2009/2010 | 2010/2011 | 2011/2012 | 2012/2013 | 2013/2014 | 2014/2015 | 2015/2016 | 2016/2017 | 2017/2018 | 2018/2019 | 2019/2020 | 2020/2021 | 2021/2022 | 2022/2023 | 2023/2024 | 2024/2025
2018-06-08 (Friday)
room 1.02, Pasteura 5 at 12:15 
Grigory Tkachov (University of Wuerzburg)Probing topology by quantum transport
Topological insulators are characterized by a skyrmion-like (pseudo)spin texture of electronic bands in momentum space, giving rise to nontrivial Chern numbers and gapless edge states. This talk will explore an intricate connection between the nontrivial band topology and quantum electron transport in some representative topological systems. I will in particular address the topological aspects of the minimal conductivity, backscattering processes, weak antilocalization and the universal magnetoeletric effect in HgTe as well as unconventional triplet superconductivity and Majorana fermions in candidate topological superconductors.
2018-05-11 (Friday)
room 1.02, Pasteura 5 at 12:15
Jan Zaanen (Leiden University)Quantum thermalization and the unparticle physics of strange metals
2018-04-27 (Friday)
room 1.02, Pasteura 5 at 12:15
Timo Hyart (MagTop Warsaw)Interplay of spontaneous symmetry breaking and topology in condensed matter systems
Significant progress in understanding of the low-energy properties of quantum matter has been achieved using the concepts of spontaneous symmetry breaking and topological invariants separately. In this talk, I will discuss the physics of interacting systems where the relationship of these two concepts is subtler, so that the order parameters associated with the spontaneous symmetry breaking are linked to the momentum space topology. I will consider three examples of systems where such kind of interplay is important: band-inverted electron-hole bilayers, helical quantum Hall exciton condensates and flat-band superconductivity in topological semimetals. I will discuss some of the exotic properties of these systems and some general ideas for designing symmetry-broken phases by utilizing the interplay of topology and interactions.
2018-04-20 (Friday)
room 1.02, Pasteura 5 at 12:15
Wojciech Grochala (CENT UW)Silver route to cuprate analogs
Silver(II) fluorides are represented by over a hundred distinct stoichiometries, and rich crystal chemistry, but due to their high reactivity they are often viewed as exotic even by chemists. The interest in these materials from solid state physics and materials point of view stems from extremely strong magnetic superexchange interactions which they may host, substantial magnetic anisotropy, as well as possibility of generating superconductivity in two-dimensional fluoroargentate(II) systems, as outlined in a recent contribution. The new experimental and theoretical findings for selected silver(II) fluorides will be presented in this talk, combining both chemistry and physics perspectives.
2018-04-13 (Friday)
room 1.02, Pasteura 5 at 12:15
Charles Downing (Universidad Autónoma de Madrid)Topological states and collective Lamb shifts in plasmonic nanoparticle chains
One of the primary goals of plasmonics is to confine light at subwavelength scales. This aim is motivated by the desire to both transport and manipulate light over macroscopic distances. Here we investigate collective plasmonic modes in chains of spherical metallic nanoparticles, which are coupled by near-field interactions. Using an open quantum system approach in which the collective plasmons are interacting with vacuum electromagnetic modes, we analytically evaluate the resulting radiative frequency shifts of the plasmonic bandstructure. This is a remarkable manifestation of the collective Lamb shift in a nanoplasmonics setting. We go on to consider a dimerization of the nanoparticle chain, which leads to the emergence of topological plasmonic edge states, as codified by a nontrivial Zak phase. These exotic edge states are found to be robust against long-range quasistatic interactions, bosonic statistics, retardation effects and non-resonant coupling terms.
2018-04-06 (Friday)
room 1.02, Pasteura 5 at 12:15
Jan Dereziński (KMMF WF UW)Almost homogeneous Schr\"odinger operators
I will discuss the theory of Schr\"odinger operators with 1/x^2 potentials.This is a class of objects with surprisingly rich mathematical phenomenology, which should be close to physicists' hearts: the "running coupling constant" flows under the action of the "renormalization group", there are two "phase transitions", attractive and repulsive fixed points, limit cycles, breakdown of conformal symmetry, etc. I will discuss both the self-adjoint and non-self-adjoint cases. The latter have quite curious properties and I am looking for their physical applications.
2018-03-23 (Friday)
room 1.02, Pasteura 5 at 12:15
Marcin Napiórkowski (KMMF WF UW)On the critical temperature in an interacting Bose gas
I will discuss the question how the presence of interactions changes the critical temperature of a Bose--Einstein condensate. I will present results obtained within a variational Bogoliubov model both in 2 and 3 dimensions.
2018-03-16 (Friday)
room 1.02, Pasteura 5 at 12:15
Miłosz Panfil (IFT UW)Edge singularities and quasi-long-range order in non-equilibrium steady states
The singularities of the dynamical response function are one of the most remarkable effects in many-body interacting systems. However in one dimension these divergences only exist strictly at zero temperature, making their observation very difficult in most cold atomic experimental settings. Moreover the presence of a finite temperature destroys another feature of one-dimensional quantum liquids: the real space quasi-long-range order in which the spatial correlation functions exhibit power-law decay. We consider a non-equilibrium protocol where two interacting Bose gases are prepared either at different temperatures or chemical potentials and then joined. We show that the non-equilibrium steady state emerging at large times around the junction displays edge singularities in the response function and quasi-long-range order.
2018-03-09 (Friday)
room 1.02, Pasteura 5 at 12:15
Hiroyuki Yamase (Tsukuba, Japan)Incommensurate magnetic order in the Hubbard model and its possible connection to high-Tc cuprate superconductors
The ground state of the two-dimensional Hubbard model is analyzed by including a possible incommensurate spiral order by using a functional renormalization group scheme and mean-field theory. We discuss a connection to the drop of the Hall number and quantum oscillation measurements in high-Tc cuprate superconductors. Details are seen in PRL 116, 096402 (2016) and PRL 117, 187001 (2016).
2018-02-02 (Friday)
room 1.02, Pasteura 5 at 12:15
P.G.Silvestrov (TU Braunschweig)Wigner crystal phases in bilayer graphene
It is generally believed that a Wigner Crystal in single layergraphene can not form because the magnitudes of the Coulombinteraction and the kinetic energy scale similarly with decreasingelectron density. However, this scaling argument does not hold forthe low energy states in bilayer graphene. We consider theformation of a Wigner Crystal in weakly doped bilayer graphenewith an energy gap opened by a perpendicular electric field. Weargue that in this system the formation of the Wigner Crystal isnot only possible, but different phases of the crystal with verypeculiar properties may exist here depending on the systemparameters.