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
2023-11-10 (Friday)
room 1.02, Pasteura 5 at 12:15 
Luis. A. Peña Ardila (Univ. of Camerino)Catalyzation of supersolidity in Dipolar Binary Mixtures
Breakthrough experiments have newly explored the fascinating physics of dipolar quantum droplets and supersolids. The recent realization of dipolar mixtures opens further intriguing possibilities. We show that under rather general conditions, the presence of a second component catalyzes droplet nucleation and supersolidity in an otherwise unmodulated condensate. For miscible mixtures, droplet catalyzation results from the effective modification of the relative dipolar strength and may occur even for a surprisingly small impurity doping. We show that different ground-states may occur, including the possibility of two coexisting interacting supersolids.In addition, we predict the existence of a binary supersolid state in which the two components form a series of alternating domains, producing an immiscible double supersolid. Remarkably, we find that a dipolar component can even induce supersolidity in a nondipolar component. In stark contrast to single-component supersolids, the number of crystal sites is not strictly limited by the condensate populations, and the density is hence, substantially lower. Our results are applicable to a wide range of dipole moment combinations, marking an important step towards long-lived bulk-supersolidity as well as the possibility of studying polaron physics.
2023-11-03 (Friday)
room 1.02, Pasteura 5 at 12:15
Magdalena Birowska (IFT FUW)Optical properties of van der Waals layered antiferromagnets
Atomically thin, magnetic materials have recently gained a lot of attention in the field of two-dimensional (2D) materials. Single magnetic layers with critical temperature above room-temperature are extremely attractive for fundamental studies and promising candidates for future spintronic applications. However, probing the magnetic order of the 2D systems by conventional magnetic experimental setups is very challenging. On the other hand, it is well known that even in the single layer limit, semiconducting two-dimensional materials strongly absorb light. Therefore, optical spectroscopy is a good method for their characterization. In order to shed light on the intriguing phenomena of 2D antiferromagnets (AFM), I will present our recent theoretical investigations in the framework of the density functional theory (DFT) considering optical properties of the layered materials. In particular, I will focus on the representative AFM family, transition metal phosphorus trisulfides (MPX3), in respect to other 2D materials. I will cover currently puzzling research issues in respect to optical properties of layered materials.
2023-10-27 (Friday)
room 1.02, Pasteura 5 at 12:15
Paweł Ziń (NCBJ)Quantum droplets above local density approximation
2023-10-20 (Friday)
room 1.02, Pasteura 5 at 12:15
Maciej Maśka (Politechnika Wrocławska)Topological superconductivity driven by self-organized spin structures
We study the temperature-dependent self-organization of magnetic moments coupled to itinerant electrons in finite-size low-dimensional nanostructures proximitized to a superconducting reservoir. At low temperatures, an effective Ruderman-Kittel-Kasuya-Yosida-type interaction between localized magnetic moments mediated by itinerant electrons leads to their helical ordering. This ordering in turn affects the itinerant electrons, inducing a topologically nontrivial superconducting phase that hosts Majorana end mods. Calculations show that the topological state can exist at least for a chain of magnetic atoms and for a ladder. It is interesting to note that in the case of a ladder, an unconventional topological phase transition with neither gap closing nor a change of symmetry is possible. This contradicts the common assumption that topological phase transitions in topological superconductors are accompanied by a closing of the topological gap or a change of the symmetry of the system.
2023-10-13 (Friday)
room 1.02, Pasteura 5 at 12:15
Krzysztof Myśliwy (IFT UW)The polaron in Thomas—Fermi theory
We construct the simplest density functional for the problem of a single impurity interacting with a Fermi gas via a long–ranged potential using the Thomas–Fermi approach. We find that the Fermi polaron is fully bosonized in two dimensions, as the model results in a suitable Landau–Pekar functional known from the Bose polaron problem, and its multi—imaged version in other dimensions. We discuss applications of our theory for the 2d exciton–polaron and the ionic polaron problem and compute the effective mass for these cases, finding a self–trapping transition with order depending on the dimensionality.