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Seminarios y Eventos

Seminars and Events

Joint Seminar Series ICMM+IFIMAC Condensed Matter @Cantoblanco

ICMM Coordinators: Elsa Prada, Mara Jos Caldern, Ramn Aguado, Sigmund Kohler

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Find previous seminars in our Youtube channel.

18 de noviembre de 2021, 12:00 h. online

Cavity-induced single-photon wavefunction engineering

Simone De Liberato
School of Physics and Astronomy, University of Southampton

When the coupling between a confined electromagnetic mode and the electronic degrees of freedom of a solid-state system becomes large enough, the interaction can modify the electronic wavefunctions and the related material properties. These effects become more dramatic in systems with continuum electronic degrees of freedom, in which the gapless spectra enhance the electronic malleability.

Solid-state cavity quantum electrodynamics can thus become a tool for quantum material engineering, allowing us to drastically enrich the catalogue of materials available for scientific and technological applications.

In this talk I will present the first experimental demonstration of cavity-induced single-photon wavefunction modification in which we measured a change of 30\% for the Bohr radius in microcavity embedded quantum wells [1]. Using doped quantum wells characterised by a continuum spectrum we then predicted [2] and demonstrated [3] the formation of novel excitons bound by photon exchange. We also observed related polaritonic nonlocal effects [4] reducing the achievable field enhancement and thus the achievable strength of the light-matter coupling.

[1] Experimental verification of the very strong coupling regime in a GaAs quantum well microcavity. S. Brodbeck et al., Phys. Rev. Lett. 119, 027401 (2017)

[2] Strong coupling of ionising transitions. E. Cortese et al., Optica 6, 354 (2019)

[3] Excitons bound by photon exchange. E. Cortese et al., Nature Physics 17, 31 (2021)

[4] Polaritonic nonlocality in light-matter interaction.S. Rajabali et al., Nature Photonics 15, 690 (2021).

28 de octubre de 2021, 12:00 h. online

Strong light-matter coupling: from transition metal dichalcogenides to Casimir self-assembly

Timur Shegai
Department of Physics, Chalmers University of Technology, Gothenburg, Sweden

Strong light-matter interactions are at the core of many electromagnetic phenomena. In this talk, I will give an overview of several nanophotonic systems which support polaritons - hybrids between light and matter, as well as try to demonstrate their potential usefulness in applications. I will start with transition metal dichalcogenides (TMDs) and specifically discuss one-dimensional edges in these two-dimensional materials. I will show that TMDs can be etched along certain crystallographic axes, such that the obtained edges are nearly atomically sharp and exclusively zigzag-terminated, while still supporting polaritonic regime. Furthermore, I will show that Fabry-Perot resonators, one of the most important workhorses of nanophotonics, can spontaneously form in an aqueous solution of gold nanoflakes. This effect is possible due to the balance between attractive Casimir-Lifshitz forces and repulsive electrostatic forces acting between the flakes. There is a hope that this technology is going to be useful for future developments in self-assembly, nanomachinery, polaritonic devices, and perhaps other disciplines.

21 de octubre de 2021, 12:00 h. online

Quantum devices and quantum materials: Single nanotube mechanics and quantum electronics

Andreas Httel
University of Regensburg, Germany

Single wall carbon nanotubes are in many respects an outstanding model system. From transport spectroscopy, ferromagnet/superconductor-nanotube hybrid devices, and nano-electromechanics all the way to microwave optomechanics, the work of my group covers by now a wide range of topics. I intend to present a select number of recent highlights.

In particular, by placing a vibrating carbon nanotube next to a superconducting coplanar microwave resonator at cryogenic temperature, one obtains a fundamentally new microwave optomechanical system. Electronic tunneling through well-defined quantum states dominates its behaviour. We have demonstrated a strongly enhanced, gate-controllable optomechanical coupling. With this, the manipulation of a carbon nanotube at the quantum limit of motion enters technological reach.

14 de octubre de 2021, 12:00 h. online

Correlated twisted spinorbitronics and heavy-fermions in van der Waals heterostructures

Jos Lado
Aalto University, Finland

Twisted van der Waals heterostructures provide an outstanding platform to create emergent physics, due to the possibility of combining materials with genuinely different electronic orders and the ability to enter controllable correlated states through twist engineering. Two-dimensional magnetic materials add a whole new set of opportunities, bringing up the unique ability to exploit exchange proximity effects to tailor the internal spin structure of an electronic state. Here we show that twisted heterostructures based on graphene, transition metal dichalcogenides, and two-dimensional magnetic materials provide a unique platform to create controllable correlated states. We will show how ferromagnetic two-dimensional materials allow designing new correlated states of matter in twisted graphene bilayers [1] and control symmetry breaking in twisted Janus dichalcogenide layers [2]. Furthermore, we will show how specifically designed twisted van der Waals heterostructures give rise to emergent heavy fermion physics [3,4], bringing to the twisted van der Waals world the physics of rare-earth compounds. These results put forward magnetic twisted two-dimensional materials as a rising knob to engineer and control a whole new family of correlated physics in moire van der Waals heterostructures.

[1] T. M. R. Wolf, O. Zilberberg, G. Blatter, and J. L. Lado, Phys. Rev. Lett. 126, 056803 (2021)

[2] D. Soriano and J. L. Lado, New J. Phys. 23 073038 (2021)

[3] A. Ramires and J. L. Lado, Phys. Rev. Lett. 127, 026401 (2021)

[4] V. Vaňo, M. Amini, S. C. Ganguli, G. Chen, J. L. Lado, S. Kezilebieke, P. Liljeroth, arXiv:2103.11989 (2021)

30 de septiembre de 2021, 12:00 h.

Exploring spin physics with topological materials

Hugo Dil
Institute of Physics, Ecole Polytechnique Fdrale de Lausanne

*This talk will also be streamed online.

Topological materials have attracted much attention in recent years because of the promises for spintronics and quantum technology. With the ever increasing number of materials and topological phases it can be helpful to take a step back and look what has been learnt so far. In this seminar I will give an overview of our results obtained for a variety of topological materials with a strong focus on their spin properties as explored by spin- and angle-resolved photoemission spectroscopy (SARPES). Besides directly imaging the topological protection mechanism, the apparent discrepancy between the measured and intrinsic spin polarisation will be explained for topological insulators by the concept of spin interference. Further, systems ranging from a topological Kondo insulator, to various types of Weyl semimetals, higher-order TIs, and triple fermions will be explored. It will be argued that although topology is a magnificent concept for the classification of condensed matter, it is far less exotic as often made to believe.

27 de septiembre de 2021, 12:00 h. Saln de Actos

Antiferromagnetic Insulatronics: Spintronics without magnetic fields

Mathias Klui, IEEE Magnetics Society Distinguished Lecturer
Johannes Gutenberg-University Mainz, and Centre for Quantum Spintronics, NTNU

*This talk will also be streamed online.

While known for a long time, antiferromagnetically ordered systems have previously been considered, as interesting but useless. However, since antiferromagnets potentially promises faster operation, enhanced stability and higher integration densities, they could potentially become a game changer for new spintronic devices. Here I will show how antiferromagnets can be used as active spintronics devices by demonstrating the key operations of reading [1], writing [2], and transporting information [3] in antiferromagnets.

[1] S. Bodnar et al., Nature Commun. 9, 348 (2018); L. Baldrati et al., PRL 125, 077201 (2020)

[2] L. Baldrati et al., Phys. Rev. Lett. 123, 177201 (2019); H. Meer et al., Nano Lett. 21, 114 (2020)

[3] R. Lebrun et al., Nature 561, 222 (2018). R. Lebrun et al., Nature Commun. 11, 6332 (2020).


ICMM-2021 - Sor Juana Inés de la Cruz, 3, Cantoblanco, 28049 Madrid, España. Tel: +34 91 334 9000. info @ icmm.csic.es