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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.

09 de diciembre de 2021, 12:00 h. online

Matter in non-perturbative cavity QED

David Zueco
Instituto de Nanociencia y Materiales de Aragn CSIC and Universidad de Zaragoza

In this seminar, we discuss the theory of a general material system of N particles coupled to a cavity. We focus on equilibrium. We use bounds for the partition function and a a coherent-state path integral formulation. We obtain the exact (non-local) action wherethe photonic degrees of freedom are replaced by an effective position-dependent interaction between the particles. Besides, in the large-N limit, we show that the theory can be cast into an effective Hamiltonian where the cavity induced interactions are made explicit. We showcase the descriptive power of the formalism with three examples: photon condensation, the 2D free electron gas in a cavity and the modification of magnetic interactions between molecular spins; recovering, condensing and extending some recent results in the literature. We delve into the example of modifying magnetic interactions anticipating the first experimental steps.

02 de diciembre de 2021, 12:00 h. online

Bound states in the continuum, hybrid modes and pattern formation in one dimensional nonlinear resonators

Alexey Yulin
Department of Nanophotonics and Metamaterials ITMO University, Saint-Petersburg

In this talk I discuss nonlinear periodically corrugated one-dimensional waveguides pumped at normal incidence by coherent light. It is known that these systems can support so called Bound States in the Continuum (BIC) localized states with their frequency lying within the spectrum of free propagating waves. These states cannot be excited by incident radiation but have high Q factor (it is infinite for perfect BIC and in the absence of material losses). We discuss parametric excitation of the BIC mode, the formation of hybrid states and the dynamics of different nonlinear structures nestling on the hybrid states. In particular, domain walls, their bound states forming dark dissipative solitons and bright dissipative solitons are addressed.

Papers related to the talk:

1. D. Dolinina and A. Yulin, Spontaneous symmetry breaking of nonlinear states in optical cavities with radiative losses, Optics Lett. 45, 3781, (2020).

2. D. Dolinina and A. Yulin, Dissipative switching waves and solitons in the systems with spontaneously broken symmetry, Phys. Rev. E 103, 052207 (2021).

25 de noviembre de 2021, 12:00 h. Saln de Actos

Extremely long range Josephson effect across a half metallic ferromagnet

Jacobo Santamara
Universidad Complutense de Madrid

*also online

The Josephson effect results from the coupling of two superconductors across a non-superconducting spacer to yield a quantum coherent state. In ferromagnets, singlet (opposite-spin) Cooper pairs decay over very short distances, and thus Josephson coupling requires a nanometric spacer. This is unless equal-spin triplet pairs are generated which, theoretically, can couple superconductors across much longer distances. Despite many experimental hints of triplet superconductivity at ferromagnet/superconductor interfaces, long range triplet Josephson effects across ferromagnetic barriers have remained elusive. In this talk I will discuss a micron-range Josephson coupling in planar junctions across the half-metallic ferromagnet La0.7Sr0.3MnO3 combined with the high-temperature superconductor YBa2Cu3O7. These display the hallmarksof the Josephson physic, namely critical current oscillations due to flux quantization (Fraunhofer pattern) and phase locking under microwave excitation (Shapiro steps) [1]. The marriage of high-temperature quantum coherent transport and full spin polarization brings unique opportunities for the practical realization of superconducting spintronics, and enables novel strategies for devices in quantum technologies.

[1] Nature Mater (2021), in print

Work done in collaboration with D. Sanchez-Manzano, S. Mesoraca, F. Cuellar, M. Cabero, V. Rouco, G. Orfila, X. Palermo, A. Balan, L. Marcano, A. Sander, M. Rocci, J. Garcia-Barriocanal , F. Gallego, J. Tornos, A. Rivera, F. Mompean., M. Garcia-Hernandez, J. M. Gonzalez-Calbet, C. Leon, S. Valencia, C. Feuillet-Palma, N. Bergeal, A.I. Buzdin, J. Lesueur, Javier E. Villegas, J. Santamaria.

1 GFMC. Dept. Fisica de Materiales. Facultad de Fisica. Universidad Complutense. 28040 Madrid

2 Unit Mixte de Physique, CNRS, Thales, Universit Paris-Saclay, 91767 Palaiseau. France

3 Centro Nacional de Microscopia Electronica. Universidad Complutense 28040 Madrid.

4 Helmholtz-Zentrum Berlin fr Materialien und Energie, Albert-Einstein-Strasse 15, D-12489, Berlin, Germany

5 Characterization Facility, University of Minnesota, 100 Union St, Minneapolis, MN 55455, USA

6 Instituto de Ciencia de Materiales de Madrid ICMM-CSIC 28049 Cantoblanco. Spain

7 Laboratoire de Physique et dEtude des Matriaux, CNRS, ESPCI Paris, PSL Research University, UPMC, 75005, Paris, France

8 Universit Bordeaux, CNRS, LOMA, UMR 5798, F-33405 Talence, France

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).

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

Plasmonic Instabilities in two-dimensional Dirac Materials

Hugo Teras
Instituto de Plasmas e Fuso Nuclear, Instituto Superior Tcnico, Universidade d

The generation of coherent terahertz radiation is an outstanding challenge at both scientific and technological levels. In one hand, the quest for table-top THz solutions based on integrated-circuit technology puts graphene and other bi-dimensional in the run. Plasma instabilities in bi-dimensional materials are an appealing mechanism for the production of low-power coherent THz signals. In this talk, we discuss how to produce plasmonic instabilities based on electronic injection only.

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

High Harmonic Spectroscopy of Strongly Correlated and Topological Materials

Rui E.F. Silva
Instituto de Ciencia de Materiales de Madrid ICMM-CSIC

The recent discovery of high harmonic generation in solids, merging the fields of strong field and condensed matter physics, opened the door for the direct observation of Bloch oscillations, all-optical reconstruction of the band structure and direct observation of the influence of the Berry curvature in the optical response. In this work, we will focus on high harmonic generation in strongly correlated and topological materials. First, I will show how high harmonic spectroscopy can be used to induce and time resolve insulator-to-metal transitions in strongly correlated materials, using the Hubbard model. I will further demonstrate how high harmonic spectroscopy can be used to identify topological phases of matter and how the Berry curvature leaves its fingerprint in the nonlinear optical response of the material. Using a combination of w-2w counter-rotating strong circular fields, we demonstrate that we are able to induce valley polarization in hexagonal 2D materials and use HHG spectroscopy to read the valley polarization. At last, I will show how the use of Wannier orbitals can be useful in the calculation of the nonlinear optical response of solids.

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