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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.

25 de marzo de 2021, 12:00 h. online

Scaling silicon-based quantum computers using CMOS technology

Fernando Gonzlez-Zalba
Quantum Motion Technologies

The spins of isolated electrons in silicon are one of the most promising solid-state systems on which to implement quantum information processing. With the recent demonstrations of long coherence times, high-fidelity spin readout, and one- and two-qubit gates, the basic requirements to build a quantum computer have been fulfilled. Now, scaling the technology to a number of qubits sufficiently large to perform computationally relevant calculations is one of the major objectives and several proposals for large scale integration have been put forward.

Recently, important developments in the field of nanodevice engineering have shown that qubits can be manufactured in a similar fashion to field-effect transistors (FET), creating an opportunity to leverage the scaling capabilities of the semiconductor industry to address the challenge. Quantum computing with silicon transistors fully profits from the most established industrial technology to fabricate large scale integrated circuits while facilitating the integration with conventional electronics for fast data processing of the binary outputs of the quantum processor.
In this talk, I will present a series of results on CMOS transistors at milikelvin temperatures that show this technology could provide a platform on to which implement electron-spin qubits. I will specially concentrate on our efforts to develop a qubit specific measurement technique that is accurate and scalable while being compatible with the industrial fabrication processes. With that, I will show the first measurements of an electron spin in a silicon industry-fabricated device and finally, I will present results on how digital and quantum devices can be combined with this technique to time-multiplex the readout of several qubits.

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

Quantum thermoelectrics: using interference, entanglement and non-equilibriumness

Rafael Snchez
Departamento de Fsica Terica de la Materia Condensada, Universidad Autnoma de

Electrons in a conductor react not only to voltage but also to temperature gradients. In their motion, they carry electric charge as well as energy. This makes it possible to think of devices that are absorb excess heat from their environment and convert it into useful power. This can be done in three terminal devices: Two terminals support the charge current with the third one serving as the heat source, enabling the separation of charge and heat flows. Mesoscopic (nanoscale) systems are good candidates for this, because of their high degree of tunability and rich variety of different effects that allow for the mechanism of heat to power conversion: Coulomb interactions [1], resonant tunneling [2], entanglement [3], quantum interference, or the absence of thermalization [4]. I will review recent proposals and experimental implementations of three terminal energy harvesters.

[1] R. Snchez, M. Bttiker, Phys. Rev. B 87, 075312 (2011); H.
Thierschmann et al., Nature Nanotech. 10, 854 (2015); B. Roche et al., Nature Comm. 6, 6738 (2015).
[2] A. N. Jordan, B. Sothmann, R. Snchez and M. Bttiker, Phys. Rev. B 87, 075312 (2013); G. Jaliel et al., Phys. Rev. Let. 123, 117701 (2019).
[3] R. Snchez,P. Burset, and A. L. Yeyati, Phys. Rev. B 98, 241414 (2018).
[4] R. Snchez, J. Splettstoesser and R. S. Whitney, Phys. Rev. Lett. 123, 216801 (2019)

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

Colloidal design: building molecules and materials at the micro- and nanometer scale

Peter Schall
Institute of Physics University of Amsterdam, Netherlands

Recent breakthroughs in the synthesis and design of colloidal building blocks allow the assembly of complex structures with unprecedented control over their architecture. In particular, patchy particles exhibiting highly directional interactions enable the assembly of colloidal molecules, and colloidal graphene, analogues of the atomic compounds at the colloidal scale. Such assembly control promises fascinating applications in the design of new functional materials at micrometer and nanometer length scales. In this talk, I will show how the combination of patchy particles and solvent-mediated interactions enables new control in the directional bonding that can be explored to build colloidal molecules and investigate their assembly kinetics and reactions. Using tetramer particles, we assemble colloidal analogs of well-known sp3-hybridized carbon compounds such as (cyclo)butane, butyne, cyclopentane, and cyclohexane, and investigate their transition states. Adsorbed at an attractive substrate, these particles assemble into two-dimensional materials such as graphene. This control applied to the nanoscale can assemble quantum dots, leading to new electronic states useful for active films in optoelectronic devices. These results demonstrate the opportunities for applications and exciting new science that can be explored with these novel colloidal architectures.

25 de febrero de 2021, 12:00 h. online

Evolution in uses of Antimony: from ancient Egyptian queen make-up to new 2D-materials

Flix Zamora
Departmento de Qumica Inorgnica, Institute for Advanced Research in Chemical Sciences (IAdChem), and Condensed Matter Physics Center (IFIMAC), Universidad Autnoma de Madrid.

In the search for 2D semiconductor materials, our research group and others have recently pointed out that antimonene, i.e. single or few-layer antimony, can be an interesting option. This seminar will aim to provide a perspective revision of our results on antimonene. I will describe several preparation methods developed in our group to prepare this material, going from top-down procedures, such as micromechanical exfoliation, which allows the isolation of monoatomic layers, or liquid phase exfoliation, to bottom-up synthesis that provides a way to produce large quantities of high-quality few-layer antimonene. Some selected physical and chemical properties found for the isolated antimonene materials will be discussed. Finally, I will show the first results obtained in the exfoliation of 3D covalent crystals, alpha-germanium, which opens new avenues for the 2D-materials.

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

Unconventional superconductivity in two-dimensional Van der Waals materials

Miguel M. Ugeda
Donostia International Physics Center (DIPC), Paseo Manuel de Lardizbal 4, 20018 San Sebastin, Spain.

Van der Waals materials provide an ideal platform to explore superconductivity in the presence of strong electronic correlations, which are detrimental of the conventional phonon-mediated Cooper pairing in the BCS-Eliashberg theory and, simultaneously, promote magnetic fluctuations. Despite recent progress in understanding superconductivity in layered materials, the glue pairing mechanism remains largely unexplored in the single-layer limit, where electron-electron interactions are dramatically enhanced. In this talk, I will present experimental evidence of unconventional Cooper pairing mediated by magnetic excitations in monolayers of Se-based transition metal superconductors (NbSe2 and TaSe2), two model strongly correlated 2D materials. 2D TMD materials will reduce the enormous complexity associated with the investigation of unconventional superconductivity, and will rapidly allow us to expand our current limited knowledge of non-phononic Cooper pairing. They offer unprecedented simplicity for modelling as compared to the most studied bulky unconventional superconductors, i.e., cuprates, Fe-pnictides and heavy-fermion compounds. In two dimensions, TMD superconductors are even simpler to model than twisted bilayer graphene, where superconductivity is intrinsically linked to specific magic angles. From the experimental point of view, our work opens the tantalizing possibility to explore unconventional superconductivity in simple, scalable and widely accessible 2D materials.

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

From Andreev to Majorana bound states in hybrid superconductor semiconductor nanowires

Elsa Prada
Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC)

Electronic excitations above the ground state must overcome an energy gap in superconductors with spatially-homogeneous s-wave pairing. In contrast, inhomogeneous superconductors such as those with magnetic impurities or weak links, or heterojunctions containing normal metals or quantum dots, can host subgap electronic excitations that are generically known as Andreev bound states (ABSs). With the advent of topological superconductivity, a new kind of ABS with exotic qualities, known as Majorana bound state (MBS), has been discovered. In this talk, I will focus on hybrid superconductor-semiconductor nanowires as one of the most flexible and promising experimental platforms to study ABSs and MBSs. I'll discuss how the combined effect of spin-orbit coupling and Zeeman field in these wires triggers the transition from ABSs into MBSs. I'll show theoretical progress beyond minimal models in understanding experiments, including the possibility of a type of robust zero mode that may emerge without a band-topological transition, called quasi-MBS or non-topological MBS in the field. Finally, I'll discuss the role of spatial non-locality, a special property of MBS wavefunctions that, together with non-Abelian braiding, is the key to realizing topological quantum computation. This work has been recently published as a review in: Nature Reviews Physics 2, 575 (2020)

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

Quantum simulations of condensed matter systems with quantum technologies

Lucas Lamata
Universidad de Sevilla

In this talk I will review recent research on quantum simulations of condensed matter systems with quantum controllable platforms, including trapped ions and superconducting circuits. Among others, we will describe efficient quantum algorithms for simulating fermionic systems in two and three spatial dimensions, as well as proposals for the quantum simulation of the quantum Rabi and Dicke models with analog and digital-analog quantum simulators.

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

Toroids, Active Nematics and Topological Defects

Alberto Fernandez-Nieves
Department of Condensed Matter Physics, University of Barcelona ICREA - Instituci Catalana de Recerca i Estudis Avanats, Barcelona

We will discuss recent results with active nematics confined to either toroidal space. We will first review how we make and stabilize non-spherical droplets and describe how curvature affects defect arrangement on tori. We will show that despite the intrinsic activity and out-of-equilibrium character of the system, there are still remnants of the expected curvature-induced defect unbinding predicted for nematics in their ground state. Activity, however, augments the behavior leading to unexpected defect distributions. We will then focus on defect orientation and show that on flat space, there is short-range orientational correlations without long-range orientational order.

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

Iron-based superconductors Materials, magnetism and tuning methods

Anna Bhmer
Ruhr-University Bochum

Iron-based superconductors represent a second class of high-temperature superconductors after the copper oxides. As they enter their second decade, the large variety of their chemical structures, modes of magnetic ordering and the methods available to tune their properties are all the more appreciated. As with many unconventional superconductors, their magnetic order needs to be suppressed for superconductivity to appear. I will present an overview of the magnetism in several of these iron-based materials and the methods to suppress, or tune, it. Magnetism is particularly strongly coupled to the crystal lattice, which makes structural tuning parameters interesting. I will also discuss some of the other surprising effects that arise from this close interaction of structure, magnetism and superconductivity. Comparing diverse materials and their properties helps us understand some of the common principles within this class of unconventional superconductors.

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

Straintronics with 2D materials

Andrs Castellanos

Strain engineering is an interesting strategy to tune a materials electronic properties by subjecting its lattice to a mechanical deformation. Conventional straining approaches, used for 3D materials (including epitaxial growth on a substrate with a lattice parameter mis-match, the use of a dielectric capping layer or heavy ions implantation) are typically limited to strains lower than 2% in most cases due to the low maximum strains sustained by brittle bulk semiconducting materials. Bulk silicon, for example, can be strained only up to 1.5% before breaking. Moreover, these straining approaches induce static deformations of the semiconductor materials and therefore they are not suitable for tunable functional devices.2D materials can be literally stretched, folded, bent or even pierced. [1] This outstanding stretchability (and the possibility of using dynamically varying strain) of 2D materials promises to revolutionize the field of strain engineering and could lead to "straintronic" devices devices with electronic and optical properties that are engineered through the introduction of mechanical deformations.In this talk I will discuss our recent efforts to study strain engineering in 2D materials and to exploit it to fabricate strain tunable functional optoelectronic devices. [2-7].This project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (grant agreement n 755655, ERC-StG 2017 project 2D-TOPSENSE). ACG acknowledge funding from the EU Graphene Flagship funding (Grant Graphene Core 2, 785219).[1] Roldn et al. Journal of Physics: Condensed Matter (2015) 27 (31), 313201[2] A. Castellanos-Gomez, et al. Nano letters (2013) 13 (11), 5361-5366[3] J. Quereda, et al. Nano letters (2016) 16 (5), 2931-2937[4] J.O. Island, et al. Nanoscale (2016) 8 (5), 2589-2593[5] R. Schmidt et al. 2D Materials (2016) 3 (2), 021011[6] R. Frisenda, et al. npj 2D Materials and Applications (2017) 1 (1), 10[7] P. Gant, et al. Materials Today (2019)

17 de diciembre de 2020, 12:00 h. online

Mechanics of 2D materials

Cristina Gmez-Navarro
IFIMAC, Departamento de Fsica de la Materia Condensada, UAM

IFIMAC+ICMM Joint Seminar Series Condensed Matter @Cantoblanco -- Online event, for abstract and information see https://sites.google.com/view/ifimac-icmm-joint-seminars/home

10 de diciembre de 2020, 12:00 h. online

Twisted layers, narrow bands, and new phases in two dimensional materials

Francisco Guinea
IMDEA Nano & Donostia International Physics Center

IFIMAC+ICMM Joint Seminar Series Condensed Matter @Cantoblanco -- Online event, for abstract and information see https://sites.google.com/view/ifimac-icmm-joint-seminars/home

03 de diciembre de 2020, 12:00 h. online

Manipulating Light and Matter in van der Waals-bonded Semiconductors

Stephane Kena-Cohen
Polytechnique Montral

IFIMAC+ICMM Joint Seminar Series Condensed Matter @Cantoblanco -- Online event, see https://sites.google.com/view/ifimac-icmm-joint-seminars/home


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