Fecha  Evento 

15/12/2017  15/12/2017  Geometry invariant phenomena in near zero index media Abstract: Continuous media and metamaterials with a nearzero refractive index (NZI media) provide alternative pathways for the control and manipulation of lightmatter interactions. The exotic behavior of NZI media is rooted in the fact that the wavelength gets effectively stretched as the refractive index vanishes. This allows for pathological solutions to the wave equation, including spatially static fields distributions which nevertheless dynamically oscillate in time. This paradoxical behavior gives access to a regime of qualitatively different wave dynamics, where the importance of the geometry is lessened, and certain observables are invariant with respect to geometrical deformations, even including changes in the topology of the system.
In this talk, I’ll review and discuss some of the geometryinvariant phenomena related to nearzeroindex media. Examples will include: (i) transmission (tunneling) of waves through deformed waveguides. (ii) Unconventional resonators supporting modes whose eigenfrequency is independent of the geometry of their external boundary. (iii) Violation of effective medium theory geometrical restrictions, enabling, for example, single unitcell metamaterials. (iv) Existence of bound states in open 3D compact resonators with arbitrarily shaped boundaries. Different technological applications and implementations of these concepts will be discussed.
Más información: http://www.ifimac.uam.es/category/seminars/

12/12/2017  12/12/2017  Charge and energy noise in ac driven conductors
Abstract: The timedependent driving of nanoscale conductors allows for the controlled creation of singleelectron excitations. This effect has been demonstrated experimentally both by application of timedependent driving to gates coupled to confined systems, such as quantum dots [1], and by specifically shaped acdriving of twodimensional conductors [2,3]. However, the spectral properties of the injected signal are in general not known; moreover, the particle emission goes along with the excitation of electronhole pairs with some unknown energy distribution. These issues can be addressed by studying fluctuations in the detected currents: not only do such fluctuations provide more insight into how to increase the precision of the singleparticle emission, but also they allow for obtaining more information about the character of the emitted signal.
Here, I will present a theoretical study of charge and energy currents and their fluctuations in coherent conductors driven by different types of timeperiodic bias voltages, based on a scattering matrix approach [4,5]. Specifically, we investigate the role of electronlike and holelike excitations created by the driving in the charge current noise, where they only contribute separately. In contrast, additional features due to electronhole correlations appear in the energy noise. We then compare two different types of driving schemes [6], that is for a driven mesoscopic capacitor [1] as well as for a Lorentzianshaped bias voltage [3], which do not differ in the number of injected particles, but only in their energetic properties. Finally, I will discuss proposals for the detection of charge and energy noise, either through power fluctuations [4], or via frequencydependent temperature and electrochemicalpotential fluctuations in a probe reservoir [7]. References: [1] G. Fève, A. Mahé, J.M. Berroir, T. Kontos, B. Plaçais, D. C. Glattli, A. Cavanna, B. Etienne, Y. Jin: Science 316, 1169 (2007). [2] J. Gabelli and B. Reulet, Phys. Rev. B 87, 075403 (2013). [3] J. Dubois, T. Jullien, F. Portier, P. Roche, A. Cavanna, Y. Jin, W. Wegscheider, P. Roulleau, and D. C. Glattli, Nature 502, 659 (2013). [4] F. Battista, F. Haupt, and J. Splettstoesser, Phys. Rev. B 90, 085418 (2014) [5] F. Battista, F. Haupt, and J. Splettstoesser, J. Phys. Conf. Ser. 568, 052008 (2014) [6] N. Dashti, M. Misiorny, P. Samuelsson, and J. Splettstoesser, in preparation [7] N. Dashti, M. Misiorny, P. Samuelsson, and J. Splettstoesser, in preparation.
Más información: http://www.ifimac.uam.es/category/seminars/ 
01/12/2017  01/12/2017  Centrosomes and exosomes molecualr pacemakers of immune synapse

12/09/2017  12/09/2017  Surface chemical reactions at epitaxial graphene and material beyond graphene Abstract: In this talk, an overview of surfacescience investigations on the chemical reactivity of epitaxial graphene (Gr) and materials “beyond graphene” (van der Waals semiconductors, topological insulators, Dirac semimetals, Weyl semimetals) will be provided.
By means of timeresolved Xray photoemission spectroscopy and highresolution electron energy loss spectroscopy, different surface chemical reactions in epitaxial Gr have been followed in real time (Gr growth by cracking of hydrocarbons, oxidation, intercalation of chemical species). In particular, we have observed that, due to the similar work functions, Gr grows as an undoped sheet on the Ptskin of Pt3Ni(111) but in an oxygen environment Ni segregation toward the surface occurs with selective oxidation of Ni. Subsequently, the Pt skin underneath Gr is replaced by a nickeloxide skin. In the oxidation process, Gr acquires a ptype doping of 0.3 eV [1]. We have also used surfacescience tools for investigating Gr employment in the fields of energy and catalysis. By means of a combination of surfacescience spectroscopies and density functional theory [2], we have unveiled the mechanisms ruling the catalytic role of epitaxial Gr grown on transitionmetal substrates for the production of hydrogen from water. Water decomposition at the Gr/metal interface at room temperature provides a hydrogenated Gr sheet, which is buckled and decoupled from the metal substrate. Molecular hydrogen is released upon heating above T=400 K.
Moreover, the analysis of the chemical reactivity of surface defects of twodimensional materials provides important information for the nanofabrication process of electronic devices with active channels of ultrathin flakes of black phosphorus (fewlayer phosphorene) [3] or InSe [4], which require the use of capping layers in order to avoid surface degradation in ambient conditions. In particular, we find high reactivity of phosphorene toward water, oxygen and CO [5], while water decomposition at room temperature occurs at Se vacancies of InSe [4].
Furthermore, the chemical inertness of highquality single crystals of topological insulators toward ambient gases [6] will be discussed. The subsequent ambient stability of uncapped topological insulatorbased nanodevices [7] paves the way for the technological exploitation of topological insulators in the fields of plasmonics [8] and Terahertz photodetection [7]. Finally, surfacescience investigations on the chemical reactivity of Weyl semimetals and Dirac semimetals, also highlighting their potential applications in catalysis, will be presented. References
[1] A. Politano and G. Chiarello, 2D Mater. 4 (2017) 035003. [2] A. Politano et al., ACS Nano 10 (2016) 4543. [3] L. Viti et al., Adv. Mater. 27 (2015) 5567; L. Viti et al., Adv. Mater. 28 (2016) 7390. [4] A. Politano et al. Nanoscale 8 (2016) 8474. [5 A. Politano et al., Nano Res. 9 (2016) 2598. [6] A. Politano et al., J. Phys. Chem. C 118 (2014) 21517. [7] L. Viti et al., Nano Lett. 16 (2016) 80; A. Politano et al. APL Mater. 5 (2017) 035504. [8] A. Politano et al., Phys. Rev. Lett. 115 (2015) 216802. Más información: http://www.ifimac.uam.es/category/seminars/

30/06/2017  30/06/2017  Some novel science in the field of nanophotonics
Abstract: Via nanophotonics, one can tailor the laws of physics (as far as light is concerned) almost at will. This way, a variety of novel physical phenomena can be enabled and observed. Some examples in topology and lightmatter interaction will be presented.
Más información: http://www.ifimac.uam.es/category/conferencesevents 
Fecha  Evento 

24/05/2018  24/05/2018  Tunable proximity effect in cuprate superconductor/graphene junctions Presentación a cargo de David PerconteDuplain (Unité Mixte de Physique, CNRS, Thales, Univ. ParisSud, Université ParisSaclay) Abstract: Superconductivity induced by proximity effect is particularly interesting in graphene. For example, because of the conduction and valence bands touching at the Dirac point, an unusual form of the Andreev reflection (the socalled specular Andreev reflection) has been predicted theoretically to happen at a superconductor/graphene interface [1]. We have fabricated cuprate superconductor/graphene planar junctions using a combination of lithography, ion irradiation and CVD graphene transfer techniques. The conductance measurements show that the interfaces are transparent such that the electrical transport is governed by Andreev reflection. The devices allow the modulation of graphene doping via either a top or a back gate, and thus enable electrical control of the graphene’s Fermi energy. This allows us to evidence superconducting electron interference effects that constitute an analogue of Klein tunneling for superconducting pairs. The interference effects periodically modulate the conductance across the junction. We perform numerical simulations based on the model developed in [2]. We compare this simulated superconductor graphene interface conductance to the experimental conductance. We will also present recent work on nanometric cuprate superconductor/graphene junctions where we observe conductance oscillations with bias voltage. These oscillation period decrease when increasing the graphene channel length which indicates that the interferences happen inside the graphene channel. References: [1] C. W. J. Beenakker, Phys. Rev. Lett. 97, 067007 (2007) [2] J. Linder, A. Sudbo, Phys. Rev. Lett. 99, 147001 (2007)
Más información: http://www.ifimac.uam.es/category/seminars/
Dear all:
A new IFIMAC Conference will take place on Thursday; May 24^{th} at the Condensed Matter Physics Center (IFIMAC ) You will find all the information below.
WHEN: Thursday; May 24 ^{th} (2018); 12.00 h WHERE: Dpto. Física de la Materia Condensada, Facultad Ciencias, Module 3, Seminar Room (5^{th} Floor)
SPEAKER: David PerconteDuplain (Unité Mixte de Physique, CNRS, Thales, Univ. ParisSud, Université ParisSaclay)
TITLE: Tunable proximity effect in cuprate superconductor/graphene junctions
ABSTRACT: Superconductivity induced by proximity effect is particularly interesting in graphene. For example, because of the conduction and valence bands touching at the Dirac point, an unusual form of the Andreev reflection (the socalled specular Andreev reflection) has been predicted theoretically to happen at a superconductor/graphene interface [1]. We have fabricated cuprate superconductor/graphene planar junctions using a combination of lithography, ion irradiation and CVD graphene transfer techniques. The conductance measurements show that the interfaces are transparent such that the electrical transport is governed by Andreev reflection. The devices allow the modulation of graphene doping via either a top or a back gate, and thus enable electrical control of the graphene’s Fermi energy. This allows us to evidence superconducting electron interference effects that constitute an analogue of Klein tunneling for superconducting pairs. The interference effects periodically modulate the conductance across the junction. We perform numerical simulations based on the model developed in [2]. We compare this simulated superconductor graphene interface conductance to the experimental conductance. We will also present recent work on nanometric cuprate superconductor/graphene junctions where we observe conductance oscillations with bias voltage. These oscillation period decrease when increasing the graphene channel length which indicates that the interferences happen inside the graphene channel. References: [1] C. W. J. Beenakker, Phys. Rev. Lett. 97, 067007 (2007) [2] J. Linder, A. Sudbo, Phys. Rev. Lett. 99, 147001 (2007)
More information: http://www.ifimac.uam.es/category/seminars/ 
21/05/2018  21/05/2018  Resolution of superluminal signalling in nonperturbative cavity quantum electrodynamics Presentación a cargo de Carlos Sánchez Muñoz (RIKEN Cluster for Pioneering Research, Wakoshi, Japan)
Abstract: Recent technological developments have made it increasingly easy to access the nonperturbative regimes of cavity quantum electrodynamics known as ultrastrong or deep strong coupling, where the light–matter coupling becomes comparable to the bare modal frequencies [1]. In this talk, I will discuss the adequacy of the broadly used singlemode cavity approximation to describe such regimes. We have demonstrated that, in the nonperturbative light–matter coupling regimes, the singlemode models become unphysical, allowing for superluminal signalling [2]. Moreover, considering the specific example of the quantum Rabi model, we show that the multimode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically from their singlemode counterparts already for moderate values of the coupling. Our multimode analysis also reveals phenomena of fundamental interest on the dynamics of the intracavity electric field, where a free photonic wavefront and a bound state of virtual photons are shown to coexist. The problem of superluminal signalling in the singlemode Rabi model. a Schematic view of a qubit embedded in a perfect 1D cavity, together with the depiction of the three lowest cavity modes. When the qubit is only coupled to the fundamental mode, the system is described by the Rabi Hamiltonian. b Violation of relativistic causality by the singlemode Rabi model in regimes where g ≈ ωc. An observer placed close to the cavity edge can retrieve information about the initial state of the TLS before light is able to reach its position. c A multimode description is able to capture the spatiotemporal structure of the light field necessary to comply with causality
References:
[1] FornDíaz, P., Lamata, L., Rico, E., Kono, J., & Solano, E. (2018). arXiv:1804.09275. [2] Sánchez Muñoz, C., Nori, F., and De Liberato, S., Nature Communications (2018) 9:1924
Más información: http://www.ifimac.uam.es/category/seminars/
Dear all:
A new IFIMAC Conference will take place on Monday; May 21^{st} at the Condensed Matter Physics Center (IFIMAC ) You will find all the information below.
WHEN: Monday; May 21 st (2018); 12.00 h WHERE: Dpto. Física Teórica de la Materia Condensada, Facultad Ciencias, Module 5, Seminar Room (5^{th} Floor)
SPEAKER: Carlos Sánchez Muñoz (RIKEN Cluster for Pioneering Research, Wakoshi, Japan)
TITLE: Resolution of superluminal signalling in nonperturbative cavity quantum electrodynamics
ABSTRACT: Recent technological developments have made it increasingly easy to access the nonperturbative regimes of cavity quantum electrodynamics known as ultrastrong or deep strong coupling, where the light–matter coupling becomes comparable to the bare modal frequencies [1]. In this talk, I will discuss the adequacy of the broadly used singlemode cavity approximation to describe such regimes. We have demonstrated that, in the nonperturbative light–matter coupling regimes, the singlemode models become unphysical, allowing for superluminal signalling [2]. Moreover, considering the specific example of the quantum Rabi model, we show that the multimode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically from their singlemode counterparts already for moderate values of the coupling. Our multimode analysis also reveals phenomena of fundamental interest on the dynamics of the intracavity electric field, where a free photonic wavefront and a bound state of virtual photons are shown to coexist. The problem of superluminal signalling in the singlemode Rabi model. a Schematic view of a qubit embedded in a perfect 1D cavity, together with the depiction of the three lowest cavity modes. When the qubit is only coupled to the fundamental mode, the system is described by the Rabi Hamiltonian. b Violation of relativistic causality by the singlemode Rabi model in regimes where g ≈ ωc. An observer placed close to the cavity edge can retrieve information about the initial state of the TLS before light is able to reach its position. c A multimode description is able to capture the spatiotemporal structure of the light field necessary to comply with causality
References:
[1] FornDíaz, P., Lamata, L., Rico, E., Kono, J., & Solano, E. (2018). arXiv:1804.09275. [2] Sánchez Muñoz, C., Nori, F., and De Liberato, S., Nature Communications (2018) 9:1924
More information: http://www.ifimac.uam.es/category/seminars/

21/03/2018  21/03/2018  Spatial Positioning of Innate Controls B Cell Immunity to Infection Ponente: Mauro Gaya (Ragon Institute of MGH, MIT and Harvard) 
08/02/2018  08/02/2018  Large deviations and quantum nonequilibrium
Abstract:
I will review recent developments in applying dynamical large deviations (LD) to quantum systems. I will consider in particular open quantum systems  quantum systems interacting with an environment  which in many cases can be described in terms of quantum Markovian dynamics. LD methods provide a "thermodynamic" framework for understanding the statistical properties of dynamics, revealing the existence of dynamical phases and phase transitions, often associated to intermittent emission patterns. Problems of interest include interacting atomic ensembles, quantum glasses, and systems where there is an interplay between coherent transport and dissipation. I will describe concepts relating to quantum trajectory ensemble equivalence, prediction and "retrodiction", matrix product states, and quantum Doob transforms. Time permitting, I will also discuss the connection to ideas about slow quantum relaxation and metastability.
Más información: http://www.ifimac.uam.es/category/seminars/

19/01/2018  19/01/2018  Interfacing magnetic molecules with 2D materials
Abstract: Graphene and other 2D materials have been a hot focus of interest in physics, chemistry and materials science. The emergence of van der Waals heterostructures formed by assembling two different monolayers of these materials through Van der Waals forces have opened new opportunities in this field. This concept can be further expanded by interfacing a layered 2D material with materials of other dimensionalities including 0D materials (molecules, nanoparticles,…), 1D materials (nanotubes, nanowires,…) and 3D materials, which can interact non only through VdW forces but also through covalent or ionic interactions [1]. In this talk I will focus on an emergent class of hybrid heterostructures formed by interfacing a 2D material with a molecular system. In particular, I will show how the properties of the “all surface” 2D material can be tuned through the interactions established with the molecular system. As 2D materials, I will focus on those exhibiting superconductivity or magnetism. As molecular systems, I will focus on stimuliresponsive magnetic molecules able to change their properties upon the application of an external stimulus (temperature, light or pressure) [2]. I will show that this concept can provide examples of smart molecular/2D heterostructures [3], which may be at the origin of a novel generation of hybrid materials and devices of direct application in highly topical fields like electronics, spintronics, molecular sensing and energy storage.
References: [1] D. Jariwala, et al., Nature Mater 2017, 16, 170 [2] A. Bousseksou et al. Chem. Soc. Rev., 2011, 40, 3313. [3] J. Dugay et al. Nano Lett. 2017, 17, 186
Más información: http://www.ifimac.uam.es/category/conferencesevents
 