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15/12/2017 - 15/12/2017Geometry invariant phenomena in near zero index media

Abstract:  

Continuous media and metamaterials with a near-zero refractive index (NZI media) provide alternative pathways for the control and manipulation of light-matter 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 geometry-invariant phenomena related to near-zero-index 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 unit-cell 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 - 12/12/2017Charge and energy noise in ac driven conductors

 

Abstract:  

The  time-dependent driving of nanoscale conductors allows for the controlled creation of single-electron excitations. This effect has been demonstrated experimentally both by application of time-dependent driving to gates coupled to confined systems, such as quantum dots [1], and by specifically shaped ac-driving of two-dimensional 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 electron-hole 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 single-particle 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 time-periodic bias voltages, based on a scattering matrix approach [4,5].  Specifically, we investigate the role of electron-like and hole-like excitations created by the driving in the charge current noise, where they only contribute separately. In contrast, additional features due to electron-hole 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 Lorentzian-shaped 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 frequency-dependent temperature and electrochemical-potential fluctuations in a probe reservoir [7].

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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 - 01/12/2017Centrosomes and exosomes molecualr pacemakers of immune synapse

 

 

 

 

 

 

12/09/2017 - 12/09/2017Surface chemical reactions at epitaxial graphene and material beyond graphene

Abstract:  

In this talk, an overview of surface-science 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 time-resolved X-ray photoemission spectroscopy and high-resolution 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 Pt-skin 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 nickel-oxide skin. In the oxidation process, Gr acquires a p-type doping of 0.3 eV [1].

We have also used surface-science tools for investigating Gr employment in the fields of energy and catalysis. By means of a combination of surface-science spectroscopies and density functional theory [2], we have unveiled the mechanisms ruling the catalytic role of epitaxial Gr grown on transition-metal 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 two-dimensional materials provides important information for the nanofabrication process of electronic devices with active channels of ultrathin flakes of black phosphorus (few-layer 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 high-quality single crystals of topological insulators toward ambient gases [6] will be discussed. The subsequent ambient stability of uncapped topological insulator-based nanodevices [7] paves the way for the technological exploitation of topological insulators in the fields of plasmonics [8] and Terahertz photodetection [7].

Finally, surface-science 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 - 30/06/2017Some 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 light-matter interaction will be presented.

 

Marin

 

Más información: http://www.ifimac.uam.es/category/conferences-events

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Generales

Total 100 eventos
Agenda de eventos
FechaEvento
24/05/2018 - 24/05/2018Tunable proximity effect in cuprate superconductor/graphene junctions

Presentación a cargo de David Perconte-Duplain

(Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay)

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 so-called 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.

cid:E16283C1-AF0D-418F-BA2D-F78A1BBB365A

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 24th 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 (5th Floor)

 

SPEAKER: David Perconte-Duplain (Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay)

 

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 so-called 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 - 21/05/2018Resolution of superluminal signalling in non-perturbative cavity quantum electrodynamics

Presentación a cargo de

Carlos Sánchez Muñoz (RIKEN Cluster for Pioneering Research, Wako-shi, 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 single-mode cavity approximation to describe such regimes. We have demonstrated that, in the non-perturbative

light–matter coupling regimes, the single-mode models become unphysical, allowing for superluminal signalling [2]. Moreover, considering the specific example of the quantum Rabi

model, we show that the multi-mode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically

from their single-mode 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 single-mode 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 single-mode 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 multi-mode description is able to capture the spatio-temporal structure of the light field necessary to comply with causality

 

References:

 

[1] Forn-Díaz, 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 21st 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 (5th Floor)

 

SPEAKER: Carlos Sánchez Muñoz (RIKEN Cluster for Pioneering Research, Wako-shi, Japan)

 

TITLE: Resolution of superluminal signalling in non-perturbative 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 single-mode cavity approximation to describe such regimes. We have demonstrated that, in the non-perturbative

light–matter coupling regimes, the single-mode models become unphysical, allowing for superluminal signalling [2]. Moreover, considering the specific example of the quantum Rabi

model, we show that the multi-mode description of the electromagnetic field, necessary to account for light propagation at finite speed, yields physical observables that differ radically

from their single-mode 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 single-mode 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 single-mode 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 multi-mode description is able to capture the spatio-temporal structure of the light field necessary to comply with causality

 

References:

 

[1] Forn-Díaz, 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 - 21/03/2018Spatial Positioning of Innate Controls B Cell Immunity to Infection

Ponente: Mauro Gaya (Ragon Institute of MGH, MIT and Harvard)

08/02/2018 - 08/02/2018Large deviations and quantum non-equilibrium

 

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 - 19/01/2018Interfacing 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 stimuli-responsive 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

 

Macintosh HD:Users:aforment:Documents08:Forment:Proyectos:ERC_Eugenio2017:figures:SCO_GH2.png

 

Más información: http://www.ifimac.uam.es/category/conferences-events

 

 

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Agentes y colaboradores

  • Universidad Autónoma de Madrid
  • CSIC
  • ASEYACOVI
  • ACENOMA
  • AICA
  • Centro de Microanálisis de Materiales (CMAM)
  • Centro de Investigación en Física de la Materia Condensada (IFIMAC)
  • CBMSO - Centro de Biología Molecular Severo Ochoa
  • CIAL - Centro de Investigación en Ciencias de la Alimentación
  • CNB - Centro Nacional de Biotecnología 
  • Centro de Iniciativas Emprendedoras (CIADE)
  • Cámara de Madrid
  • FEMAN
  • Fundación Universitaria Autónoma de Madrid
  • ICMAT - Instituto de Ciencias Matemáticas
  • ICMM - Instituto de Ciencia de Materiales de Madrid
  • ICP - Instituto de Catálisis y Petroquímica
  • ICV - Instituto de Cerámica y Vidrio
  • IFT - Instituto de FísicaTeórica
  • IIBM - Instituto de Investigaciones Biomédicas Alberto Sols
  • IMDEA - Alimentación
  • IMDEA - Nanociencia
  • IMM - Instituto de Microelectrónica de Madrid
  • InNorMadrid
  • Parque Científico de Madrid
  • Oficina de Transferencia de Resultados de la Investigación (OTRI) de la UAM
  • Facultad de Ciencias
  • Facultad de Ciencias Económicas y Empresariales
  • Facultad de Derecho
  • Facultad de Filosofía y Letras
  • Facultad de Medicina
  • Facultad de Formación de Profesorado y Educación
  • Facultad de Psicología
  • Escuela Politécnica Superior
Proyecto realizado con ayudas concedidas por el Ministerio de Economía y Competitividad / EXPEDIENTE: CEI10-1-0009 CEI UAM+CSIC: INNOCAMPUS 2010 Proyecto financiado por el Ministerio de Educación, Cultura y Deporte, y el Ministerio de Economía y Competitividad en el marco del Programa Campus de Excelencia Internacional/ EXPEDIENTE: CEI10-1-0009 CEI UAM+CSIC: INNOCAMPUS 2010