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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/

 

14/12/2017 - 14/12/2017Polariton lattices a novel platform for analogue simulation

 

Abstract:  

A large variety of computationally intractable systems can be mapped into certain univer-

sal classical spin models such as an Ising, X Y or Heisenberg models that are characterised by given degrees of freedom, “spins”, their interactions, “couplings,” and their associated cost function, “Hamiltonian”.  Various physical platforms have been proposed to simulate such models using superconducting  qubits, optical lattices, coupled lasers etc.

We  introduce polariton  lattices as a  new platform  for  analogue  simula- tion;   based on well-established semi- conductor and optical control technolo- gies polariton simulators allow for rapid scalability,  ease  of tunability  and ef- fortless readability.   Polariton conden- sates can be  imprinted  into  any two- dimensional lattices either  by  spatial modulation  of  the  pumping  laser or by lithographic techniques during the growth process, offering straightforward scalability.    In  the  case  of  optically imprinted polariton lattices with freely propagating polariton condensates,  we recently demonstrated that  the phase- configuration acquired in  a  polariton dyad or triad  is chosen  so as to max- imise polariton occupancy [1], while by expanding to square, and rhombic lat- tices as  well as  to arbitrary  polariton graphs we  simulated annealing of the X Y Hamiltonian through bosonic stim- ulation [2]. The bottom-up approach of

bosonic stimulation is achieved here by gradually increasing the excitation density to con- densation threshold. This is an advantage over classical or quantum annealing techniques, where the global ground state is reached through transitions over metastable excited states with an increase of the cost of the search with the size of the system.

By controlling the separation distance, in-plane wavevector, and spin of the injected condensates in polariton graphs, we acquire  several degrees of freedom in the tunability of  inter-site interactions, whilst the continuous coupling of polaritons to free photons offers effortless readability of all the characteristics of the polariton condensates such as energy, momentum, spin, and most critically their phase. The above constitute a unique toolbox for realising intriguing discrete giant vortices, controllable next nearest neighbour interactions, dynamic phase transitions and simulating artificial solids.

References:

 

[1] H. Ohadi, R.L. Gregory, T. Freegarde, Y.G. Rubo, A.V. Kavokin, N.G. Berloff, and

P.G. Lagoudakis, Phys. Rev. X, 6, 031032 (2016)

[2] Natalia G. Berloff, Matteo Silva, Kirill  Kalinin, Alexis Askitopoulos, Julian D. T¨opfer, Pasquale Cilibrizzi, Wolfgang Langbein and Pavlos G. Lagoudakis, Nature Materials in

print DOI: 10.1038/NMAT4971 (2017)

 

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].

sys

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

 

 

 

 

 

 

15/11/2017 - 15/11/2017Pair correlation function of a 2D molecular gas directly visualized by scanning tunneling microscopy

 

Abstract:  

The state of matter in fluid phases, determined by the interactions between particles, can be characterized by a pair correlation function (PCF). At the nanoscale, the PCF has been so far obtained experimentally only by means of reciprocal-space techniques. We use scanning tunneling microscopy (STM) at room temperature in combination with lattice-gas kinetic Monte Carlo (KMC) simulations to study a two-dimensional gas of highly mobile molecules of fluorinated copper phthalocyanine on a Si(111)/Tl-(1×1) surface. A relatively slow mechanism of STM image acquisition results in time-averaging of molecular occurrence under the STM tip. We prove by the KMC simulations that in the proximity of fixed molecules STM images represent the PCF. We demonstrate that STM is capable of visualizing directly the pair correlation function in real space.

 

Más información: http://www.ifimac.uam.es/category/seminars/

 

Destacados

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Generales

Total 100 eventos
Agenda de eventos
FechaEvento
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/

 

14/12/2017 - 14/12/2017Polariton lattices a novel platform for analogue simulation

 

Abstract:  

A large variety of computationally intractable systems can be mapped into certain univer-

sal classical spin models such as an Ising, X Y or Heisenberg models that are characterised by given degrees of freedom, “spins”, their interactions, “couplings,” and their associated cost function, “Hamiltonian”.  Various physical platforms have been proposed to simulate such models using superconducting  qubits, optical lattices, coupled lasers etc.

We  introduce polariton  lattices as a  new platform  for  analogue  simula- tion;   based on well-established semi- conductor and optical control technolo- gies polariton simulators allow for rapid scalability,  ease  of tunability  and ef- fortless readability.   Polariton conden- sates can be  imprinted  into  any two- dimensional lattices either  by  spatial modulation  of  the  pumping  laser or by lithographic techniques during the growth process, offering straightforward scalability.    In  the  case  of  optically imprinted polariton lattices with freely propagating polariton condensates,  we recently demonstrated that  the phase- configuration acquired in  a  polariton dyad or triad  is chosen  so as to max- imise polariton occupancy [1], while by expanding to square, and rhombic lat- tices as  well as  to arbitrary  polariton graphs we  simulated annealing of the X Y Hamiltonian through bosonic stim- ulation [2]. The bottom-up approach of

bosonic stimulation is achieved here by gradually increasing the excitation density to con- densation threshold. This is an advantage over classical or quantum annealing techniques, where the global ground state is reached through transitions over metastable excited states with an increase of the cost of the search with the size of the system.

By controlling the separation distance, in-plane wavevector, and spin of the injected condensates in polariton graphs, we acquire  several degrees of freedom in the tunability of  inter-site interactions, whilst the continuous coupling of polaritons to free photons offers effortless readability of all the characteristics of the polariton condensates such as energy, momentum, spin, and most critically their phase. The above constitute a unique toolbox for realising intriguing discrete giant vortices, controllable next nearest neighbour interactions, dynamic phase transitions and simulating artificial solids.

References:

 

[1] H. Ohadi, R.L. Gregory, T. Freegarde, Y.G. Rubo, A.V. Kavokin, N.G. Berloff, and

P.G. Lagoudakis, Phys. Rev. X, 6, 031032 (2016)

[2] Natalia G. Berloff, Matteo Silva, Kirill  Kalinin, Alexis Askitopoulos, Julian D. T¨opfer, Pasquale Cilibrizzi, Wolfgang Langbein and Pavlos G. Lagoudakis, Nature Materials in

print DOI: 10.1038/NMAT4971 (2017)

 

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].

sys

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

 

 

 

 

 

 

15/11/2017 - 15/11/2017Pair correlation function of a 2D molecular gas directly visualized by scanning tunneling microscopy

 

Abstract:  

The state of matter in fluid phases, determined by the interactions between particles, can be characterized by a pair correlation function (PCF). At the nanoscale, the PCF has been so far obtained experimentally only by means of reciprocal-space techniques. We use scanning tunneling microscopy (STM) at room temperature in combination with lattice-gas kinetic Monte Carlo (KMC) simulations to study a two-dimensional gas of highly mobile molecules of fluorinated copper phthalocyanine on a Si(111)/Tl-(1×1) surface. A relatively slow mechanism of STM image acquisition results in time-averaging of molecular occurrence under the STM tip. We prove by the KMC simulations that in the proximity of fixed molecules STM images represent the PCF. We demonstrate that STM is capable of visualizing directly the pair correlation function in real space.

 

Más información: http://www.ifimac.uam.es/category/seminars/

 

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#InnoAlimentación: La nutrición del futuro. Tecnologías, tendencias y networking
El profesor Jeff Errington imparte la 12ª Lección Conmemorativa David Vázquez
XXIV Lección Conmemorativa en honor de Severo Ochoa, a cargo del Profesor Fred Gage

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