Fecha  Evento 

14/06/2018  14/06/2018  La Biotecnología en los medios: Cómo nos ve, cómo nos mostramos PONENTES: Margarita del Val, José A. López Guerrero, Elena Campos, Javier Granda

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/ 
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/

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/ 
Fecha  Evento 

14/06/2018  14/06/2018  La Biotecnología en los medios: Cómo nos ve, cómo nos mostramos PONENTES: Margarita del Val, José A. López Guerrero, Elena Campos, Javier Granda

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/ 
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/

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/ 