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Agenda

Todos

Total 100 eventos
Agenda de eventos
FechaEvento
12/12/2019 - 12/12/2019Superspintronics – towards ultra-low dissipation spin-electronics

 

SPEAKER

Dr Niladri Banerjee

Department of Physics, Loughborough University, United Kingdom.

Abstract:  

The fundamental antagonism between superconductivity and ferromagnetism arises from the nature of electron pairing in these materials - parallel for ferromagnetism and antiparallel (singlet) for superconductivity. However, recent theoretical and experimental evidences [1] suggest a unique form of odd-frequency equal-spin (triplet) superconductivity that arises at carefully engineered interfaces between ferromagnets and superconductors. These equal-spin Cooper pairs are immune to the pair breaking exchange field in a ferromagnet and can propagate over length scales which are significantly longer than the singlet pair coherence lengths. These dissipationless triplet currents carry a net spin which raises the intriguing possibility of ultra-low-dissipation superconducting spin-electronics (superspintronics) [2].

 

In this talk, following a brief introduction, I will discuss recent progress in this area [2-7], specifically focussing on two recent results: spin-orbit coupling-driven superspintronics [5,6] and magnetisation reorientation due to superconducting transition [7].

 

1. J. Linder and J. W. A. Robinson, Nature Physics 11, 307–315 (2015)

2. N. Banerjee, Physics World, Volume 32, Number 4 (2019)

3. N. Banerjee et al., Nature Communications 5:4771 (2014)

4. N. Banerjee et al., Nature Communications 5:3048 (2014)

5. N. Banerjee et al., Phys. Rev. B 97, 184521 (2018)

6. I. Martínez et al. arXiv:1812.08090, (2019)

7. L. G. Johnsen et al., Phys. Rev. B 99, 134516 (2019)

 

 

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

 

 

 

19/06/2019 - 11/10/201925º PREMIO CARMEN Y SEVERO OCHOA DE INVESTIGACIÓN EN BIOLOGÍA MOLECULAR

 

 

 

 

 

 

 

 

 

 

 

07/11/2018 - 07/11/2018Las nuevas Neurotecnologías: impacto en la Ciencia, Medicina y Sociedad

SPEAKER:

DR. Rafael Yuste

Professor of Biological Sciences, Director NeuroTechnology Center, Columbia University, New York.

 

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].

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/

Destacados

No existen eventos destacados en esta categoría

Generales

Total 100 eventos
Agenda de eventos
FechaEvento
12/12/2019 - 12/12/2019Superspintronics – towards ultra-low dissipation spin-electronics

 

SPEAKER

Dr Niladri Banerjee

Department of Physics, Loughborough University, United Kingdom.

Abstract:  

The fundamental antagonism between superconductivity and ferromagnetism arises from the nature of electron pairing in these materials - parallel for ferromagnetism and antiparallel (singlet) for superconductivity. However, recent theoretical and experimental evidences [1] suggest a unique form of odd-frequency equal-spin (triplet) superconductivity that arises at carefully engineered interfaces between ferromagnets and superconductors. These equal-spin Cooper pairs are immune to the pair breaking exchange field in a ferromagnet and can propagate over length scales which are significantly longer than the singlet pair coherence lengths. These dissipationless triplet currents carry a net spin which raises the intriguing possibility of ultra-low-dissipation superconducting spin-electronics (superspintronics) [2].

 

In this talk, following a brief introduction, I will discuss recent progress in this area [2-7], specifically focussing on two recent results: spin-orbit coupling-driven superspintronics [5,6] and magnetisation reorientation due to superconducting transition [7].

 

1. J. Linder and J. W. A. Robinson, Nature Physics 11, 307–315 (2015)

2. N. Banerjee, Physics World, Volume 32, Number 4 (2019)

3. N. Banerjee et al., Nature Communications 5:4771 (2014)

4. N. Banerjee et al., Nature Communications 5:3048 (2014)

5. N. Banerjee et al., Phys. Rev. B 97, 184521 (2018)

6. I. Martínez et al. arXiv:1812.08090, (2019)

7. L. G. Johnsen et al., Phys. Rev. B 99, 134516 (2019)

 

 

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

 

 

 

19/06/2019 - 11/10/201925º PREMIO CARMEN Y SEVERO OCHOA DE INVESTIGACIÓN EN BIOLOGÍA MOLECULAR

 

 

 

 

 

 

 

 

 

 

 

07/11/2018 - 07/11/2018Las nuevas Neurotecnologías: impacto en la Ciencia, Medicina y Sociedad

SPEAKER:

DR. Rafael Yuste

Professor of Biological Sciences, Director NeuroTechnology Center, Columbia University, New York.

 

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].

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/

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La UAM cierra los actos de su 50 Aniversario con la presentación de un documental sobre sus tres décadas de investigación en la Antártida
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  • Universidad Autónoma de Madrid. Enlace externo. Abre en ventana nueva.
  • CSIC. Enlace externo. Abre en ventana nueva.
  • ASEYACOVI. Enlace externo. Abre en ventana nueva.
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  • IIBM - Instituto de Investigaciones Biomédicas Alberto Sols. Enlace externo. Abre en ventana nueva.
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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