Person:
Díaz Fernández, Álvaro

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First Name
Álvaro
Last Name
Díaz Fernández
URI
https://hdl.handle.net/20.500.14352/86996
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Física de Materiales
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2018 - 20195
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End date: 2019 × Start date: 2018 ×

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Now showing 1 - 5 of 5
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    Project number: 23
    Modernización de contenidos en asignaturas de Física de la Materia Condensada
    (2019) Dominguez-Adame Acosta, Francisco; Díaz García, Elena; Díaz Fernández, Álvaro; Baba, Yuriko Caterina
    El principal objetivo de este Proyecto INNOVA-Docencia es el estudio, análisis y posterior elevación de propuestas para la mejora de la docencia de la Física de la Materia Condensada. Para ello, varios profesores y estudiantes de la Facultad de Ciencias Físicas hemos diseñado, organizado y llevado a cabo las Jornadas Últimos Avances en Física de la Materia Condensada. Se ha elaborado una encuesta para los estudiantes que han participado en las Jornadas. El análisis de los resultados ha permitido elaborar un libro blanco que se ha hecho llegar a los miembros del Departamento de Física de Materiales para su conocimiento y discusión.
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    Reshaping of Dirac Cones in topological insulators and Graphene
    (2019) Díaz Fernández, Álvaro; Domínguez-Adame Acosta, Francisco; Díaz García, Elena
    Quantum mechanics was in all its splendour at the beginning of the twentieth century with the great minds of Schrödinger, Heisenberg, Dirac, Pauli and many others. The concepts introduced by then were truly revolutionary, even more than Einstein’s relativity, one would dare say. One may have a feeling that nowadays we only exploit the consequences of quantum mechanics to build devices such as transistors or light-emitting diodes, which on the other hand have changed the world we live in beyond imagination. With regard to the theoretical front, it may seem that one only has to turn the mathematical handle to work out consequences of quantum mechanics, although no new concepts are in sight. However, nothing could be farther from the truth. We are priviledged to live in what has been dubbed as a second quantum revolution...
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    Project number: 293
    Actualización de material docente basado en Jupyter Notebook para su uso dentro del Plan de Internacionalización
    (2018) Díaz García, Elena; Cabrera Granado, Eduardo; Domínguez-Adame Acosta, Francisco; Gómez Calderón, Óscar; Melle Hernández, Sonia; Díaz Fernández, Álvaro; Villas Pazos, Alberto
    La iniciativa de este proyecto viene justificada a la vista del gran interés generado por algunos de los materiales docentes diseñados por nuestro grupo en anteriores proyectos, en los que se vienen desarrollando diferentes herramientas docentes basadas en el uso de Jupyter Notebooks. A la vista del impacto generado, y teniendo en cuenta que la evolución del proyecto Jupyter, así como las aplicaciones de distintas herramientas asociadas a Jupyter Notebook, es continua, nos planteamos como objetivo principal del presente proyecto la actualización y la puesta a disposición en inglés de nuestra producción de los últimos años.
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    Robust midgap states in band-inverted junctions under electric and magnetic fields
    (Beilstein journal of nanotechnology, 2018) Díaz Fernández, Álvaro; del Valle, Natalia; Domínguez-Adame Acosta, Francisco
    Several IV-VI semiconductor compounds made of heavy atoms, such as Pb1-xSnxTc, may undergo band-inversion at the L point of the Brillouin zone upon variation of their chemical composition. This inversion gives rise to topologically distinct phases, characterized by a change in a topological invariant. In the framework of the k.p theory, band-inversion can be viewed as a change of sign of the fundamental gap. A two-band model within the envelope-function approximation predicts the appearance of midgap interface states with Dirac cone dispersions in band-inverted junctions, namely, when the gap changes sign along the growth direction. We present a thorough study of these interface electron states in the presence of crossed electric and magnetic fields, the electric field being applied along the growth direction of a band-inverted junction. We show that the Dirac cone is robust and persists even if the fields are strong. In addition, we point out that Landau levels of electron states lying in the semiconductor bands can be tailored by the electric field. Tunable devices are thus likely to be realizable, exploiting the properties studied herein.
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    Floquet engineering of Dirac cones on the surface of a topological insulator
    (Physical review B, 2019) Díaz Fernández, Álvaro; Díaz García, Elena; Gómez León, Álvaro; Platero, G.; Domínguez-Adame Acosta, Francisco
    We propose to Floquet engineer Dirac cones at the surface of a three-dimensional topological insulator. We show that a large tunability of the Fermi velocity can be achieved as a function of the polarization, direction, and amplitude of the driving field. Using this external control, the Dirac cones in the quasienergy spectrum may become elliptic or massive, in accordance with experimental evidence. These results help us to understand the interplay of surface states and external ac driving fields in topological insulators. In our work we use the full Hamiltonian for the three-dimensional system instead of effective surface Hamiltonians, which are usually considered in the literature. Our findings show that the Dirac cones in the quasienergy spectrum remain robust even in the presence of bulk states, and therefore, they validate the usage of effective surface Hamiltonians to explore the properties of Floquet-driven topological boundaries. Furthermore, our model allows us to introduce out-of-plane field configurations which cannot be accounted for by effective surface Hamiltonians.