20,775 research outputs found
Generalized effective hamiltonian for graphene under non-uniform strain
We use a symmetry approach to construct a systematic derivative expansion of
the low energy effective Hamiltonian modifying the continuum Dirac description
of graphene in the presence of non-uniform elastic deformations. We extract all
experimentally relevant terms and describe their physical significance. Among
them there is a new gap-opening term that describes the Zeeman coupling of the
elastic pseudomagnetic field and the pseudospin. We determine the value of the
couplings using a generalized tight binding model.Comment: 13 pages, 1 figure. Matches published version + 1 footnote added,
typos correcte
Thermoelectric relations in the conformal limit in Dirac and Weyl semimetals
In the Fermi liquid description of metals, electrical and thermoelectric
transport coefficients are linked by robust relations which can be challenged
by strong interactions or when the electron liquid enters a different regime.
These relations have been very powerful in the characterisation of novel
materials. We show that Dirac and Weyl semimetals at zero doping and zero
temperature (the conformal limit) have a very singular behavior due to a
quantum anomaly. Away from this point, a Mott relation can be established
Visualizing the Doppler Effect
The development of Information and Communication Technologies suggests some
spectacular changes in the methods used for teaching scientific subjects.
Nowadays, the development of software and hardware makes it possible to
simulate processes as close to reality as we want. However, when we are trying
to explain some complex physical processes, it is better to simplify the
problem under study using simplified pictures of the total process by
eliminating some elements that make it difficult to understand this process. In
this work we focus our attention on the Doppler effect which requires the
space-time visualization that is very difficult to obtain using the traditional
teaching resources. We have designed digital simulations as a complement of the
theoretical explanation in order to help students understand this phenomenon.Comment: 16 pages, 8 figure
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