849 research outputs found
Field-induced phase transition in the periodic Anderson model
We investigate the effect of magnetic fields on a Kondo insulator by using
the periodic Anderson model. The analysis by dynamical mean field theory
combined with quantum Monte Carlo simulations reveals that the magnetic field
drives the Kondo insulator to a transverse antiferromagnetic insulator at low
temperatures. We calculate the staggered spin susceptibility and find its
divergence signaling the antiferromagnetic instability. Further investigation
of the spin correlation functions and the magnetization process clarifies how
the magnetic field suppresses the Kondo singlet formation and induces the
transverse antiferromagnetic ordering.Comment: 2 pages, 2 figures, submitted to SCES200
Field induced phase transition in the few photon regime
Some features of the field induced phase transition accompanied by the vacuum
creation of an electron-positron plasma (EPP) in strong time-dependent electric
fields have been discussed in the work [1] in the domain of the tunneling
mechanism (, where is the characteristic frequency of
the external field and is the electron mass). In the present contribution
the features of the this process will be considered in the few photon domain
where . We observe a narrowing of the transient domain of the
fast oscillations and, mainly, a considerable growth of the effectiveness of
the EPP production. Under these circumstances, we see an increase of the
effectiveness of the EPP creation in the particular case of a bifrequent
excitation, where both mechanisms (tunneling and few photon) act simultaneously
[2,3].Comment: 6 pages, 4 figures, contribution to the Proceedings of the XXIII
International Baldin Seminar on "High Energy Physics Problems", Dubna,
Russia, September 19-24, 201
Correlation between electric-field-induced phase transition and piezoelectricity in lead zirconate titanate films
We observed that electric field induces phase transition from tetragonal to
rhombohedral in polycrystalline morphotropic lead zirconate titanate (PZT)
films, as reported in 2011 for bulk PZT. Moreover, we evidenced that this
field-induced phase transition is strongly correlated with PZT film
piezoelectric properties, that is to say the larger the phase transition, the
larger the longitudinal piezoelectric coefficient d 33,eff . Although d 33,eff
is already comprised between as 150 to 170 pm/V, our observation suggests that
one could obtain larger d 33,eff values, namely 250 pm/V, by optimizing the
field-induced phase transition thanks to composition fine tuning
Excitonic instability and electric-field-induced phase transition towards a two dimensional exciton condensate
We present an InAs-GaSb-based system in which the electric-field tunability
of its 2D energy gap implies a transition towards a thermodynamically stable
excitonic condensed phase. Detailed calculations show a 3 meV BCS-like gap
appearing in a second-order phase transition with electric field. We find this
transition to be very sharp, solely due to exchange interaction, and so, the
exciton binding energy is greatly renormalized even at small condensate
densities. This density gradually increases with external field, thus enabling
the direct probe of the Bose-Einstein to BCS crossover.Comment: LaTex, 11 pages, 3 ps figures, To appear in PR
Thermodynamical Study on the Heavy-Fermion Superconductor PrOs4Sb12: Evidence for Field-Induced Phase Transition
We report measurements of low-temperature specific heat on the 4f^2-based
heavy-fermion superconductor PrOs4Sb12. In magnetic fields above 4.5 T in the
normal state, distinct anomalies are found which demonstrate the existence of a
field-induced ordered phase (FIOP). The Pr nuclear specific heat indicates an
enhancement of the 4f magnetic moment in the FIOP. Utilizing a Maxwell
relation, we conclude that anomalous entropy, which is expected for a
single-site quadrupole Kondo model, is not concealed below 0.16 K in zero
field. We also discuss two possible interpretations of the Schottky-like
anomaly at ~3 K, i.e., a crystalline-field excitation or a hybridization gap
formation.Comment: 5 pages with 5 figures, a note with two references added in proo
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