295 research outputs found
Spin-wave coupling to electromagnetic cavity fields in dysposium ferrite
Coupling of spin-waves with electromagnetic cavity field is demonstrated in
an antiferromagnet, dysprosium ferrite (DyFeO3). By measuring transmission at
0.2-0.35 THz and sweeping sample temperature, magnon-photon coupling signatures
were found at crossings of spin-wave resonances with Fabry-Perot cavity modes
formed in samples. The obtained spectra are explained in terms of classical
electrodynamics and a microscopic model.Comment: 3 pages, 2 figure
Ultrafast Optical Control of the Electronic Properties of
We report on the temperature dependence of the electronic
properties, studied at equilibrium and out of equilibrium, by means of time and
angle resolved photoelectron spectroscopy. Our results unveil the dependence of
the electronic band structure across the Fermi energy on the sample
temperature. This finding is regarded as the dominant mechanism responsible for
the anomalous resistivity observed at T* 160 K along with the change of
the charge carrier character from holelike to electronlike. Having addressed
these long-lasting questions, we prove the possibility to control, at the
ultrashort time scale, both the binding energy and the quasiparticle lifetime
of the valence band. These experimental evidences pave the way for optically
controlling the thermoelectric and magnetoelectric transport properties of
Synthesis of Homogeneous Manganese-Doped Titanium Oxide Nanotubes from Titanate Precursors
We report a novel synthesis route of homogeneously manganese-doped titanium
dioxide nanotubes in a broad concentration range. The scroll-type trititanate
(H(2)Ti(3)O(7)) nanotubes prepared by hydrothermal synthesis were used as
precursors. Mn2+ ions were introduced by an ion exchange method resulting
Mn(x)H(2-x)Ti(3)O(7). In a subsequent heat-treatment they were transformed into
Mn(y)Ti(1-y)O(2) where y=x/(3+x). The state and the local environment of the
Mn2+ ions in the precursor and final products were studied by Electron Spin
Resonance (ESR) technique. It was found that the Mn2+ ions occupy two
positions: the first having an almost perfect cubic symmetry while the other is
in a strongly distorted octahedral site. The ratio of the two Mn2+ sites is
independent of the doping level and amounts to 15:85 in Mn(x)H(2-x)Ti(3)O(7)
and to 5:95 in Mn(y)Ti(1-y)O(2). SQUID magnetometry does not show long-range
magnetic order in the homogeneously Mn2+-doped nanotubes.Comment: 7 pages, 6 figure
Revealing the role of electrons and phonons in the ultrafast recovery of charge density wave correlations in 1-TiSe
Using time- and angle-resolved photoemission spectroscopy with selective
near- and mid-infrared photon excitations, we investigate the femtosecond
dynamics of the charge density wave (CDW) phase in 1-TiSe, as well as
the dynamics of CDW fluctuations at 240 K. In the CDW phase, we observe the
coherent oscillation of the CDW amplitude mode. At 240 K, we single out an
ultrafast component in the recovery of the CDW correlations, which we explain
as the manifestation of electron-hole correlations. Our momentum-resolved study
of femtosecond electron dynamics supports a mechanism for the CDW phase
resulting from the cooperation between the interband Coulomb interaction, the
mechanism of excitonic insulator phase formation, and electron-phonon coupling.Comment: 9 pages, 6 figure
BiTeCl and BiTeBr: a comparative high-pressure optical study
We here report a detailed high-pressure infrared transmission study of BiTeCl
and BiTeBr. We follow the evolution of two band transitions: the optical
excitation between two Rashba-split conduction bands, and the
absorption across the band gap. In the low pressure range, ~GPa,
for both compounds is approximately constant with pressure and
decreases, in agreement with band structure calculations. In BiTeCl, a clear
pressure-induced phase transition at 6~GPa leads to a different ground state.
For BiTeBr, the pressure evolution is more subtle, and we discuss the
possibility of closing and reopening of the band gap. Our data is consistent
with a Weyl phase in BiTeBr at 56~GPa, followed by the onset of a structural
phase transition at 7~GPa.Comment: are welcom
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