259 research outputs found
Out-of-plane nesting driven spin spiral in ultrathin Fe/Cu(001) films
Epitaxial ultrathin Fe films on fcc Cu(001) exhibit a spin spiral (SS), in
contrast to the ferromagnetism of bulk bcc Fe. We study the in-plane and
out-of-plane Fermi surfaces (FSs) of the SS in 8 monolayer Fe/Cu(001) films
using energy dependent soft x-ray momentum-resolved photoemission spectroscopy.
We show that the SS originates in nested regions confined to out-of-plane FSs,
which are drastically modified compared to in-plane FSs. From precise
reciprocal space maps in successive zones, we obtain the associated real space
compressive strain of 1.5+-0.5% along c-axis. An autocorrelation analysis
quantifies the incommensurate ordering vector q=(2pi/a)(0,0,~0.86), favoring a
SS and consistent with magneto-optic Kerr effect experiments. The results
reveal the importance of in-plane and out-of-plane FS mapping for ultrathin
films.Comment: 4 pages, 3 figure
Temperature-dependent soft x-ray photoemission and absorption studies of charge disproportionation in LaSrFeO
We have measured the temperature dependence of the photoemission and x-ray
absorption spectra of LaSrFeO (LSFO) epitaxial thin films with
, where charge disproportionation () resulting in long-range spin and charge ordering is known to occur
below K. With decreasing temperature we observed gradual changes
of the spectra with spectral weight transfer over a wide energy range of eV. Above the intensity at the Fermi level () was relatively
high compared to that below but still much lower than that in
conventional metals. We also found a similar temperature dependence for
, and to a lesser extent for . These observations suggest that a
local charge disproportionation occurs not only in the sample below
but also over a wider temperature and composition range in LSFO. This
implies that the tendency toward charge disproportionation may be the origin of
the unusually wide insulating region of the LSFO phase diagram.Comment: 6 pages, 8 figure
Layer dependent band dispersion and correlations using tunable Soft X-ray ARPES
Soft X-ray Angle-Resolved Photoemission Spectroscopy is applied to study
in-plane band dispersions of Nickel as a function of probing depth. Photon
energies between 190 and 780 eV were used to effectively probe up to 3-7
layers. The results show layer dependent band dispersion of the Delta_2
minority-spin band which crosses the Fermi level in 3 or more layers, in
contrast to known top 1-2 layers dispersion obtained using ultra-violet rays.
The layer dependence corresponds to an increased value of exchange splitting
and suggests reduced correlation effects in the bulk compared to the surface.Comment: 7 pages, 3 figures Revised text and figur
Collapse of the charge ordering gap of Nd_{0.5}Sr_{0.5}MnO_{3} in an applied magnetic field
We report results of tunneling studies on the charge ordering compound
Nd_{0.5}Sr_{0.5}MnO_{3} in a magnetic field up to 6T and for temperature down
to 25K.We show that a gap (2\Delta_{CO} \approx 0.5eV opens up in the density
of state (DOS) at the Fermilevel (E_F) on charge ordering (T_{CO}=150K) which
collapses in an applied magnetic field when the charge ordered state melts.
There is a clear correspondence between the behavior of the resistivity and the
gap formation and its collapse in an applied magnetic field. We conclude that a
gap in the DOS at E_F is necessary for the stability of the charge ordered
state.Comment: 4 pages REVTeX, 5 postscript figures included, submitted to Phys.
Rev. Let
Three-dimensional bulk band dispersion in polar BiTeI with giant Rashba-type spin splitting
In layered polar semiconductor BiTeI, giant Rashba-type spin-split band
dispersions show up due to the crystal structure asymmetry and the strong
spin-orbit interaction. Here we investigate the 3-dimensional (3D) bulk band
structures of BiTeI using the bulk-sensitive -dependent soft x-ray angle
resolved photoemission spectroscopy (SX-ARPES). The obtained band structure is
shown to be well reproducible by the first-principles calculations, with huge
spin splittings of meV at the conduction-band-minimum and
valence-band-maximum located in the plane. It provides the first
direct experimental evidence of the 3D Rashba-type spin splitting in a bulk
compound.Comment: 9 pages, 4 figure
Revisiting the valence-band and core-level photoemission spectra of NiO
We have re-examined the valence-band (VB) and core-level electronic structure
of NiO by means of hard and soft x-ray photoemission spectroscopy (PES). The
spectral weight of the lowest energy state found to be enhanced in the bulk
sensitive Ni 2p core-level PES. A configuration-interaction model including the
bound state screening has shown significant agreement with the core-level
spectra, and the off and on-resonance VB spectra. These results identify the
lowest energy state in core-level and VB-PES as the Zhang-Rice doublet bound
state, consistent with the spin-fermion model and recent ab initio calculation
with dynamical mean-field theory (LDA + DMFT).Comment: 4 pages, 3 figure
Evidence for mass renormalization in LaNiO$"" sub 3_: an in situ soft x-ray photoemission study of epitaxial films
We investigate the electronic structure of high-quality single-crystal
LaNiO (LNO) thin films using in situ photoemission spectroscopy (PES). The
in situ high-resolution soft x-ray PES measurements on epitaxial thin films
reveal the intrinsic electronic structure of LNO. We find a new sharp feature
in the PES spectra crossing the Fermi level, which is derived from the
correlated Ni 3 electrons. This feature shows significant enhancement
of spectral weight with decreasing temperature. From a detailed analysis of
resistivity data, the enhancement of spectral weight is attributed to
increasing electron correlations due to antiferromagnetic fluctuations.Comment: 4 pages, 4 figures. submitted to Phys. Rev.
- …