21 research outputs found
Preparation, Characterization and electronic structure of Ti-doped BiSe
We report the preparation of high-quality single crystal of BiSe, a
well-known topological insulator and its Ti-doped compositions using Bridgeman
technique. Prepared single crystals were characterized by x-ray diffraction
(XRD) to check the crystalline structure and energy dispersive analysis of
x-rays for composition analysis. The XRD data of Ti-doped compounds show a
small shift with respect to normal BiSe indicating changes in the
lattice parameters while the structure type remained unchanged; this also
establishes that Ti goes to the intended substitution sites. All the above
analysis establishes successful preparation of these crystals with high quality
using Bridgman technique. We carried out x-ray photo-emission spectroscopy to
study the composition via investigating the core level spectra. BiSe
spectra exhibit sharp and distinct features for the core levels and absence of
impurity features. The core level spectra of the Ti-doped sample exhibit
distinct signal due to Ti core levels. The analysis of the spectral features
reveal signature of plasmon excitation and final state satellites; a signature
of finite electron correlation effect in the electronic structure.Comment: Proceedings of DAE SSPS 201
Anomalous spectral evolution with bulk sensitivity in BiPd
We investigate the electronic structure of a noncentrosymmetric
superconductor, BiPd using photoemission spectroscopy with multiple photon
energies ranging from ultraviolet to hard x-ray. Experimental data exhibit
interesting difference in the surface and bulk electronic structures of this
system. While the surface Bi core level peaks appear at lower binding energies,
the surface valence band features are found at the higher binding energy side
of the bulk valence band; valence band is primarily constituted by the Pd 4d
states. These changes in the electronic structure cannot be explained by the
change in ionicity of the constituent elements via charge transfer. Analysis of
the experimental data indicates that the Bi-Pd hybridization physics plays the
key role in deriving the anomalous spectral evolution and the electronic
properties of this system.Comment: Proceedings of DAE SSPS 201
Layer-resolved electronic behavior in a Kondo lattice system, CeAgAs2
We investigate the electronic structure of an antiferromagnetic Kondo lattice
system CeAgAs2 employing hard x-ray photoemission spectroscopy. CeAgAs2, an
orthorhombic variant of HfCuSi2 structure, exhibits antiferromagnetic ground
state, Kondo like resistivity upturn and compensation of magnetic moments at
low temperatures. The photoemission spectra obtained at different photon
energies suggest termination of the cleaved surface at cis-trans-As layers. The
depth-resolved data show significant surface-bulk differences in the As and Ce
core level spectra. The As 2p bulk spectrum shows distinct two peaks
corresponding to two different As layers. The peak at higher binding energy
correspond to cis-trans-As layers and is weakly hybridized with the adjacent Ce
layers. The As layers between Ce and Ag-layers possess close to trivalent
configuration due to strong hybridization with the neighboring atoms and the
corresponding feature appear at lower binding energy. Ce 3d core level spectra
show multiple features reflecting strong Ce-As hybridization and strong
correlation. Intense f0 peak is observed in the surface spectrum while it is
insignificant in the bulk. In addition, we observe a features at binding energy
lower than the well-screened feature indicating the presence of additional
interactions. This feature becomes more intense in the bulk spectra suggesting
it to be a bulk property. Increase in temperature leads to a spectral weight
transfer to higher binding energies in the core level spectra and a depletion
of spectral intensity at the Fermi level as expected in a Kondo material. These
results reveal interesting surface-bulk differences, complex interplay of
intra- and inter-layer covalency, and electron correlation in the electronic
structure of this novel Kondo lattice system
Complexity in the hybridization physics revealed by depth-resolved photoemission spectroscopy of single crystalline novel Kondo lattice systems, CeCuX (X = As/Sb)
We investigate the electronic structure of a novel Kondo lattice system
CeCuX2 (X = As/Sb) employing high resolution depth-resolved photoemission
spectroscopy of high quality single crystalline materials. CeCuSb2 and CeCuAs2
represent different regimes of the Doniach phase diagram exhibiting Kondo-like
transport properties and CeCuSb2 is antiferromagnetic (TN ~ 6.9 K) while
CeCuAs does not show long-range magnetic order down to the lowest
temperature studied. In this study, samples were cleaved in ultrahigh vacuum
before the photoemission measurements and the spectra at different surface
sensitivity establish the pnictogen layer having squarenet structure as the
terminated surface which is weakly bound to the other layers. Cu 2p and As 2p
spectra show spin-orbit split sharp peaks along with features due to plasmon
excitations. Ce 3d spectra exhibit multiple features due to the hybridization
of the Ce 4f/5d states with the valence states. While overall lineshape of the
bulk spectral functions look similar in both the cases, the surface spectra are
very different; the surface-bulk difference is significantly weaker in CeCuAs2
compared to that observed in CeCuSb2. A distinct low binding energy peak is
observed in the Ce 3d spectra akin to the scenario observed in cuprates and
manganites due to the Zhang-Rice singlets and/or high degree of itineracy of
the conduction holes. The valence band spectra of CeCuSb manifest highly
metallic phase. In CeCuAs2, intensity at the Fermi level is significantly small
suggesting a pseudogap-type behavior. These results bring out an interesting
scenario emphasizing the importance and subtlety of hybridization physics
underlying the exoticity of this novel Kondo system
Surface and bulk core level study of PdTe using HAXPES
We report here the preparation of high quality single crystal of PdTe(0001). Various characterizations show good quality of the sample formed in single phase with large sample size suitable for various spectroscopic measurements. We have carried out hard x-ray photoemission spectroscopic (HAXPES) measurements and found interesting results. While Te core level spectrum shows asymmetry as expected in a metallic system, PdTe, the Pd core spectrum does not show such features indicating element selective behavior in the photoemission spectra. We also observe satellites in the core level spectra providing evidence for finite electron correlation induced effect in the electronic structure. Surface and bulk electronic structure is found to be similar in this system
Preparation and electronic structure study of a topological crystalline insulator, SnTe
In this paper, we report preparation and characterization of high quality single crystals of a topological crystalline insulator, SnTe. Samples were prepared using modified Bridgman method and were characterized by powder diffraction, Laue diffraction and energy dispersive x-ray diffraction method. From the resistivity measurements, the temperature for the displacive phase transition is determined to be 40 K. Furthermore, core level photoemission of Sn 3s and Te 3p using photon energy of 5945.24 eV at different temperatures shows that structural transition does not have discernible effect on the studied core level spectra. We observe intense satellite features in the core level spectra suggesting importance of electron correlation in the electronic properties of this syste