16 research outputs found
Imaging Josephson Vortices on Curved Junctions
Understanding the nature of vortices in type-II superconductors has been
vital for deepening the physics of exotic superconductors and applying
superconducting materials to future electronic devices. A recent study has
shown that the LiTi2O4(111) thin film offers a unique experimental platform to
unveil the nature of the vortex along the curved Josephson junction. This study
successfully visualized individual Josephson vortices along the curved
Josephson junctions using in-situ spectroscopic scanning tunneling microscopy
on LiTi2O4 (111) epitaxial thin films. Notably, the local curvature of the
Josephson junction was discovered to control the position of Josephson
vortices. Furthermore, the numerical simulation reproduces the critical role of
the curvature of the Josephson junction. This study provides guidelines to
control Josephson vortices through geometrical ways, such as mechanical
controlling of superconducting materials and their devices
Evolution of the Fe-3 impurity band state as the origin of high Curie temperature in p-type ferromagnetic semiconductor (Ga,Fe)Sb
(Ga,Fe)Sb is one of the promising ferromagnetic semiconductors
for spintronic device applications because its Curie temperature ()
is above 300 K when the Fe concentration is equal to or higher than ~0.20.
However, the origin of the high in (Ga,Fe)Sb remains to be
elucidated. To address this issue, we use resonant photoemission spectroscopy
(RPES) and first-principles calculations to investigate the dependence of
the Fe 3 states in (Ga,Fe)Sb ( = 0.05, 0.15, and 0.25) thin
films. The observed Fe 2-3 RPES spectra reveal that the Fe-3 impurity
band (IB) crossing the Fermi level becomes broader with increasing , which
is qualitatively consistent with the picture of double-exchange interaction.
Comparison between the obtained Fe-3 partial density of states and the
first-principles calculations suggests that the Fe-3 IB originates from the
minority-spin () states. The results indicate that enhancement
of the interaction between electrons with increasing is the
origin of the high in (Ga,Fe)Sb
Three-dimensional electronic structure in ferromagnetic with breathing kagome bilayers
A large anomalous Hall effect (AHE) has been observed in ferromagnetic
with breathing kagome bilayers. To understand the
underlying mechanism for this, we investigate the electronic structure of
by angle-resolved photoemission spectroscopy
(ARPES). In particular, we use both vacuum ultraviolet light (VUV) and soft x
ray (SX), which allow surface-sensitive and relatively bulk-sensitive
measurements, respectively, and distinguish bulk states from surface states,
which should be unlikely related to the AHE. While VUV-ARPES observes
two-dimensional bands mostly due to surface states, SX-ARPES reveals
three-dimensional band dispersions with a periodicity of the rhombohedral unit
cell in the bulk. Our data show a good consistency with a theoretical
calculation based on density functional theory, suggesting a possibility that
is a magnetic Weyl semimetal.Comment: 6 pages, 4 figure
遷移金属ダイカルコゲナイドの表面および電子状態への元素置換効果の研究
東京理科大学201
Single Crystal Growth and Superconducting Properties of Antimony-Substituted NdO0.7F0.3BiS2
Antimony (Sb) substitution of less than 8% was examined on a single crystal of a layered superconductor NdO0.7F0.3BiS2. The superconducting transition temperature of the substituted samples decreased as Sb concentration increased. A lattice constant along the c-axis showed a large decrease compared with that along the a-axis. Since in-plane chemical pressure monotonically decreased as Sb concentration increased, the suppression of the superconductivity is attributed to the decrease in the in-plane chemical pressure
Large antiferromagnetic fluctuation enhancement of the thermopower at a critical doping in magnetic semimetal Cr1+δTe2
Cr 1+ δ Te 2 is a self-intercalated transition metal dichalcogenide that hosts tunable electronic filling and magnetism in its semimetallic band structure. Recent angle-resolved photoemission spectroscopy (ARPES) studies have unveiled a systematic shift in this semimetallic band structure relative to the chemical potential with increased Cr doping. This report presents the temperature and magnetic field dependence of the longitudinal thermopower S xx for different Cr 1+ δ Te 2 compositions. We show that as doping increases, the sign of S xx changes from positive to negative at the critical doping level of δ ~ 0.5. This observed doping-dependent trend in the thermopower is consistent with the evolution of the semimetallic band structure from ARPES. Importantly, an anomalous enhancement of the thermoelectric response near T C is also observed around δ ~ 0.5. Combining information from magnetometry and ARPES measurements, existence of the critical nature of the doping level δ c (~ 0.5) is unveiled in magnetic semimetal Cr 1+ δ Te 2 , where antiferromagnetic fluctuation and near-Fermi-energy pseudogap formation play a potential vital role in enhancing thermoelectric energy conversion