13 research outputs found
Metamagnetic transitions and anomalous magnetoresistance in EuAgAs single crystal
In this paper, the magnetic and transport properties were systematically
studied for EuAgAs single crystals, crystallizing in a centrosymmetric
trigonal CaCuP type structure. It was confirmed that two magnetic
transitions occur at = 10 K and = 15 K,
respectively. With the increasing field, the two transitions are noticeably
driven to lower temperature. At low temperatures, applying a magnetic field in
the plane induces two successive metamagnetic transitions. For
both and
, EuAgAs shows a positive, unexpected large
magnetoresistance (up to 202\%) at low fields below 10 K, and a large negative
magnetoresistance (up to -78\%) at high fields/intermediate temperatures. Such
anomalous field dependence of magnetoresistance may have potential application
in the future magnetic sensors. Finally, the magnetic phase diagrams of
EuAgAs were constructed for both
and
Drosophila Perlecan Regulates Intestinal Stem Cell Activity via Cell-Matrix Attachment
SummaryStem cells require specialized local microenvironments, termed niches, for normal retention, proliferation, and multipotency. Niches are composed of cells together with their associated extracellular matrix (ECM). Currently, the roles of ECM in regulating niche functions are poorly understood. Here, we demonstrate that Perlecan (Pcan), a highly conserved ECM component, controls intestinal stem cell (ISC) activities and ISC-ECM attachment in Drosophila adult posterior midgut. Loss of Pcan from ISCs, but not other surrounding cells, causes ISCs to detach from underlying ECM, lose their identity, and fail to proliferate. These defects are not a result of a loss of epidermal growth factor receptor (EGFR) or Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling activity but partially depend on integrin signaling activity. We propose that Pcan secreted by ISCs confers niche properties to the adjacent ECM that is required for ISC maintenance of stem cell identity, activity, and anchorage to the niche
Extremely large magnetoresistance in topologically trivial semimetal -WP
Extremely large magnetoresistance (XMR) was recently discovered in many
non-magnetic materials, while its underlying mechanism remains poorly
understood due to the complex electronic structure of these materials. Here, we
report an investigation of the -phase WP, a topologically trivial
semimetal with monoclinic crystal structure (C2/m), which contrasts to the
recently discovered robust type-II Weyl semimetal phase in -WP. We
found that -WP exhibits almost all the characteristics of XMR
materials: the near-quadratic field dependence of MR, a field-induced up-turn
in resistivity following by a plateau at low temperature, which can be
understood by the compensation effect, and high mobility of carriers confirmed
by our Hall effect measurements. It was also found that the normalized MRs
under different magnetic fields has the same temperature dependence in
-WP, the Kohler scaling law can describe the MR data in a wide
temperature range, and there is no obvious change in the anisotropic parameter
value with temperature. The resistance polar diagram has a peanut
shape when field is rotated in plane, which can be understood by
the anisotropy of Fermi surface. These results indicate that both
field-induced-gap and temperature-induced Lifshitz transition are not the
origin of up-turn in resistivity in the -WP semimetal. Our findings
establish -WP as a new reference material for exploring the XMR
phenomena.Comment: 18 pages, 12 figure
Evidence for chiral superconductivity in Kagome superconductor CsV3Sb5
The interplay among frustrated lattice geometry, nontrivial band topology and
correlations yields rich quantum states of matter in Kagome systems. A class of
recent Kagome metals, AV3Sb5 (A= K, Rb, Cs), exhibit a cascade of
symmetry-breaking transitions, involving 3Q chiral charge ordering, electronic
nematicity, roton pair density wave and superconductivity. The interdependence
among multiple competing orders suggests unconventional superconductivity, the
nature of which is yet to be resolved. Here, we report the electronic evidence
for chiral superconducting domains with boundary supercurrent, a smoking-gun of
chiral superconductivity, in intrinsic CsV3Sb5 akes. Magnetic field-free
superconducting diode effects are observed with its polarity modulated by
thermal histories, unveiling a spontaneous time-reversal-symmetry breaking
within dynamical order parameter domains in the superconducting phase.
Strikingly, the critical current exhibits double-slit superconducting
interference patterns, when subjected to external magnetic field. This is
attributed to the periodic modulation of supercurrent owing along chiral domain
boundaries constrained by fluxoid quantization. Our results provide the direct
demonstration of a time-reversal symmetry breaking superconducting order in
Kagome systems, opening a potential for exploring exotic physics, e.g. Majorana
zero modes, in this intriguing topological Kagome system.Comment: 16 pages,13 figure
Clues to potential dipolar-Kondo and RKKY interactions in a polar metal
Abstract The coexistence of electric dipoles and itinerant electrons in a solid was postulated decades ago, before being experimentally established in several ‘polar metals’ during the last decade. Here, we report a concentration-driven polar-to-nonpolar phase transition in electron-doped BaTiO3. Comparing our case with other polar metals, we find a particular threshold concentration (n *) linked to the dipole density (n d). The universal ratio n d n * ≈ 8.0 ( 6 ) suggests a common mechanism across different polar systems, possibly explained by a dipolar Ruderman-Kittel-Kasuya-Yosida theory. Moreover, in BaTiO3, we observe enhanced thermopower and upturn on resistivity at low temperatures near n *, resembling the Kondo effect. We argue that local electric dipoles act as two-level-systems, whose fluctuations couple with surrounding electron clouds, giving rise to a potential dipolar-counterpart of the Kondo effect. Our findings unveil a mostly uncharted territory for exploring emerging physics associated with electron-dipole correlations, encouraging further theoretical work on dipolar-RKKY and Kondo interactions
Thermoelectric Properties of <i>n</i>-Type Bi<sub>4</sub>O<sub>4</sub>SeX<sub>2</sub> (X = Cl, Br)
The multiple anion superlattice Bi4O4SeCl2 has been reported to exhibit extremely low thermal conductivity along the stacking c-axis, making it a promising material for thermoelectric applications. In this study, we investigate the thermoelectric properties of Bi4O4SeX2 (X = Cl, Br) polycrystalline ceramics with different electron concentrations by adjusting the stoichiometry. Despite optimizing the electric transport, the thermal conductivity remained ultra-low and approached the Ioffe–Regel limit at high temperatures. Notably, our findings demonstrate that non-stoichiometric tuning is a promising approach for enhancing the thermoelectric performance of Bi4O4SeX2 by refining its electric transport, resulting in a figure of merit of up to 0.16 at 770 K
Commensurate Stacking Phase Transitions in an Intercalated Transition Metal Dichalcogenide
Intercalation and stacking-order modulation are two active ways in manipulating the interlayer interaction of transition metal dichalcogenides (TMDCs), which lead to a variety of emergent phases and allow for engineering material properties. Herein, the growth of Pb-intercalated TMDCs–Pb(TaSe), the first 124-phase, is reported. Pb(TaSe) exhibits a unique two-step first-order structural phase transition at around 230 K. The transitions are solely associated with the stacking degree of freedom, evolving from a high-temperature (high-T) phase with ABC stacking and R3m symmetry to an intermediate phase with AB stacking and P3m1, and finally to a low-temperature (low-T) phase again with Rmsymmetry, but with ACB stacking. Each step involves a rigid slide of building blocks by a vector [1/3, 2/3, 0]. Intriguingly, gigantic lattice contractions occur at the transitions on warming. At low-T, bulk superconductivity with Tc ≈ 1.8 K is observed. The underlying physics of the structural phase transitions are discussed from first-principle calculations. The symmetry analysis reveals topological nodal lines in the band structure. The results demonstrate the possibility of realizing higher-order metal-intercalated phases of TMDCs and advance the knowledge of polymorphic transitions, and may inspire stacking-order engineering in TMDCs and beyond