Abstract
Understanding the competition between superconductivity and other ordered states (such as antiferromagnetic or charge-density-wave (CDW) state) is a central issue in condensed matter ...physics. The recently discovered layered kagome metal
A
V
3
Sb
5
(
A
= K, Rb, and Cs) provides us a new playground to study the interplay of superconductivity and CDW state by involving nontrivial topology of band structures. Here, we conduct high-pressure electrical transport and magnetic susceptibility measurements to study CsV
3
Sb
5
with the highest
T
c
of 2.7 K in
A
V
3
Sb
5
family. While the CDW transition is monotonically suppressed by pressure, superconductivity is enhanced with increasing pressure up to P1 ≈ 0.7 GPa, then an unexpected suppression on superconductivity happens until pressure around 1.1 GPa, after that,
T
c
is enhanced with increasing pressure again. The CDW is completely suppressed at a critical pressure P2 ≈ 2 GPa together with a maximum
T
c
of about 8 K. In contrast to a common dome-like behavior, the pressure-dependent
T
c
shows an unexpected double-peak behavior. The unusual suppression of
T
c
at P1 is concomitant with the rapidly damping of quantum oscillations, sudden enhancement of the residual resistivity and rapid decrease of magnetoresistance. Our discoveries indicate an unusual competition between superconductivity and CDW state in pressurized kagome lattice.
High pressure electric transport and synchrotron x-ray diffraction (XRD) measurements together with the first-principles calculations are performed on a shandite compound Pd3Pb2Se2 which contains the ...Kagome lattice of the transition metal Pd. A pressure-induced superconducting transition is observed above 25 GPa, for the first time in the shandite compounds, although the crystal structure of the compound seems to be very robust and persists up to the highest pressure in the XRD study (76.3 GPa). The superconducting transition temperature is about 2.2 K and almost does not change with pressure. The carrier density suddenly increases around 20 GPa possibly due to the emergence of two electron pockets at the Γ point. Our work indicates that the superconductivity in Pd3Pb2Se2 is strongly correlated to its electronic structure.
•The bicollinear ground state and the first-order phase transition of iron tellurium are well reproduced.•This work confirms the essential role of the spin–lattice coupling in explaining the magnetic ...properties of iron tellurium.•Specific magnetic excitation in strained iron tellurium is predicted.
In this work, we study the phase diagram of a frustrated Heisenberg model with the additional next nearest neighbor four-spin interaction accounting for the spin–lattice coupling in order to understand the magnetism of iron tellurium. The experimentally identified bicollinear ground state that is always degenerate with the plaquette state in any Heisenberg-biquadratic models Glasbrenner et al., Nat. Phys. 11, 953 (2015) and the first-order phase transition are well reproduced, strongly confirming the essential role of the four-spin interaction related to the spin–lattice coupling Bishop, Moreo, and Dagotto, Phys. Rev. Lett. 117, 117201 (2016) in explaining the magnetic properties of iron tellurium. Moreover, based on the linear spin-wave theory, specific magnetic excitation in strained iron tellurium is predicted, appealing for experimental verification.
This study systematically investigates the interface structure of Nb films grown on MgO substrates with different orientations ((100) and (111)) by experiments and simulations. X-ray diffraction, ...transmission electron microscopy (TEM) and high-resolution TEM (HRTEM) were used to characterize the structure of Nb films and the structure of interfaces between Nb films and MgO substrates. The results show that thin films exhibit different preferred planes on different orientations of MgO substrates. First-principles calculations were used to understand the interface configuration through a coherent interface model. The combination of experiments and simulations shows that the work of separation, together with substrate orientation and lattice mismatch, determines the interface structure between films and substrates.
Summary
In this study, second‐harmonic imaging microscopy was used to monitor precancerous colorectal lesions at different stages. It was found that the morphology of glands and lamina propria in ...mucosa changes with the progression of colorectal diseases from normal to low‐grade intraepithelial neoplasia to high‐grade intraepithelial neoplasia and this microscopy has the ability of direct visualization of these warning symptoms. Furthermore, two morphologic variables were quantified to determine the changes of glands and collagen in lamina propria during the development of colorectal intraepithelial neoplasia. These results suggest that second‐harmonic imaging microscopy has the potential in label‐freely and effectively distinguishing between normal and precancerous colorectal tissues, and will be helpful for early diagnosis and treatment of colorectal diseases.
Lay Description
Colorectal cancer is still a major public health issue in the world, and intraepithelial neoplasia has been widely regarded as a precancerous lesion. Early detection, accurate characterization, and resection of the precursor lesions are essential for the prevention of this malignancy. However, conventional endoscopy examination has limited ability to precisely identify colorectal intraepithelial neoplasia because of limited resolution. Thus, we try to use second‐harmonic imaging microscopy to monitor precancerous colorectal lesions at different stages, and then determine whether this microscopy can identify the pathologic differences between normal and precancerous tissues.
In our study, it was found that the morphology of glands and lamina propria in mucosa changes with the progression of colorectal diseases from normal to low‐grade intraepithelial neoplasia to high‐grade intraepithelial neoplasia and SHG microscopy has the ability of direct visualization of these warning symptoms. Furthermore, two morphologic variables including gland area and pixel density of collagen were quantified to determine the changes of glands and collagen in lamina propria during the development of colorectal intraepithelial neoplasia. These results suggest that second‐harmonic imaging microscopy has the potential in label‐freely and effectively distinguishing between normal and precancerous colorectal tissues, and will be helpful for early diagnosis and treatment of colorectal diseases.
In this paper, the growth mechanism and growth habit of oxide crystals are investigated. Firstly, from the kinetics viewpoint, the growth mechanism of ZnO powders under hydrothermal condition is ...disclosed starting from the hypothesis of growth unit. It is concluded that the growth mechanism of oxide crystals contains the formation of growth units and the incorporation of growth units into the crystal lattice by a dehydration reaction. Then, a new growth interface model of oxide crystals in solution is established on the basis of an ideal growth mechanism of oxide crystals, which considers the interface structure of the crystal as the stacking order of coordination polyhedrons with OH
− ligands. Finally, a new rule concerning the growth habit is deduced considering the relation between the growth rate and the orientation of the coordination polyhedron at the interface. It is concluded that the direction of the crystal face with the corner of the coordination polyhedron occurring at the interface has the fastest growth rate; the direction of the crystal face with the edge of the coordination polyhedron occurring at the interface has the second fastest growth rate; the direction of the crystal face with the face of the coordination polyhedron occurring at the interface has the slowest growth rate. In terms of this rule, the growth habit of ZnO crystal particles and AlO(OH) crystal particles, and the effect of reaction medium on the growth habit are successfully explained.
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