52 research outputs found
In situ crystal growth of zeolitic imidazolate frameworks (ZIF) on electrospun polyurethane nanofibers
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.This paper reports for the first time in situcrystal growth of ZIF-8 on electrospun polyurethane (PU) nanofibers. In SEM images, continuous and compact ZIF-8 nanocrystals grow along electrospun PU nanofibers. The highest loading capacity of ZIF-8 on PU reaches 63%. By N2adsorption–desorption, ZIF-8-PU shows a high surface area of 566 cm2g−1. Combining the good flexibility of PU with the high adsorption properties of ZIF-8, ZIF-8-PU can be easily tailored into clothes or other forms as adsorption material. Furthermore, the gas adsorption ability of ZIF-8-PU was measured for H2, N2, O2and CO2at room temperature (20 °C) under different pressure gradients. The results show that the adsorption capacity of ZIF-8-PU for CO2is nearly 11 times that for H2, 50 times that for O2and 75 times that for N2at 800 mmHg
Tomonaga Luttinger liquid in the topological edge channel of multilayer FeSe
A two dimensional topological insulator exhibits helical edge states
topologically protected against single particle backscattering. Such protection
breaks down, however, when electron electron interactions are significant or
when edge reconstruction occurs, leading to suppressed density of states (DOS)
at Fermi level that follows universal scaling with temperature and energy,
characteristic of Tomonaga Luttinger liquid (TLL). Here, we grow multilayer
FeSe on SrTiO3 by molecular beam epitaxy, and observe robust edge states at
both {100}Se and {110}Se steps using scanning tunneling
microscopy/spectroscopy. We determine the DOS follows a power law, resulting in
Luttinger parameter K of 0.26 +/- 0.02 and 0.43 +/- 0.07 for {100}Se and
{110}Se edges, respectively. The smaller K for the {100}Se edge also indicates
strong correlations, attributed to ferromagnetic ordering likely present due to
checkerboard antiferromagnetic fluctuations in FeSe. These results demonstrate
TLL in FeSe helical edge channels, providing an exciting model system for novel
topological excitations arising from superconductivity and interacting helical
edge states.Comment: 28 page
Giant periodic pseudo-magnetic fields in strained kagome magnet FeSn epitaxial films on SrTiO(111) substrate
Quantum materials, particularly Dirac materials with linearly dispersing
bands, can be effectively tuned by strain-induced lattice distortions leading
to a pseudo-magnetic field that strongly modulates their electronic properties.
Here, we grow kagome magnet FeSn films, consisting of alternatingly stacked
Sn honeycomb (stanene) and FeSn kagome layers, on SrTiO(111)
substrates by molecular beam epitaxy. Using scanning tunneling
microscopy/spectroscopy, we show that the Sn honeycomb layer can be
periodically deformed by epitaxial strain for film thickness below 10 nm,
resulting in differential conductance peaks consistent with Landau levels
generated by a pseudo-magnetic field greater than 1000 T. Our findings
demonstrate the feasibility of strain engineering the electronic properties of
topological magnets at the nanoscale.Comment: 46 page
Visualizing symmetry-breaking electronic orders in epitaxial Kagome magnet FeSn films
Kagome lattice hosts a plethora of quantum states arising from the interplay
of topology, spin-orbit coupling, and electron correlations. Here, we report
symmetry-breaking electronic orders tunable by an applied magnetic field in a
model Kagome magnet FeSn consisting of alternating stacks of two-dimensional
Fe3Sn Kagome and Sn2 honeycomb layers. On the Fe3Sn layer terminated FeSn thin
films epitaxially grown on SrTiO3(111) substrates, we observe trimerization of
the Kagome lattice using scanning tunneling microscopy/spectroscopy, breaking
its six-fold rotational symmetry while preserving the transitional symmetry.
Such a trimerized Kagome lattice shows an energy-dependent contrast reversal in
dI/dV maps, which is significantly enhanced by bound states induced by Sn
vacancy defects. This trimerized Kagome lattice also exhibits stripe
modulations that are energy-dependent and tunable by an applied in-plane
magnetic field, indicating symmetry-breaking nematicity from the entangled
magnetic and charge degrees of freedom in antiferromagnet FeSn
Tuning quantum paramagnetism and d-wave superconductivity in single-layer iron chalcogenides by chemical pressure
By substituting S into single-layer FeSe/SrTiO3, chemical pressure is applied
to tune its paramagnetic state that is modeled as an incoherent superposition
of spin-spiral states. The resulting electronic bands resemble an ordered
checkerboard antiferromagnetic structure, consistent with angle-resolved
photoemission spectroscopy measurements. Scanning tunneling spectroscopy
reveals a gap evolving from U-shaped for FeSe to V-shaped for FeS with
decreasing size, attributed to a d-wave superconducting state for which nodes
emerge once the gap size is smaller than the effective spin-orbit coupling
Development and Characterization of Nb₃n/Al₂0₃ Superconducting Multilayers for Particle Accelerators
Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors \u3e 1010 at 1-2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200-240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb3Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration field in Nb3Sn, it has been proposed to coat Nb cavities with thin film Nb3Sn multilayers with dielectric interlayers. Here, we report the growth and multi-technique characterization of stoichiometric Nb3Sn/Al2O3 multilayers with good superconducting and RF properties. We developed an adsorption-controlled growth process by co-sputtering Nb and Sn at high temperatures with a high overpressure of Sn. The cross-sectional scanning electron transmission microscope images show no interdiffusion between Al2O3 and Nb3Sn. Low-field RF measurements suggest that our multilayers have quality factor comparable with cavity-grade Nb at 4.2 K. These results provide a materials platform for the development and optimization of high-performance SIS multilayers which could overcome the intrinsic limits of the Nb cavity technology
A microRNA/Runx1/Runx2 network regulates prostate tumor progression from onset to adenocarcinoma in TRAMP mice
While decades of research have identified molecular pathways inducing and promoting stages of prostate cancer malignancy, studies addressing dynamic changes of cancer-related regulatory factors in a prostate tumor progression model are limited. Using the TRAMP mouse model of human prostate cancer, we address mechanisms of deregulation for the cancer-associated transcription factors, Runx1 and Runx2 by identifying microRNAs with reciprocal expression changes at six time points during 33 weeks of tumorigenesis. We molecularly define transition stages from PIN lesions to hyperplasia/neoplasia and progression to adenocarcinoma by temporal changes in expression of human prostate cancer markers, including the androgen receptor and tumor suppressors, Nkx3.1 and PTEN. Concomitant activation of PTEN, AR, and Runx factors occurs at early stages. At late stages, PTEN and AR are downregulated, while Runx1 and Runx2 remain elevated. Loss of Runx-targeting microRNAs, miR-23b-5p, miR-139-5p, miR-205-5p, miR-221-3p, miR-375-3p, miR-382-5p, and miR-384-5p, contribute to aberrant Runx expression in prostate tumors. Our studies reveal a Runx/miRNA interaction axis centered on PTEN-PI3K-AKT signaling. This regulatory network translates to mechanistic understanding of prostate tumorigenesis that can be developed for diagnosis and directed therapy
Detection of a superconducting phase in a two-atom layer of hexagonal Ga film grown on semiconducting GaN(0001)
The recent observation of superconducting state at atomic scale has motivated
the pursuit of exotic condensed phases in two-dimensional (2D) systems. Here we
report on a superconducting phase in two-monolayer crystalline Ga films
epitaxially grown on wide band-gap semiconductor GaN(0001). This phase exhibits
a hexagonal structure and only 0.552 nm in thickness, nevertheless, brings
about a superconducting transition temperature Tc as high as 5.4 K, confirmed
by in situ scanning tunneling spectroscopy, and ex situ electrical
magneto-transport and magnetization measurements. The anisotropy of critical
magnetic field and Berezinski-Kosterlitz-Thouless-like transition are observed,
typical for the 2D superconductivity. Our results demonstrate a novel platform
for exploring atomic-scale 2D superconductor, with great potential for
understanding of the interface superconductivity
Room-temperature ferromagnetism in epitaxial bilayer FeSb/SrTiO3(001) terminated with a Kagome lattice
Two-dimensional (2D) magnets exhibit unique physical properties for potential
applications in spintronics. To date, most 2D ferromagnets are obtained by
mechanical exfoliation of bulk materials with van der Waals interlayer
interactions, and the synthesis of single or few-layer 2D ferromagnets with
strong interlayer coupling remains experimentally challenging. Here, we report
the epitaxial growth of 2D non-van der Waals ferromagnetic bilayer FeSb on
SrTiO3(001) substrates stabilized by strong coupling to the substrate, which
exhibits in-plane magnetic anisotropy and a Curie temperature above 300 K.
In-situ low-temperature scanning tunneling microscopy/spectroscopy and
density-functional theory calculations further reveal that a Fe Kagome layer
terminates the bilayer FeSb. Our results open a new avenue for further
exploring emergent quantum phenomena from the interplay of ferromagnetism and
topology for application in spintronics
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