345 research outputs found
Identification of HSP90 gene from the Chinese oak silkworm, Antheraea pernyi
The heat shock proteins (Hsp) play an important role in protein folding and protection of cells from stress. To investigate the role of Hsp90 in silk-producing insect Antheraea pernyi (Lepidoptera: Saturniidae), a full-length cDNA encoding Hsp90 from A. pernyi was cloned, sequenced and characterized. The complete cDNA (2,482 bp) contained a 2,154 bp open reading frame encoding 717 amino acid residues and had 94.5% identity with Antheraea yamamai Hsp90. The relative expression levels of Hsp90 in five different tissues at normal and high temperatures were evaluated with real-time fluorescence quantitative RT-PCR. The expression of Hsp90 was obviously changed in the examined tissues except for fat bodies after induced by high temperature. SDS-PAGE of purified protein demonstrated that an 86 KD recombinant protein was successfully expressed in transformed Escherichia coli cells. These results shed light on studying the mechanism of tolerance in A. pernyi.Key words: Antheraea pernyi, HSP90, sequence analysis, expression
Weyl, Dirac and high-fold chiral fermions in topological quantum materials
Quantum materials hosting Weyl fermions have opened a new era of research in
condensed matter physics. First proposed in 1929 in particle physics, Weyl
fermions have yet to be observed as elementary particles. In 2015, Weyl
fermions were detected as collective electronic excitations in the strong
spin-orbit coupled material tantalum arsenide, TaAs. This discovery was
followed by a flurry of experimental and theoretical explorations of Weyl
phenomena in materials. Weyl materials naturally lend themselves to the
exploration of the topological index associated with Weyl fermions and their
divergent Berry curvature field, as well as the topological bulk-boundary
correspondence giving rise to protected conducting surface states. Here, we
review the broader class of Weyl topological phenomena in materials, starting
with the observation of emergent Weyl fermions in the bulk and of Fermi arc
states on the surface of the TaAs family of crystals by photoemission
spectroscopy. We then discuss some of the exotic optical and magnetic responses
observed in these materials, as well as the progress in developing some of the
related chiral materials. We discuss the conceptual development of high-fold
chiral fermions, which generalize Weyl fermions, and we review the observation
of high-fold chiral fermion phases by taking the rhodium silicide, RhSi, family
of crystals as a prime example. Lastly, we discuss recent advances in Weyl-line
phases in magnetic topological materials. With this Review, we aim to provide
an introduction to the basic concepts underlying Weyl physics in condensed
matter, and to representative materials and their electronic structures and
topology as revealed by spectroscopic studies. We hope this work serves as a
guide for future theoretical and experimental explorations of chiral fermions
and related topological quantum systems with potentially enhanced
functionalities.Comment: To appear in Nature Review Material
Negative flat band magnetism in a spin-orbit coupled correlated kagome magnet
It has long been speculated that electronic flat band systems can be a
fertile ground for hosting novel emergent phenomena including unconventional
magnetism and superconductivity. Although flat bands are known to exist in a
few systems such as heavy fermion materials and twisted bilayer graphene, their
microscopic roles and underlying mechanisms in generating emergent behavior
remain elusive. Here we use scanning tunneling microscopy to elucidate the
atomically resolved electronic states and their magnetic response in the kagome
magnet Co3Sn2S2. We observe a pronounced peak at the Fermi level, which is
identified to arise from the kinetically frustrated kagome flat band.
Increasing magnetic field up to +-8T, this state exhibits an anomalous
magnetization-polarized Zeeman shift, dominated by an orbital moment in
opposite to the field direction. Such negative magnetism can be understood as
spin-orbit coupling induced quantum phase effects tied to non-trivial flat band
systems. We image the flat band peak, resolve the associated negative
magnetism, and provide its connection to the Berry curvature field, showing
that Co3Sn2S2 is a rare example of kagome magnet where the low energy physics
can be dominated by the spin-orbit coupled flat band. Our methodology of
probing band-resolved ordering phenomena such as spin-orbit magnetism can also
be applied in future experiments to elucidate other exotic phenomena including
flat band superconductivity and anomalous quantum transport.Comment: Nature Physics onlin
Atomic-scale visualization of quasiparticle interference on a type-II Weyl semimetal surface
We combine quasiparticle interference simulation (theory) and atomic
resolution scanning tunneling spectro-microscopy (experiment) to visualize the
interference patterns on a type-II Weyl semimetal MoWTe for
the first time. Our simulation based on first-principles band topology
theoretically reveals the surface electron scattering behavior. We identify the
topological Fermi arc states and reveal the scattering properties of the
surface states in MoWTe. In addition, our result reveals
an experimental signature of the topology via the interconnectivity of bulk and
surface states, which is essential for understanding the unusual nature of this
material.Comment: To appear in Phys. Rev. Let
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