86 research outputs found
On the topological surface states of the intrinsic magnetic topological insulator Mn-Bi-Te family
We review recent progress in the electronic structure study of intrinsic
magnetic topological insulators (MnBiTe)(BiTe)
() family. Specifically, we focus on the ubiquitously (nearly)
gapless behavior of the topological surface state Dirac cone observed by
photoemission spectroscopy, even though a large Dirac gap is expected because
of surface ferromagnetic order. The dichotomy between experiment and theory
concerning this gap behavior is perhaps the most critical and puzzling question
in this frontier. We discuss various proposals accounting for the lack of
magnetic effect on the topological surface state Dirac cone, which are mainly
categorized into two pictures, magnetic reconfiguration, and topological
surface state redistribution. Band engineering towards opening a magnetic gap
of topological surface states provides great opportunities to realize quantized
topological transport and axion electrodynamics at higher temperatures
Momentum-Resolved Visualization of Electronic Evolution in Doping a Mott Insulator
High temperature superconductivity in cuprates arises from doping a parent
Mott insulator by electrons or holes. A central issue is how the Mott gap
evolves and the low-energy states emerge with doping. Here we report
angle-resolved photoemission spectroscopy measurements on a cuprate parent
compound by sequential in situ electron doping. The chemical potential jumps to
the bottom of the upper Hubbard band upon a slight electron doping, making it
possible to directly visualize the charge transfer band and the full Mott gap
region. With increasing doping, the Mott gap rapidly collapses due to the
spectral weight transfer from the charge transfer band to the gapped region and
the induced low-energy states emerge in a wide energy range inside the Mott
gap. These results provide key information on the electronic evolution in
doping a Mott insulator and establish a basis for developing microscopic
theories for cuprate superconductivity.Comment: 23 pages, 5 figure
Diurnal RNAPII-tethered chromatin interactions are associated with rhythmic gene expression in rice
Background: The daily cycling of plant physiological processes is speculated to arise from the coordinated rhythms of gene expression. However, the dynamics of diurnal 3D genome architecture and their potential functions underlying the rhythmic gene expression remain unclear. Results: Here, we reveal the genome-wide rhythmic occupancy of RNA polymerase II (RNAPII), which precedes mRNA accumulation by approximately 2 h. Rhythmic RNAPII binding dynamically correlates with RNAPII-mediated chromatin architecture remodeling at the genomic level of chromatin interactions, spatial clusters, and chromatin connectivity maps, which are associated with the circadian rhythm of gene expression. Rhythmically expressed genes within the same peak phases of expression are preferentially tethered by RNAPII for coordinated transcription. RNAPII-associated chromatin spatial clusters (CSCs) show high plasticity during the circadian cycle, and rhythmically expressed genes in the morning phase and non-rhythmically expressed genes in the evening phase tend to be enriched in RNAPII-associated CSCs to orchestrate expression. Core circadian clock genes are associated with RNAPII-mediated highly connected chromatin connectivity networks in the morning in contrast to the scattered, sporadic spatial chromatin connectivity in the evening; this indicates that they are transcribed within physical proximity to each other during the AM circadian window and are located in discrete “transcriptional factory” foci in the evening, linking chromatin architecture to coordinated transcription outputs. Conclusion: Our findings uncover fundamental diurnal genome folding principles in plants and reveal a distinct higher-order chromosome organization that is crucial for coordinating diurnal dynamics of transcriptional regulation
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