Time-resolved ARPES with probe energy of 6.0/7.2 eV and switchable resolution configuration.

We present a detailed exposition of the design for time- and angle-resolved photoemission spectroscopy using a UV probe laser source that combines the nonlinear effects of ß-BaB2O4 and KBe2BO3F2 optical crystals. The photon energy of the probe laser can be switched between 6.0 and 7.2 eV, with the flexibility to operate each photon energy setting under two distinct resolution configurations. Under the fully optimized energy resolution configuration, we achieve an energy resolution of 8.5 meV at 6.0 eV and 10 meV at 7.2 eV. Alternatively, switching to the other configuration enhances the temporal resolution, yielding a temporal resolution of 72 fs for 6.0 eV and 185 fs for 7.2 eV. We validated the performance and reliability of our system by applying it to measuring two typical materials: the topological insulator MnBi2Te4 and the excitonic insulator candidate Ta2NiSe5.

Time-resolved ARPES with tunable 12-21.6 eV XUV at 400 kHz repetition rate.

Time-resolved and angle-resolved photoemission spectroscopy (trARPES) is a powerful method to detect the non-equilibrium electronic structure in solid systems. In this study, we report a trARPES apparatus with tunable photon energy selectively among 12, 16.8, and 21.6 eV at a repetition rate of 400 kHz. The energy and temporal resolutions of the three harmonics are determined as 104/111/157 meV and 276/190/154 fs, respectively. The photon flux on the sample is estimated to be 1010-1011 photons/s by using a photodiode. Finally, the performance of this setup is verified by both equilibrium and non-equilibrium ARPES measurements on topological materials Zr2Te2P and Bi2Se3. Meanwhile, the importance of the tunability of the extreme ultraviolet (XUV) source is highlighted by comparing experimental results measured with the three different photon energies.

High-flux wavelength tunable XUV source in the 12-40.8†eV photon energy range with adjustable energy and time resolution for Tr-ARPES applications.

High-order harmonic generation (HHG) has a broad spectrum covering vacuum ultraviolet to extreme ultraviolet (XUV) bands, which is useful for applications involving material analyses at different information depths. Such an HHG light source is perfect for time- and angle-resolved photoemission spectroscopy. Here, we demonstrate a high-photon flux HHG source driven by a two-color field. Applying a fused silica compression stage to reduce the driving pulse width, we obtained a high XUV photon flux of 2 × 1012 phs/s @21.6 eV on target. We designed a classical diffraction mounted (CDM) grating monochromator that can achieve a wide range of photon energy from 12 to 40.8 eV, while the time resolution is improved by reducing the pulse front tilt after the harmonic selection. We designed a spatial filtering method to adjust the time resolution using the CDM monochromator and significantly reduced the pulse front tilt of the XUV pulses. We also demonstrate a detailed prediction of the energy resolution broadening which is caused by the space charge effect.

Relationship between Antisite Defects, Magnetism, and Band Topology in MnSb2Te4 Crystals with TC ≈ 40 K.

MnSb2Te4 has attracted extensive attention because of its rich and adjustable magnetic properties. Here, using a modified crystal growth method, ferrimagnetic MnSb2Te4 crystals with enhanced Curie temperature (TC) of about 40 K with dominant hole-type carriers and intrinsic anomalous Hall effect is obtained. Time- and angle-resolved photoemission spectroscopy reveals that surface states are absent in both antiferromagnetic and ferrimagnetic MnSb2Te4, implying that they have topologically trivial electronic structures. We propose that the enhancement of ferrimagnetism mainly originates from the increase of intralayer magnetic coupling caused by the decrease of Sb content at Mn sites when the decrease of Mn concentration at Sb sites would prefer the nontrival band topology. Moreover, it is known that the initial saturation moment (Mis) is sensitive to the concentrations of Mn/Sb antisite defects; thus, the Mis could be a valuable parameter to evaluate the magnetic and topological properties of MnX2nTe3n+1 (X = Bi, Sb) families.

Induction of transforming growth factor-beta 1 on dentine pulp cells in different culture patterns.

Recent studies have documented that TGF-beta1 takes part in dental pulp tissue repair. Moreover, dental pulp cells have the potential to differentiate into odontoblast-like cells and produce reparative dentine in this process. However, the molecular mechanisms and potential interactions between TGF-beta1 and dental pulp cells are not clear due to the complexity of the pulp/dentine microenvironment. In this study, we investigated the induction of TGF-beta1 on the dental pulp cells in cell culture, tissue culture and three-dimensional culture patterns. These results demonstrated that TGF-beta1 significantly increased the proliferation of cells and activity of ALPase. Dental pulp cells cultured in the presence of TGF-beta1 formed mineralization nodules. In the organ culture, dental pulp cells treated with TGF-beta1 differentiated into odontoblast-like cells and formed a pulp-dentinal complex; and TGF-beta1 significantly induced synthesis of dentine relative proteins DSPP, DMP-1. The dental pulp cells share some characteristics of the odontoblast, such as a parallel arrangement with columnar form and a unilateral cell process. Together, these data indicate that TGF-beta1 can make dental pulp cells differentiated into odontoblast-like cells and form the pulp-dentinal complex. Moreover, these results suggest that TGF-beta1 is an important regulatory factor in odontoblast differentiation during tooth development and pulp repair.