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oe1(光电查) - 科学论文

11 条数据
?? 中文（中国） ▾

  • by angle-resolved photoelectron spectroscopy, scanning tunneling spectroscopy, and density functional theory

    摘要： The electronic structure of 1T -TaS2 showing a metal-insulator transition and a sequence of different charge density wave (CDW) transformations was discussed in the frame of variable temperature angle-resolved photoelectron spectroscopy (ARPES), scanning tunneling spectroscopy (STS), and density functional theory (DFT) calculations. For the commensurate charge density wave phase (CCDW) the Mott gap was estimated to be 0.4 eV and energy gaps (cid:2)CCDW,1, (cid:2)CCDW,2, (cid:2)B3-HHB, (cid:2)B4-B3 were observed. For the nearly commensurate charge density wave phase (NCCDW), the reminiscent of higher and lower Hubbard bands and a very pronounced electronic state associated with the parabolic band at the ˉ(cid:3) point in the Brillouin zone were identi?ed. The incommensurate charge density wave phase (ICCDW) showed a high value of local density of states at the Fermi level and a very pronounced edge of the metallic surface state located in the range of 0.15–0.20 eV above the Fermi level. The obtained STS and ARPES results were consistent with our theoretical calculations performed within DFT formalism including spin-orbit coupling.

    关键词： STS,1T -TaS2,charge density wave,ARPES,DFT,metal-insulator transition

    更新于2025-09-23 15:21:01

  • -Sn

    摘要： Gray tin, also known as α-Sn, can be turned into a three-dimensional topological insulator (3D-TI) by strain and finite-size effects. Such room-temperature 3D-TI is peculiarly interesting for spintronics due to the spin-momentum locking along the Dirac cone (linear dispersion) of the surface states. Angle-resolved photoemission spectroscopy (ARPES) has been used to investigate the dispersion close to the Fermi level in thin (001)-oriented epitaxially strained films of α-Sn for different film thicknesses as well as for different capping layers (Al, AlOx, and MgO). Indeed a proper capping layer is necessary to be able to use α-Sn surface states for spintronic applications. In contrast with free surfaces or surfaces coated with Ag, coating the α-Sn surface with Al or AlOx leads to a drop in the Fermi level below the Dirac point, and an important consequence for electronic transport is the presence of bulk states at the Fermi level. α-Sn films coated by AlOx are studied by electrical magnetotransport: Despite magnetotransport properties of the bulk electronic states of the Γ8 band playing an important role as suggested by ab initio calculations, there is clear evidence of surface states revealed by Shubnikov–de Haas oscillations corresponding to the ARPES observation.

    关键词： topological insulator,spin-momentum locking,α-Sn,Shubnikov–de Haas oscillations,Dirac cone,ARPES

    更新于2025-09-23 15:21:01

  • High resolution time- and angle-resolved photoemission spectroscopy with 11 eV laser pulses

    摘要： Performing time- and angle-resolved photoemission (tr-ARPES) spectroscopy at high momenta necessitates extreme ultraviolet laser pulses, which are typically produced via high harmonic generation (HHG). Despite recent advances, HHG-based setups still require large pulse energies (from hundreds of μJ to mJ) and their energy resolution is limited to tens of meV. Here, we present a novel 11 eV tr-ARPES setup that generates a flux of 5 × 1010 photons/s and achieves an unprecedented energy resolution of 16 meV. It can be operated at high repetition rates (up to 250 kHz) while using input pulse energies down to 3 μJ. We demonstrate these unique capabilities by simultaneously capturing the energy and momentum resolved dynamics in two well-separated momentum space regions of a charge density wave material ErTe3. This novel setup offers the opportunity to study the non-equilibrium band structure of solids with exceptional energy and time resolutions at high repetition rates.

    关键词： energy resolution,time- and angle-resolved photoemission spectroscopy,HHG,tr-ARPES,charge density wave,high repetition rates,high harmonic generation,ErTe3,11 eV laser pulses

    更新于2025-09-23 15:19:57

  • Why it is so hard to detect Luttinger liquids in angle resolved photo-emission spectroscopy?

    摘要： The problem of photoemission from a quasi-1D material is studied. We identify two issues that play a key role in the detection of gapless Tomonaga–Luttinger liquid (TLL) phase. Firstly, we show how a disorder—backward scattering as well as forward scattering component—is able to significantly obscure the TLL states, hence the initial state of angle resolved photo-emission spectroscopy (ARPES). Secondly, we investigate the photo-electron propagation towards a sample’s surface. We focus on the scattering path operator contribution to the final state of ARPES. We show that, in the particular conditions set by the 1D states, one can derive an exact analytical solution for this intermediate stage of ARPES. The solution shows that for particular energies of incoming photons the intensity of photo-current may be substantially reduced. Finally, we put together the two aspects (the disorder and the scattering path operator) to show the full, disruptive force of any inhomogeneities on the ARPES amplitude.

    关键词： nanotubes,Fresnel diffraction,quasi-1D materials,disorder,ARPES,Tomonaga–Luttinger liquids

    更新于2025-09-19 17:15:36

  • Synthesis of Monolayer Blue Phosphorus Enabled by Silicon Intercalation

    摘要： The growth of entirely synthetic two-dimensional (2D) materials could further expand the library of naturally occurring layered solids and provide opportunities to design materials with finely tunable properties. Among them, the synthesis of elemental 2D materials is of particular interest as they represent the chemically simplest case and serve as model system for exploring the on-surface synthesis mechanism. Here, a pure atomically-thin blue phosphorous (BlueP) monolayer is synthesized via silicon intercalation of the BlueP-Au alloy on Au(111). The intercalation process is characterized at the atomic scale by low-temperature scanning probe microscopy, and further corroborated by synchrotron radiation-based x-ray photoelectron spectroscopy measurements. The evolution of the band structures from BlueP-Au alloy into Si intercalated BlueP are clearly revealed by angle-resolved photoemission spectroscopy and further verified by density functional theory calculations.

    关键词： MBE,STM,Si intercalation,monolayer blue phosphorus,ARPES

    更新于2025-09-16 10:30:52

  • Anomalous doping evolution of nodal dispersion revealed by <i>in situ</i> ARPES on continuously doped cuprates

    摘要： We study the systematic doping evolution of nodal dispersions by in situ angle-resolved photoemission spectroscopy on the continuously doped surface of a high-temperature superconductor Bi2Sr2CaCu2O8+x and reveal that the nodal dispersion has three fundamentally different segments separated by two kinks, located at ～10 meV and roughly 70 meV, respectively. These three segments have different band velocities and different doping dependence. In particular, in the underdoped region the velocity of the high-energy segment increases monotonically as the doping level decreases and can even surpass the bare band velocity. We propose that electron fractionalization is a possible cause for this anomalous nodal dispersion and may even play a key role in the understanding of exotic properties of cuprates.

    关键词： electron fractionalization,high-temperature superconductors,nodal dispersion,ARPES,cuprates

    更新于2025-09-12 10:27:22

  • Extraction of tight binding parameters from in-situ ARPES on the continuously doped surface of cuprates

    摘要： Recently we developed a technique of ozone/vacuum annealing to continuously change the doping level of the surface of Bi2Sr2CaCu2O8+x and measured a nearly whole superconducting dome on one surface by in-situ angle-resolved photoemission spectroscopy [arXiv: 1805.06450]. Here we study the evolution of the electronic structures of Bi2Sr2CaCu2O8+x using this technique together with tight binding fits. The tight binding parameters are extracted to study their evolution with doping.

    关键词： cuprates,doping evolution,ARPES,electronic structures,tight binding

    更新于2025-09-10 09:29:36

  • Accurate and efficient data acquisition methods for high-resolution angle-resolved photoemission microscopy

    摘要： Angle-resolved photoemission spectroscopy (ARPES) is a powerful experimental technique in materials science, as it can directly probe electronic states inside solids in energy (E) and momentum (k) space. As an advanced technique, spatially-resolved ARPES using a well-focused light source (high-resolution ARPES microscopy) has recently attracted growing interests because of its capability to obtain local electronic information at micro- or nano-metric length scales. However, there exist several technical challenges to guarantee high precision in determining translational and rotational positions in reasonable measurement time. Here we present two methods of obtaining k-space mapping and real-space imaging in high-resolution ARPES microscopy. One method is for k-space mapping measurements that enables us to keep a target position on a sample surface during sample rotation by compensating rotation-induced displacements (tracing acquisition method). Another method is for real-space imaging measurements that significantly reduces total acquisition time (scanning acquisition method). We provide several examples of these methods that clearly indicate higher accuracy in k-space mapping as well as higher efficiency in real-space imaging, and thus improved throughput of high-resolution APRES microscopy.

    关键词： k-space mapping,ARPES,real-space imaging,Angle-resolved photoemission spectroscopy,high-resolution ARPES microscopy

    更新于2025-09-09 09:28:46

  • Bandgap Renormalization, Carrier Multiplication and Stark Broadening in Photoexcited Black Phosphorous

    摘要： We investigate black phosphorous by time and angle resolved photoelectron spectroscopy. The electrons excited by 1.57 eV photons, relax down to conduction band minimum within 1 ps. Despite the low bandgap value, no relevant amount of carrier multiplication could be detected at excitation density 3 ? 6 × 1019 cm?3. In the thermalized state, the bandgap renormalization is negligible up to a photoexcitation density that fills the conduction band by 150 meV. Astonishingly, a Stark broadening of the valence band takes place at an early delay time. We argue that electrons and holes with high excess energy lead to inhomogeneous screening of near surface fields. As a consequence the chemical potential is no longer pinned in a narrow impurity band.

    关键词： Stark,ARPES,Ultrafast,Black Phosphorous,Band-Gap-Renormalization

    更新于2025-09-04 15:30:14

  • Layer-by-Layer Graphene Growth on <i>β</i> -SiC/Si(001)

    摘要： The mechanism of few-layer graphene growth on the technologically-relevant cubic-SiC/Si(001) substrate is uncovered using high-resolution core-level and angle-resolved photoelectron spectroscopy, low-energy electron microscopy, and micro-spot low-energy electron diffraction. The thickness of the graphitic overlayer supported on the silicon carbide substrate and related changes in the surface structure are precisely controlled by monitoring the progress of the surface graphitization in-situ during high-temperature graphene synthesis, using a combination of micro-spectroscopic techniques. The experimental data reveal gradual changes in the preferential graphene lattice orientations at the initial stages of the few-layer graphene growth on SiC(001) and can act as reference data for controllable growth of single-, double-, and triple-layer graphene on silicon carbide substrates.

    关键词： LEEM,ARPES,μ-LEED,β-SiC,XPS,nanodomains,graphene

    更新于2025-09-04 15:30:14