A5047244757- Electronic and Structural Properties of Oxides
- Graphene research and applications
- Magnetic and transport properties of perovskites and related materials
- Topological Materials and Phenomena
- Advanced Condensed Matter Physics
- Physics of Superconductivity and Magnetism
- 2D Materials and Applications
- Quantum and electron transport phenomena
- Surface and Thin Film Phenomena
- Magnetic properties of thin films
- Semiconductor materials and devices
- Rare-earth and actinide compounds
- ZnO doping and properties
- Iron-based superconductors research
- Ferroelectric and Piezoelectric Materials
- Advanced Chemical Physics Studies
- Chalcogenide Semiconductor Thin Films
- Inorganic Chemistry and Materials
- Electron and X-Ray Spectroscopy Techniques
- Copper-based nanomaterials and applications
- Fullerene Chemistry and Applications
- Organic and Molecular Conductors Research
- Multiferroics and related materials
- Ferroelectric and Negative Capacitance Devices
- MXene and MAX Phase Materials
Lawrence Berkeley National Laboratory
2016-2025
University of California, Berkeley
2020-2025
Advanced Light Source
2013-2024
Cornell University
2019-2023
Interface (United States)
2023
Material Sciences (United States)
2023
Pohang University of Science and Technology
2016-2017
Institute for Basic Science
2016
École Polytechnique Fédérale de Lausanne
2006-2011
European Synchrotron Radiation Facility
2008
Surface alloying is shown to produce electronic states with a very large spin-splitting. We discuss the long range ordered bismuth/silver(111) surface alloy where an energy bands separation of up one eV achieved. Such strong spin-splitting enables angular resolved photoemission spectroscopy directly observe region close band edge, density shows quasi-one dimensional behavior. The associated singularity in local has been measured by low temperature scanning tunneling spectroscopy....
The manipulation of the bandgap graphene by various means has stirred great interest for potential applications. Here we show that treatment with xenon difluoride produces a partially fluorinated (fluorographene) covalent C−F bonding and local sp3-carbon hybridization. material was characterized Fourier transform infrared spectroscopy, Raman electron energy loss photoluminescence near edge X-ray absorption spectroscopy. These results confirm structural features fluorographane 3.8 eV, close...
Oxygen vacancies created in anatase TiO(2) by UV photons (80-130 eV) provide an effective electron-doping mechanism and induce a hitherto unobserved dispersive metallic state. Angle resolved photoemission reveals that the quasiparticles are large polarons. These results indicate can be tuned from insulator to polaron gas weakly correlated metal as function of doping clarify nature conductivity this material.
Two-dimensional (2D) van-der-Waals semiconductors have emerged as a class of materials with promising device characteristics owing to the intrinsic bandgap. For realistic applications, ideal is modify bandgap in controlled manner by mechanism that can be generally applied this materials. Here, we report observation universally tunable family bulk 2H transition metal dichalcogenides (TMDs) situ surface doping Rb atoms. A series angle-resolved photoemission spectra unexceptionally shows TMDs...
We observe a giant spin-orbit splitting in bulk and surface states of the non-centrosymmetric semiconductor BiTeI. show that Fermi level can be placed valence or conduction band by controlling termination. In both cases it intersects spin-polarized bands, corresponding depletion accumulation layers. The momentum these bands is not affected adsorbate-induced changes potential. These findings demonstrate two properties crucial for enabling semiconductor-based spin electronics -- large, robust...
The electronic structure of graphene on Cu(111) and Cu(100) single crystals is investigated using low energy electron microscopy, diffraction angle resolved photoemission spectroscopy. On both substrates the rotationally disordered interactions between substrate lead to a shift in Dirac crossing $\sim$ -0.3 eV opening 250 meV gap. Exposure samples air resulted intercalation oxygen under Cu(100), which formed ($\sqrt{2} \times 2\sqrt{2}$)R45$^{\rm o}$ superstructure. effect this $\pi$ bands...
We employ angle-resolved photoemission spectroscopy (ARPES) to investigate the electronic structures of two rotational variants epitaxial, single-layer graphene on Ir(111). As grown, more-abundant R0 variant is nearly charge-neutral, with strong hybridization between and Ir bands near Fermi level. The surface its replicas exactly coincide Van Hove singularities in surface. Sublattice symmetry breaking introduces a small gap-inducing potential at Dirac crossing, which revealed by n-doping...
We present a method for decoupling epitaxial graphene grown on SiC(0001) by intercalation of layer fluorine at the interface. The atoms do not enter into covalent bond with graphene, but rather saturate substrate Si bonds. This configuration induces remarkably large hole density p \approx 4.5 \times 1013 cm-2, equivalent to location Fermi level 0.79 eV above Dirac point ED .
Trigonal tellurium, a small-gap semiconductor with pronounced magneto-electric and magneto-optical responses, is among the simplest realizations of chiral crystal. We have studied by spin- angle-resolved photoelectron spectroscopy its unconventional electronic structure unique spin texture. identify Kramers-Weyl, composite, accordionlike Weyl fermions, so far only predicted theory, show that polarization parallel to wave vector along lines in k space connecting high-symmetry points. Our...
In Kagome metal CsV$_3$Sb$_5$, multiple intertwined orders are accompanied by both electronic and structural instabilities. These exotic have attracted much recent attention, but their origins remain elusive. The newly discovered CsTi$_3$Bi$_5$ is a Ti-based to parallel CsV$_3$Sb$_5$. Here, we report angle-resolved photoemission experiments first-principles calculations on pristine Cs-doped samples. Our results reveal that the van Hove singularity (vHS) in can be tuned large energy range...
We demonstrate that it is possible to tune the Rashba energy, introduced by a strong spin-orbit splitting, and Fermi energy in two-dimensional electron gas controlled change of stoichiometry an artificial surface alloy. In ${\mathrm{Bi}}_{x}{\mathrm{Pb}}_{1\ensuremath{-}x}∕\mathrm{Ag}(111)$ alloy, interaction maintains dramatic influence on band dispersion for arbitrary Bi concentration $x$, as shown angle-resolved photoelectron spectroscopy. The ${E}_{R}$ ${E}_{F}$ can be tuned achieve...
Electron-plasmon coupling in graphene has recently been shown to give rise a "plasmaron" quasiparticle excitation. The strength of this predicted depend on the effective screening, which turn is expected dielectric environment sheet. Here we compare enviromental screening for four different substrates by evaluating separation plasmaron bands from hole using Angle Resolved PhotoEmission Spectroscopy. Comparison with G0W-RPA predictions are used determine constant underlying substrate layer....
The interfaces between two condensed phases often exhibit emergent physical properties that can lead to new physics and novel device applications are the subject of intense study in many disciplines. We here apply experimental theoretical techniques characterization one such interesting interface system: two-dimensional electron gas (2DEG) formed multilayers consisting $\mathrm{SrTi}{\mathrm{O}}_{3}$ (STO) $\mathrm{GdTi}{\mathrm{O}}_{3}$ (GTO). This system has been multiple studies recently...
We have studied by angle-resolved photoelectron spectroscopy (ARPES) the band structure of ordered surface alloy obtained deposition 0.33 monolayers Pb on Ag(111) surface. observe several dispersing features which are well described as Pb-Ag hybrid bands a calculation performed within generalized gradient approximation density functional theory. also find that mixed ${p}_{z}$ and Ag $s$ character is split in momentum space. interpret this splitting combined result spin-orbit interaction...
We demonstrate that the spin-orbit coupling of two-dimensional surface states can be detected locally by scanning-tunneling spectroscopy (STS). The spin splitting state induces a singularity in local density which as distinct peak differential conductance spectrum. From STS spectrum we determine Rashba energy measure strength splitting. Its detection and imaging are demonstrated for alloys Bi Pb on Ag(111), exhibit particularly large spin-split band structures. influence surface-state...
We have studied by angle-resolved photoelectron spectroscopy the ordered $X{\text{Cu}}_{2}$ surface alloys formed $X=\text{Sb}$ and Bi on a Cu(111) substrate. found clear analogies with corresponding $X{\text{Ag}}_{2}$ same elements Ag(111). The electronic states near Fermi level are similarly split spin-orbit (SO) interaction smaller splitting in reflecting atomic SO parameter of Cu vs Ag. charge transfer from Sb adatoms to substrate atoms their outward relaxation different for two...
A novel method is demonstrated to tailor the electronic structure of high-Z surface alloys showing a giant Rashba splitting by means electron doping. This aims for new model systems study unconvential spin topologies and possible applications in field spintronics. We give insights into origin enhanced effect two specific Bi/Cu(111) Bi/Ag(111) employing angle-resolved photoelectron spectroscopy first-principles calculations.
The transport properties of zirconium pentatelluride ZrTe${}_{5}$, where the sign carriers changes with temperature, have so far eluded a clear understanding. In this work, authors investigate by angle-resolved photoemission temperature dependence low-energy electronic bands, and find that behavior can be explained presence van Hove singularity in density states. By surface doping alkali atoms, also access unoccupied states conduction band define material as being weak topological insulator.
In nodal-line semimetals linearly dispersing states form Dirac loops in the reciprocal space, with high degree of electron-hole symmetry and almost-vanishing density near Fermi level. The result is reduced electronic screening enhanced correlations between quasiparticles. Here we investigate structure ZrSiSe, by combining time- angle-resolved photoelectron spectroscopy ab initio functional theory (DFT) complemented an extended Hubbard model (DFT +U +V). We show that are on ultrashort...
Screening, a ubiquitous phenomenon associated with the shielding of electric fields by surrounding charges, has been widely adopted as means to modify material’s properties. While most studies have relied on static changes screening through doping or gating thus far, here we demonstrate that can also drive onset distinct quantum states ultrafast timescale. By using time- and angle-resolved photoemission spectroscopy, show intense optical excitation 1T-TiSe 2 , prototypical charge density...
We have studied the electronic structure of $\text{Ag}(111)(\sqrt{3}\ifmmode\times\else\texttimes\fi{}\sqrt{3})R30\ifmmode^\circ\else\textdegree\fi{}\text{-Sb}$ surface alloy by angle-resolved photoemission. find two hybrid bands, similar to isostructural Ag(111)-Bi interface. The spin-orbit coupling induced spin splitting in momentum space, however, is strongly reduced from Bi case. First-principles and model band calculations correctly reproduce this difference. present results illustrate...
We report the momentum-resolved measurement of a two-dimensional electron gas at LaTiO(3)/SrTiO(3) interface by angle-resolved photoemission spectroscopy (ARPES). Thanks to an advanced sample preparation technique, orbital character conduction electrons and electronic correlations can be accessed quantitatively as each unit cell layer is added. find that all these quantities change dramatically with distance from interface. These findings open way analogous studies on other heterostructures,...