A5101604339- Physics of Superconductivity and Magnetism
- Iron-based superconductors research
- Advanced Condensed Matter Physics
- Cold Atom Physics and Bose-Einstein Condensates
- Magnetic and transport properties of perovskites and related materials
- Atomic and Molecular Physics
- Nuclear physics research studies
- Organic and Molecular Conductors Research
- Semiconductor Quantum Structures and Devices
- Electronic and Structural Properties of Oxides
- Advanced Chemical Physics Studies
- Rare-earth and actinide compounds
- Quantum, superfluid, helium dynamics
- Thermal Radiation and Cooling Technologies
- Thin-Film Transistor Technologies
- Strong Light-Matter Interactions
- High-pressure geophysics and materials
- Surface and Thin Film Phenomena
- Topological Materials and Phenomena
- Inorganic Chemistry and Materials
- Advanced Thermodynamics and Statistical Mechanics
- Corporate Taxation and Avoidance
- 2D Materials and Applications
- Muon and positron interactions and applications
- Graphene research and applications
SLAC National Accelerator Laboratory
2010-2015
Stanford University
2008-2015
Josef Meissner (Germany)
2015
University of Kaiserslautern
2013
Fraunhofer Institute for Laser Technology
2008-2010
Max Planck Institute for Nuclear Physics
1990-2010
Technical University of Darmstadt
1996-2009
Stanford Synchrotron Radiation Lightsource
2008
Freie Universität Berlin
2008
Fritz Haber Institute of the Max Planck Society
2008
Obtaining insight into microscopic cooperative effects is a fascinating topic in condensed matter research because, through self-coordination and collectivity, they can lead to instabilities with macroscopic impacts like phase transitions. We used femtosecond time- angle-resolved photoelectron spectroscopy (trARPES) optically pump probe TbTe 3 , an excellent model system which study these effects. drove transient charge density wave melting, excited collective vibrations observed them their...
A detailed phenomenology of low energy excitations is a crucial starting point for microscopic understanding complex materials, such as the cuprate high-temperature superconductors. Because its unique momentum-space discrimination, angle-resolved photoemission spectroscopy (ARPES) ideally suited this task in cuprates, where emergent phases, particularly superconductivity and pseudogap, have anisotropic gap structure momentum space. We present comprehensive doping- temperature-dependence...
Establishing the appropriate theoretical framework for unconventional superconductivity in iron-based materials requires correct understanding of both electron correlation strength and role Fermi surfaces. This fundamental issue becomes especially relevant with discovery iron chalcogenide superconductors. Here, we use angle-resolved photoemission spectroscopy to measure three representative chalcogenides, FeTe0.56Se0.44, monolayer FeSe grown on SrTiO3 K0.76Fe1.72Se2. We show that these...
Using a new bunched-beam technique in the GSI heavy-ion experimental storage ring (ESR), we performed precision laser spectroscopy on relativistic heavy ions hitherto inaccessible infrared optical region. We determined wavelength of $M1$ transition between $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$ $(\ensuremath{\tau}\ensuremath{\approx}50\mathrm{ms})$ and $F\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}0$ hyperfine states $1s$ ground state hydrogenlike...
We characterize the occupied and unoccupied electronic structure of topological insulator ${\mathrm{Bi}}_{2}{\mathrm{Se}}_{3}$ by one-photon two-photon angle-resolved photoemission spectroscopy slab band calculations. reveal a second, Dirac surface state with similar physical origin to well-known state. This is energetically located 1.5 eV above conduction band, which permits it be directly excited output Ti:sapphire laser. discovery demonstrates feasibility direct ultrafast optical coupling...
The improved resolution of laser-based angle-resolved photoemission spectroscopy (ARPES) allows reliable access to fine structures in the spectrum. We present a systematic, doping-dependent study recently discovered low-energy kink nodal dispersion Bi2Sr2CaCu2O(8+δ) (Bi-2212), which demonstrates ubiquity and robustness this underdoped Bi-2212. renormalization velocity due becomes stronger with underdoping, revealing that Fermi is nonuniversal, contrast assumed phenomenology. This used...
Gaining insights into the mechanisms of how order and broken symmetry emerges from many-particle interactions is a major challenge in solid state physics. Most experimental techniques—such as angle-resolved photoemission spectroscopy (ARPES)—probe single-particle excitation spectrum extract information about ordering mechanism collective effects, often indirectly through theory. Time-resolved ARPES (tr-ARPES) makes dynamics system after optical directly visible their influence on...
Abstract Non-equilibrium conditions may lead to novel properties of materials with broken symmetry ground states not accessible in equilibrium as vividly demonstrated by non-linearly driven mid-infrared active phonon excitation. Potential energy surfaces electronically excited also allow direct nuclear motion, but relaxation the excess typically excites fluctuations leading a reduced or even vanishing order parameter characterized an electronic gap. Here, using femtosecond time- and...
Recently, angle-resolved photoemission spectroscopy (ARPES) has been used to highlight an anomalously large band renormalization at high binding energies in cuprate superconductors: the energy 'waterfall' or anomaly (HEA). This paper demonstrates, using a combination of new ARPES measurements and quantum Monte Carlo simulations, that HEA is not simply by-product matrix element effects, but rather represents cross-over from quasi-particle low near Fermi level valence bands higher energy,...
The prevalent view of the high-temperature superconducting cuprates is that their essential low-energy physics captured by local Coulomb interactions. However, this been challenged recently studies indicating importance longer-range components. Motivated this, we demonstrate these components examining electron-phonon ($e$-ph) interaction with acoustic phonons in connection discovered renormalization near-nodal ($\ensuremath{\sim}8--15\text{ }\text{ }\mathrm{meV}$) dispersion...
In this work we present high-resolution angle resolved ultraviolet photoelectron spectroscopy on the system $\mathrm{Ag}∕\mathrm{Cu}(111)$. For 1 ML Ag one obtains well-known quasicommensurate triangular reconstruction for which observe opening of a band gap in Shockley state at parallel momentum ${k}_{\ensuremath{\Vert}}\ensuremath{\approx}0.151\phantom{\rule{0.3em}{0ex}}{\mathrm{\AA{}}}^{\ensuremath{-}1}$ as consequence Bragg reflection new zone boundaries supercell. The position $k$ space...
We demonstrate the capability of growing high quality ultrathin films topological insulators Bi2Se3 and Bi2Te3 using molecular beam epitaxy. Unlike previous growth techniques, which often pin Fermi energy in conduction band for samples, our samples remain intrinsic bulk insulators. characterize these in-situ angle resolved photoemission spectroscopy (ARPES), is a direct probe bandstructure, ex-situ atomic force microscopy. find that lies above energy, indicating insulating behavior with only...
We present ultrahigh resolution angle-resolved photoemission data of the prototypical Kondo lattice system YbRh${}_{2}$Si${}_{2}$, using a 7 eV laser photon source. Detailed temperature dependent measurements reveal development coherent states, in form sharp, weakly dispersing peaks at lowest energy single-electron spectra, below characteristic temperature. The temperature, obtained from photoemission, is intriguingly exactly same scale as and lifetime state.
We report findings of strong anomalies in both mutual inductance and inelastic Raman spectroscopy measurements single-unit-cell FeSe film grown on Nb-doped ${\mathrm{SrTiO}}_{3}$, which occur near the temperature where superconductinglike energy gap opens. Analysis suggests that anomaly is associated with a broadened ferroelectric transition thin layer $\mathrm{FeSe}/{\mathrm{SrTiO}}_{3}$ interface. The coincidence gap-opening temperatures adds credence to central role played by...
Spatial power modulation for laser beam micro welding by superposing an oscillation movement to the feed direction is gaining more and importance, especially of difficultto-weld materials, e.g.aluminum, copper or zinc-coated steel sheets.Up now, there are no adequate machine techniques available providing frequencies than 5 kHz.Examinations about dynamic behavior conventional galvanometric scanners with integrated ("wobble function") presented.These systems commonly used but their at high...
Ultrathin FeSe films grown on SrTiO3 substrates are a recent milestone in atomic material engineering due to their important role understanding unconventional superconductivity Fe-based materials. By using femtosecond time- and angle-resolved photoelectron spectroscopy, we study phonon frequencies ultrathin FeSe/SrTiO3 by molecular beam epitaxy. After optical excitation, observe periodic modulations of the spectrum as function pump-probe delay for 1-unit-cell, 3-unit-cell, 60-unit-cell thick...
Recently, angle-resolved photoemission spectroscopy (ARPES) has revealed a dispersion anomaly at high binding energy near $0.3--0.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ in various families of the high-temperature superconductors. For further studies this anomaly, we present new two-dimensional fitting scheme and apply it to high-statistics ARPES data strongly overdoped ${\mathrm{Bi}}_{2}{\mathrm{Sr}}_{2}\mathrm{Cu}{\mathrm{O}}_{6}$ cuprate superconductor. The procedure allows us extract...
We performed angle-resolved photoemission and optical studies on electron-doped high-temperature superconductors (HTSCs), compared the results with various theoretical models. Based fit to experimental data, we conclude that itinerant electrons in nonmagnetic phase predominantly couple fluctuations of remnant antiferromagnetic (AF) order, rather than spin excitations derived from particle-hole pairs. Our observation naturally accounts for pseudogap phenomenon other facts HTSCs terms size...