Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session A27: Focus Session: Emerging Ultrafast Technologies I |
Hide Abstracts |
Sponsoring Units: DCP Chair: Andrei Tokmakoff, University of Chicago Room: 204B |
Monday, March 2, 2015 8:00AM - 8:36AM |
A27.00001: Recent Progress in the Study of Single Molecule Chemistry at the Nanometer Length Scale and Picosecond Time Scale Invited Speaker: Richard Van Duyne During the last few years, there has been an explosion of interest and activity in the field of plasmonics. The goal of plasmonics is to control and manipulate light on the nanometer length scale using the properties of the collective electronic excitations in noble metal films or nanoparticles, known as surface plasmons. An improved understanding of the interactions between adsorbed molecules and plasmonic nanostructures (i.e., molecular plasmonics) is having a significant impact in a number of research areas including electrochemistry, surface science, catalysis for energy conversion and storage, the materials science of nanoparticles, biomedical diagnostics, art conservation science, and nanolithography. In the first part of this lecture, I will provide some background material on the basic physical concepts underlying molecular plasmonics with an emphasis on surface-enhanced Raman spectroscopy (SERS), localized surface plasmon resonance (LSPR) spectroscopy, and tip-enhanced Raman spectroscopy (TERS). In the second part of this lecture, I will focus in on three recent advances in TERS which illustrate the power of this nanoscale vibrational spectroscopy. First, new insights into the nature of the relative intensity fluctuations in single molecule tip-enhanced Raman spectroscopy (SMTERS) will be discussed. Second, our current understanding of the adsorbate surface interactions involved in the low temperature (LT), ultrahigh vacuum (UHV) TERS of the Ag tip/Rhodamine 6G (R6G) /Ag(111) system will be described. Finally, an update on our new results in coupling ultrafast lasers with TERS. This last topic illuminates a path forward toward the goal of understanding chemistry at the space-time limit. [Preview Abstract] |
Monday, March 2, 2015 8:36AM - 8:48AM |
A27.00002: Coherent two-dimensional infrared microscopy Carlos Baiz, Denise Schach, Andrei Tokmakoff We developed ultrafast 2D IR spectral microscopy, a new technique to measure spatially-resolved 2D infrared spectra and vibrational dynamics with diffraction-limited spatial resolution and femtosecond time resolution. The key enabling development consists of a new geometry where all three IR pulses propagate fully collinearly through an all-reflective IR microscope. A combination of polarization, chopping, and phase-cycling isolate the 2D IR signal by removing all unwanted signal and interference contributions. The single-beam collinear geometry enables us to implement 2D IR in three configurations: transmission, reflectance, and ATR. In terms of sensitivity, the 6 micron focus size produces an 8-fold enhancement of the signal compared to focusing with standard parabolic mirrors. These methods open up new possibilities for imaging proteins in cells, lipid membranes, or vesicles, as well as performing surface-sensitive studies on biological systems. [Preview Abstract] |
Monday, March 2, 2015 8:48AM - 9:24AM |
A27.00003: Mapping the nanoscale energetic landscape in conductive polymer films with spatially super-resolved exciton dynamics Invited Speaker: Naomi Ginsberg The migration of Frenkel excitons, tightly-bound electron-hole pairs, in polymeric organic semiconducting films is critical to the efficiency of bulk heterojunction solar cells. While these materials exhibit a high degree of structural heterogeneity on the nanoscale, traditional measurements of exciton diffusion lengths are performed on bulk samples. Since both the characteristic length scales of structural heterogeneity and the reported bulk diffusion lengths are smaller than the optical diffraction limit, we adapt far-field super-resolution fluorescence imaging to uncover the correlations between the structural and energetic landscapes that the excitons explore. [Preview Abstract] |
Monday, March 2, 2015 9:24AM - 10:00AM |
A27.00004: Ultrafast electron microscopy and diffraction with laser-driven field emitters Invited Speaker: Claus Ropers Ultrafast structural dynamics in solids and nanostructures can be investigated by an increasing number of sophisticated electron and x-ray diffraction techniques. Electrons are particularly suited for this purpose, exhibiting high scattering cross-sections and allowing for beam control by versatile electrostatic or magnetic lens systems. The capabilities of time-resolved electron imaging techniques critically depend on the employed source of laser-driven ultrashort electron pulses. Nanoscopic sources offer exceptional possibilities for the generation of electron probe pulses with very short durations and high spatial beam coherence. In this talk, I will discuss recent progress in the development of ultrafast electron microscopy and diffraction based on nanoscopic photocathodes. In particular, we implemented ultrafast low-energy electron diffraction (ULEED) and ultrafast transmission electron microscopy (UTEM) driven by nonlinear photoemission from field emission tips. ULEED enables the study of structural changes with high temporal resolution and ultimate surface sensitivity, at sub-keV electron energies. As a first application of this technique, we studied the structural phase transition in a stripe-like polymer superstructure on freestanding monolayer graphene.\footnote{M. Gulde \textit{et al.}, Science \textbf{345}, 200 (2014)} An advanced UTEM instrument was realized by custom modifications of a standard transmission electron microscope, leading to electron focal spot sizes in the microscope's sample plane of about 10 nm and electron pulse durations of less than 700 fs. Utilizing these features, we investigate the quantum-coherent interaction between the ultrashort electron pulse and the optical near-field of an illuminated nanostructure.\footnote{A. Feist \textit{et al.}, submitted} Finally, further applications and prospects of ultrafast electron imaging, diffraction and spectroscopy using nanoscale field emitters will be discussed. [Preview Abstract] |
Monday, March 2, 2015 10:00AM - 10:12AM |
A27.00005: Time Resolved Imaging at 10GHz and Beyond Using the SSRL Scanning Transmission X-ray Microscope Hendrik Ohldag, Stefano Bonetti, Roopali Kukreja, Zhao Chen, Joseph Frisch, Hermann D\"{u}rr, Joachim St\"{o}hr Understanding magnetic properties at ultrafast timescales is crucial for the development of new magnetic devices. Such devices will e.g. employ the spin torque or spin Hall effect, whose manifestation at the nanoscale is not yet sufficiently understood. Hence, addressing these effects is of great fundamental significance. X-ray microscopy at the nanoscale is an excellent tool for the study of complex magnetic devices but it is crucial to push the time resolution and sensitivity well beyond the current capabilities. For this reason we developed a microscope with a single photon counting electronics that effectively allows us to use a double lock-in detection at 476MHz (the x-ray pulse frequency) and 1.28MHz (the synchrotron revelation frequency). The sample excitation is fully synchronized with the detection as well. This setup allows us to achieve a signal to noise ratio of better than 10000, enabling us to detect miniscule variations of the x-ray absorption cross section with tens of ps of time resolution. In this talk I will describe our setup and present first results. We successfully achieved the first direct observation of so called traveling spin waves and the detection of a spin polarized current in Cu injected from an adjacent Co layer. [Preview Abstract] |
Monday, March 2, 2015 10:12AM - 10:48AM |
A27.00006: Seeing with the nano-eye: accessing structure, function, and dynamics of matter on its natural length and time scales Invited Speaker: Markus Raschke To understand and ultimately control the properties of most functional materials, from molecular soft-matter to quantum materials, requires access to the structure, coupling, and dynamics on the elementary time and length scales that define the microscopic interactions in these materials. To gain the desired nanometer spatial resolution with simultaneous spectroscopic specificity we combine scanning probe microscopy with different optical, including coherent, nonlinear, and ultrafast spectroscopies. The underlying near-field interaction mediated by the atomic-force or scanning tunneling microscope tip provides the desired deep-sub wavelength nano-focusing enabling few-nm spatial resolution. I will introduce our generalization of the approach in terms of the near-field impedance matching to a quantum system based on special optical antenna-tip designs. The resulting enhanced and qualitatively new forms of light-matter interaction enable measurements of quantum dynamics in an interacting environment or to image the electromagnetic local density of states of thermal radiation. Other applications include the inter-molecular coupling and dynamics in soft-matter hetero-structures, surface plasmon interferometry as a probe of electronic structure and dynamics in graphene, and quantum phase transitions in correlated electron materials. These examples highlight the general applicability of the new near-field microscopy approach, complementing emergent X-ray and electron imaging tools, aiming towards the ultimate goal of probing matter on its most elementary spatio-temporal level. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700