The ability to combine continuously tunable narrow-band terahertz (THz) generation that can access both the far-infrared and mid-infrared regimes with nanometer-scale spatial resolution is highly promising for identifying underlying light-matter interactions and realizing selective control of rotational or vibrational resonances in nanoparticles or molecules. Here, we report selective difference frequency generation with over 100 THz bandwidth via femtosecond optical pulse shaping. The THz emission is generated at nanoscale junctions at the interface of LaAlO3/SrTiO3 (LAO/STO) that is defined by conductive atomic force microscope lithography, with the potential to perform THz spectroscopy on individual nanoparticles or molecules. Numerical simulation of the time-domain signal facilitates the identification of components that contribute to the THz generation. This ultra-wide-bandwidth tunable nanoscale coherent THz source transforms the LAO/STO interface into a promising platform for integrated lab-on-chip optoelectronic devices with various functionalities.
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The recently published paper in journal of ACS NANO on Ultrafast Microscopy of Spin-Momentum Locked Surface Plasmon Polaritons is an essential research for designing optical elements to control spin-polarized SPP (surface plasmon polaritons) fields on the nano femto scale. Hrvoje Petek and his colleagues have shown two-photon photoemission electron microscopy images formed by coupling and propagation of longitudinal and transverse components of SPP fields of light. Further, they have also shown the spin-momentum locked SPP wave packets launched with circularly polarized excitation propagate at the same phase and group velocities as for the linearly polarized excitation using time-resolved experiments.Continue reading
Michael Widom and his colleagues showed what happens at the grain boundaries of one particular alloy of the metals nickel and bismuth that makes it brittle in their paper published in Science. Using advanced electron microscopes, Widom’s collaborators at Lehigh University scrutinized these microscopic grain boundaries at an atomic level. In a "very heroic experimental program" they discovered that when grains met, the bismuth and nickel atoms realigned into lattices to form layered superstructures at the grain boundaries. These superstructures had previously been thought to exist only rarely in some alloys. Finding it at many different boundaries led the team to conclude that these superstructures are probably much more common than many people had thought. Continue reading
Owing to high surface to volume ratios and chemical potential, nanoparticles possess unique optical, electrical, and thermal properties, which constitute the basis of novel applications in sensing, catalysis, nanoelectronics, bio-tagging etc. Despite the great advances in the synthesis, the total structure determination of nanoclusters still remains to be a major challenge. Recently Hyung J. Kim and their colleagues have reported the synthesis and crystal structure of a nanocluster composed of 23 silver atoms capped by 8 phosphine and 18 phenylethanethiolate ligands in the journal of Nature Communications.Continue reading
In the recently published paper in Scientific Reports, Sara A. Majetich and their colleagues have demonstrated the engineering of spin canting across a Magnetic nanoparticles (MNP) via the Dzyaloshinskii-Moriya interaction (DMI). In this paper, they have shown that strong DMI can lead to magnetic frustration within the shell and cause canting of the net particle moment. These results have illuminated how core/shell nanoparticle systems can be engineered for spin canting across the whole of the particle, rather than solely at the surface.
In the recently accepted paper in Physical Review Letter, Hrvoje Petek and his colleagues investigate the coherent electron transfer from an interface state that forms upon chemisorption of Ag nanoclusters onto graphite to a σ symmetry interlayer band of graphite. Interfacial charge transfer is a fundamental process in heterogeneous and plasmonically enhanced catalysis. The charge transfer, however, is thought to be restrained by an interfacial potential barrier, such as a Schottky barrier at a metal-semiconductor interface. With optical excitation, the interfacial charge transfer can also be efficiently completed by coherent dipole coupling between the donor and acceptor bands. In this study Petek and his colleagues advance the time-resolved multidimensional multiphoton photoemission spectroscopy technique to not only pump the donor band and probe the acceptor band, but also directly image the coherent polarization dynamics between them. They discover a direct resonant ... Continue reading
Geoff Hutchison is the 2018 Tina and David Bellet Excellence Awardee. The award recognizes his effectiveness and his innovations in teaching. Among many innovations Hutchinson developed Avagadro molecular editor; with that software, he designed projects hat allow Physical Chemistry students to perform quantum mechanical calculations to visualize results/concepts. Continue reading
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Quantum information science (QIS)—the ability to exploit intricate quantum mechanical phenomena to create fundamentally new ways of obtaining and processing information—is at the threshold of a revolution. The rapid progress in this field promises profound... Read More
Deadline: Friday, July 5, 2019
Congratulations to the 2018/2019 PQI Graduate Student Research Award Winners!
Ilia Kevlishvili (Liu Lab, Chemistry), Tzu-Chiao Chien (Hatridge Lab, Physics), Shiv Upadhyay (Jordan Lab, Chemistry), Jierui Liang (Fullerton Lab, Chemical Engineering), Caleb Clever (Waldeck Lab, Chemistry), and Zhi Li (Mong Lab, Physics) each won one term of graduate funding for the year 2019/2020.
In 2014, in the midst of a multiyear spike in helium prices, the University of Pittsburgh poured millions of dollars into building a high-tech machine aimed at recovering the helium that its researchers used. Prices stabilized soon after, and a substantial return on its investment seemed a far-off possibility. But now, as another shortage threatens the viability of basic science research, Pitt’s machine — one of the most efficient of its kind in the world — is paying dividends. Crude helium prices sold at the U.S. Bureau of Land Management’s 2019 auction clocked in at $279.95 per million standard cubic feet, an increase of roughly 135% from the year prior.
Helium is used to maintain low-operating temperatures of medical devices such as MRI scanners and nuclear magnetic resonance spectrometers — machines that help with analysis of small molecules. Mr. Chambers, the Pitt facilities director, said the university’s recovery system has decreased its helium usage by over 60%. Yet he still remains concerned about availability, especially after an ominous call from a supplier recently warning of a “large shortage” coming in July.
CMU Associate Professor of Physics Di Xiao has been awarded a fellowship by the Simons Foundation. The Simons Foundation was founded in 1994 to support research in mathematics and the basic sciences. Xiao was one of nine theoretical physicists awarded fellowships by the foundation this year. The fellowship will allow Xiao to take a sabbatical from teaching for the 2019-20 academic year to focus on his research in quantum condensed matter theory on the magnetic and electric multipoles in crystalline solids.
