Research describing how an optical field can modify the electronic properties of a solid was recently published in Nature Communications titled "Coherent multidimensional photoelectron spectroscopy of ultrafast quasiparticle dressing by light", coauthored by Dr. Marcel Reutzel, Hrvoje Petek, and Petek's students Andi Li and Zehua Wang.
Applying intense ultrafast light pulses, which provide a time-periodic electronic potential acting together with the lattice ions, defines the forces experienced by electrons in solids, such as metals and semiconductors, Petek and his coworkers demonstrated that an optical field can transiently, on the 10-14 second time scale, modify (dress) the electronic bands in a metal, potentially changing them from an electron to a hole condition. ... Continue reading
A research team led by professors from the University of Pittsburgh Department of Physics and Astronomy has announced the discovery of a new electronic state of matter. PQI members Jeremy Levy, Patrick Irvin, David Pekker, and Roger Mong are coauthors of the paper "Pascal conductance series in ballistic one-dimensional LaAIO3/SrTiO3 channels." The research focuses on measurements in one-dimensional conducting systems where electrons are found to travel without scattering in groups of two or more at a time, rather than individually. The study was published in Science on Feb. 14. Jeremy also breaks down the scientific concepts and guides the readers through their research in the following video. ... Continue reading
New research from the Giannis (Yanni) Mpourmpakis and his team introduces the first universal adsorption model that accounts for detailed nanoparticle structural characteristics, metal composition and different adsorbates, making it possible to not only predict adsorption behavior on any metal nanoparticles but screen their stability, as well. The research combines computational chemistry modeling with machine learning to fit a large number of data and accurately predict adsorption trends on nanoparticles that have not previously been seen. By connecting adsorption with the stability of nanoparticles, nanoparticles can now be optimized in terms of their synthetic accessibility and application property behavior. This improvement will significantly accelerate nanomaterials design and avoid trial and error experimentation in the lab. Their work was published in Science Advances on Sept. 13, 2019.Continue reading
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.
Read more here. ... Continue reading
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
We are a newly established group at UCLA led by Prof. Clarice D. Aiello. Our mission is to establish the extent to which quantum mechanics accounts for biologically relevant phenomena, and can be manipulated to technological and therapeutic advantage.
Experiments suggest that nontrivial quantum mechanical effects involving spin might underlie biologically relevant phenomena as varied as magnetic field detection for animal navigation, metabolic regulation in cells and optimal... Read More
Deadline: Wednesday, June 16, 2021
Congratulations to the 2020/2021 PQI Graduate Student Research Award Winners!!
Xiaowei Bogetti (Saxena Group, Chemistry), Supriya Ghosh (Waldeck Group, Chemistry), Xun Li (Lee Group, MechE), Zehan Li (Liu Group, Physics), Aditi Nethwewala (Levy Group, Physics), and Timothy Yang (Saidi Group, MechE) each won one term of graduate funding for the year 2020/2021.
Light travels at a velocity of 300 nm/fs, and nothing travels faster than that, so you will never be able to take a snapshot, as you might like, of it interacting with matter. But if you overlap two light identical pulses, their in-phase fields will add, and out-of-phase fields will subtract, causing the light intensity to be modulated on the wavelength scale and thereby allowing light fields to be imaged by a nonlinear process.
Hrvoje Petek and his group have developed a method to image light on the nanofemto scale by interferometric time-resolved photoemission electron microscopy and recently published a review article on this work in Chemical Reviews.
James McKone, Assistant Professor in the Department of Chemical and Petroleum Engineering at the University of Pittsburgh, was selected as one of the ten 2020 Beckman Young Investigator awardees. The awardees exemplify the Foundation’s mission of supporting the most promising young faculty members in the early stages of their academic careers in the chemical and life sciences, particularly to foster the invention of methods, instruments, and materials that will open new avenues of research in science.
His research focuses on designing a new generation of enzyme-like catalysts that use renewable electricity to recycle carbon dioxide emissions back into useful fuels and chemicals.
“Over the last several decades, the cost of renewable electricity has dramatically decreased to the point where building a new solar or wind farm is, in many cases, more economical than continuing to run a coal-fired power plant,” said McKone.
