How to Dress a Metal

  • By Jenny Stein
  • 6 May 2020

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. 

Move aside sliced bread, we've got a new phase of matter

  • By Jenny Stein
  • 18 February 2020

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.

First Universal Computer Model for Metal Nanoparticle Adsorption

  • By Ke Xu
  • 16 September 2019

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.

Latest research from Jeremy Levy Lab: Over 100-THz bandwidth selective difference frequency generation at LaAlO3/SrTiO3 nanojunctions

  • By Huiling Shao
  • 19 March 2019

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

Jeremy Levy named American Association for Advancement of Science (AAAS) Fellow

  • By Ke Xu
  • 30 November 2018

American Association for Advancement of Science (AAAS) has appointed Jeremy Levy as member of its 2018 lifetime fellowship cohort. AAAS will recognize the award during its annual meeting on February 16, 2019. 

Levy’s research centers around the field of oxide nanoelectronics, quantum computation, quantum transport and nanoscale optics, semiconductor and oxide spintronics, and dynamical phenomena in oxide materials and films. 

Levy will join a list of distinguished scientists including inventor Thomas Edison, astronomer Maria Mitchell and computer scientist Grace Hopper.

Single-shot condensation of exciton polaritons and the hole burning effect

  • By Leena Aggarwal
  • 10 September 2018

The single-shot measurements offer a unique opportunity to study fundamental properties of non-equilibrium condensation in the presence of a reservoir. David Snoke and his colleagues have recently reported an insight into spontaneous condensation by imaging long-lifetime exciton polaritons in a high-quality inorganic microcavity in a single-shot optical excitation regime, without averaging over multiple condensate realisations. The results are published in the Journal of Nature Communications. They have demonstrated that how condensation is strongly influenced by an incoherent reservoir and that the reservoir depletion, the so-called spatial hole burning, is critical for the transition to the ground state.

Ultrafast Microscopy of Spin-Momentum Locked Surface Plasmon Polaritons

  • By Leena Aggarwal
  • 27 June 2018

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.



Large enhancement of response times of a protein conformational switch by computational design

  • By Leena Aggarwal
  • 16 April 2018

Lillian Chong and her colleagues have recently reported, in the Journal of Nature Communications, a computational design strategy in synergistic combination with biophysical experiments to rationally improve the response time of an engineered protein-based Ca2+-sensor in which the switching process occurs via mutually exclusive folding of two alternate frames. This strategy identifies mutations that increase switching rates by as much as 32-fold, achieving response times on the order of fast physiological Ca2+ fluctuations. This computational design strategy is general and may aid in optimizing the kinetics of other protein conformational switches.

Critical heat flux enhancement in pool boiling through increased rewetting on nanopillar array surfaces

  • By Leena Aggarwal
  • 12 April 2018

Boiling is a key heat transfer process for a variety of power generation and thermal management technologies. The enhancement in both the critical heat flux (CHF) and the critical temperature at CHF of the substrate and effectively increase the limit of boiling before the boiling crisis is triggered. By using only nanopillars with a systematic variation in height and well-defined geometrical dimensions, Paul W. Leu and colleagues have established a direct link between the enhancement in capillary force and the boiling performance of a substrate. This provides new insights about design of surface textures not only to amplify the heat flux, but also to achieve an enhancement in the temperature at critical heat flux. These results are published in Scientific Reports.

Size, Shape, and Composition-Dependent Model for Metal Nanoparticle Stability Prediction

  • By Leena Aggarwal
  • 4 April 2018

Giannis Mpourmpakis and his students have proposed a bond-centric (BC) model able to capture cohesive energy trends over a range of monometallic and bimetallic nanoparticles and mixing behavior (excess energy) of nanoalloys, in great agreement with DFT calculations. This model utilizes to calculate the energetics of any nanoparticle morphology and chemical composition, thus significantly accelerating nanoalloys design. This work introduces a simple yet very powerful tool for nanoalloy design that can potentially help elucidate the energetics of alloy MNP genomes.