Ph.D., Physical Chemistry, University of Wisconsin-Madison, 2013
In the Laaser Lab, we are interested in developing a physical understanding of how changes at the molecular level translate to the macroscopic properties of responsive polymeric materials. For example, how does a change in charge spacing affect the interactions between charged polymers, and at what point do the polymers stop behaving like isolated chains in solution and start behaving like part of a bulk material? How do orientational changes in single polymer chains propagate through a material to achieve macroscopic ordering? And how do polymeric networks transduce force, to achieve things like mechanochemical responses?
We explore these questions by a number of optical and spectroscopic methods, such as light scattering and Raman and infrared spectroscopy, along with classical materials characterization methods like rheology and electron microscopy. Together, these methods allow us to develop new understanding of the structure and dynamic properties of responsive polymeric materials, and offer students the opportunity to gain broad experience in both physical chemistry and polymer science.
Most Cited Publications
"Adding a dimension to the infrared spectra of interfaces using heterodyne detected 2D sum-frequency generation (HD 2D SFG) spectroscopy," Wei Xiong, Jennifer E. Laaser, Randy D. Mehlenbacher, and Martin T. Zanni, PNAS 108, 20902 (2011)
"Time-Domain SFG Spectroscopy Using Mid-IR Pulse Shaping: Practical and Intrinsic Advantages," Jennifer E. Laaser, Wei Xiong, and Martin T. Zanni, J. Phys. Chem. B 115, 2536 (2011)
"Transient 2D IR Spectroscopy of Charge Injection in Dye-Sensitized Nanocrystalline Thin Films," Wei Xiong, Jennifer E. Laaser, Peerasak Paoprasert, Ryan A. Franking, Robert J. Hamers, Padma Gopalanand Martin T. Zanni, J. Am. Chem. Soc. 131,18040 (2009)
"Two-Dimensional Sum-Frequency Generation Reveals Structure and Dynamics of a Surface-Bound Peptide," Jennifer E. Laaser, David R. Skoff, Jia-Jung Ho, Yongho Joo, Arnaldo L. Serrano, Jay D. Steinkruger, Padma Gopalan, Samuel H. Gellman, and Martin T. Zanni, J. Am. Chem. Soc. 136, 95 (2014)
"Bridge-Dependent Interfacial Electron Transfer from Rhenium−Bipyridine Complexes to TiO2 Nanocrystalline Thin Films," Peerasak Paoprasert, Jennifer E. Laaser, Wei Xiong, Ryan A. Franking, Robert J. Hamers, Martin T. Zanni, J. R. Schmidt and Padma Gopalan, J. Phys. Chem. C 114, 9898 (2010)
"Charge-Density-Dominated Phase Behavior and Viscoelasticity of Polyelectrolyte Complex Coacervates," J Huang, FJ Morin, and JE Laaser. Macromolecules (2019)
"Charge Density-and Hydrophobicity-Dependent Dynamics of Polyelectrolyte Complex Coacervates," J Laaser and J Huang. APS Meeting Abstracts (2019)
"19F Magnetic Resonance Imaging of Injectable Polymeric Implants with Multiresponsive Behavior." Sedlacek, Ondrej, Daniel Jirak, Andrea Galisova, Eliezer Jager, Jennifer E. Laaser, Timothy P. Lodge, Petr Stepanek, and Martin Hruby. Chemistry of Materials 30, no. 15 (2018): 4892-4896.
"Composition-dependent dynamics in polyelectrolyte complex coacervates." Laaser, Jennifer, Frances Morin, and Jun Huang. In ABSTRACTS OF PAPERS OF THE AMERICAN CHEMICAL SOCIETY, vol. 255. 1155 16TH ST, NW, WASHINGTON, DC 20036 USA: AMER CHEMICAL SOC, 2018.
Department of Physics and Astronomy, University of Pittsburgh
Ph.D., Physics, University of Michigan, 2004
Gurudev Dutt focuses on the quantum control of condensed matter systems. Advances in material fabrication and nanotechnology have pushed modern electronic and optical devices to regimes where quantum properties of matter become important. A key feature of quantum physics is the quantum superposition principle. For a single particle, this permits the existence of a phase coherent quantum wavefunction; for two or more particles, quantum entangled wavefunctions exhibit non-classical correlations between the particles. Quantum coherence and entanglement are not only the cornerstone of modern physics, but also have become tools in the growing field of quantum information science and technology with which to realize new paradigms for secure communication, enhanced computation, and precision metrology.
While there have been a number of demonstrations of fundamental principles using isolated atoms and photons, coherent quantum control and large scale entanglement remains experimentally challenging in robust, stable condensed matter systems. The basic building blocks of these solid-state quantum systems are simple, and familiar to most physicists: single spins, photons and springs. The Dutt group is building quantum control toolboxes for thesesystems, motivated by the need for larger interconnected systems. Tools from several areas such as nuclear magnetic resonance, quantum optics, quantum information science, chemistry and nanoscience are required in this hybrid approach.
Most Cited Publications
"Nanoscale magnetic sensing with an individual electronic spin in diamond," J. R. Maze, P. L. Stanwix, J. S. Hodges, S. Hong, J. M. Taylor, P. Cappellaro, L. Jiang, M. V. Gurudev Dutt, E. Togan, A. S. Zibrov, A. Yacoby, R. L. Walsworth & M. D. Lukin, Nature 455, 644 (2008)
"Quantum Register Based on Individual Electronic and Nuclear Spin Qubits in Diamond," M. V. Gurudev Dutt, L. Childress, L. Jiang, E. Togan, J. Maze, F. Jelezko, A. S. Zibrov, P. R. Hemmer, M. D. Lukin, Science 316, 1312 (2007)
"Coherent Dynamics of Coupled Electron and Nuclear Spin Qubits in Diamond," L. Childress, M. V. Gurudev Dutt, J. M. Taylor, A. S. Zibrov, F. Jelezko, J. Wrachtrup, P. R. Hemmer, M. D. Lukin, Science 314, 281 (2006)
"Quantum entanglement between an optical photon and a solid-state spin qubit," E. Togan, Y. Chu, A. S. Trifonov, L. Jiang, J. Maze, L. Childress, M. V. G. Dutt, A. S. Sørensen, P. R. Hemmer, A. S. Zibrov & M. D. Lukin, Nature 466, 730 (2010)
"Stimulated and Spontaneous Optical Generation of Electron Spin Coherence in Charged GaAs Quantum Dots," M. V. Gurudev Dutt, Jun Cheng, Bo Li, Xiaodong Xu, Xiaoqin Li, P. R. Berman, D. G. Steel, A. S. Bracker, D. Gammon, Sophia E. Economou, Ren-Bao Liu, and L. J. Sham, Phys. Rev. Lett. 94, 227403 (2005)
"Single-photon heralded two-qubit unitary gates for pairs of nitrogen-vacancy centers in diamond." Liu, Chenxu, M. V. Dutt, and David Pekker. Physical Review A 98, no. 5 (2018).
Department of Physics and Astronomy, University of Pittsburgh
Ph.D., Chemistry, University of California Berkeley, 1985
Carrier dynamics in solid–state materials Fundamental electrical, magnetic, and optical properties of solid–state materials are determined by the dynamical response of carriers to internal and external fields. The near–equilibrium properties of carriers in most materials are well understood from classical studies of transport and optical conductivity. However, due to strong interactions of carriers among themselves and with the lattice, studies of nonequlibrium dynamics on femtosecond time scales (10 – 15 s) are just emerging. In our group, a particularly versatile and powerful technique, time–resolved two–photon photoemission (TR–2PP) spectroscopy, has been developed for studying the carrier excitation and relaxation processes in solid–state materials. With this technique we are investigating the quantum mechanical phase and carrier population relaxation times in metals, and for intrinsic and adsorbate induced surface states on metals. Of particular interest are the physical processes that induce e–h pair decoherence, since they impose limits on time scales for quantum control of carriers through the optical phase of the excitation light. The manipulation of the carrier phase with light may lead to applications such as ultrafast (>10 THz) switching and information processing, as well as, atomic manipulation of matter, and therefore, it is of great interest for advanced technologies in the 21st century. Ultrafast microscopy Understanding of the carrier dynamics under quantum confinement is a key to advancing nanoscale science and technology. Although with the existing scanning probe techniques we can potentially study dynamics of individual nanostructures, there is also a clear need for ultrafast imaging microscopic techniques in studies of dynamics in complex systems of nanostructures that could comprise ultrafast electronic or optical device. Photoemission electron microscopy (PEEM) is a well–developed surface science technique for imaging nanostructures on metal and semiconductor surfaces. In combination with femtosecond pump–probe excitation, we intend to develop time–resolved PEEM with potentially <1 fs, <20 nm, <100 meV carrier energy resolution. This technique will be applied to fundamental studies of carrier dynamics in individual nanostructures and coupled nanocomposite systems, in order to understand the fundamental physics of hot carriers in low dimensional systems and to develop advanced device concepts. Atomic manipulation with light Electronic excitation of clean or adsorbate covered metal surfaces can impulsively turn–on large mechanical forces that lead to mass transport parallel or perpendicular to the surface. When such forces are harnessed properly, they can be used for atomic manipulation or even atomic switching. Although there are now several examples of atomic manipulation with STM techniques, much less is known about how equivalent, but much larger scale manipulation could be accomplished with light. The recent observation and demonstration of quantum control of motion of Cs atoms above a Cu(111) surface by our group provides a proof–of–principle for the atomic manipulation of surfaces with light. Such studies are being extended to identify the factors that govern the electronic relaxation of adsorbates on metal surfaces, which can effectively quench the nuclear motion.
"Femtosecond imaging of surface plasmon dynamics in a nanostructured silver film," Atsushi Kubo, Ken Onda, Hrvoje Petek, Zhijun Sun, Yun S Jung, Hong Koo Kim, Nano Lett. 5, 1123 (2005)
"Real-time observation of adsorbate atom motion above a metal surface," Hrvoje Petek, Miles J Weida, Hisashi Nagano, Susumu Ogawa, Science 288, 1402 (2000)
"Wet electrons at the H2O/TiO2 (110) surface," Ken Onda, Bin Li, Jin Zhao, Kenneth D Jordan, Jinlong Yang, Hrvoje Petek, Science 308, 1154 (2005)
"Self-energy and excitonic effects in the electronic and optical properties of TiO2 crystalline phases," L Chiodo, JM Garcia-Lastra, A Iacomino, S Ossicini, J Zhao, H Petek, and A Rubio. Physical Review B 82.4 (2010)
"Plasmonic Spin-Hall Effect in Surface Plasmon Polariton Focusing," Y Dai and H Petek. ACS Photonics (2019)
Department of Physics and Astronomy, University of Pittsburgh
Ph.D., Ohio State University, 1952
We are primarily interested in the optical and electronic characterization of currently important large bandgap semiconductors such as AIN, GaN and SiC. Great emphasis in our research is placed on a close collaboration with the world`s most outstanding growers of single crystal boule material or single crystal epitaxial films. Most recently we have started to learn how to prepare and study single crystal porous SiC. Many new morphologies have been discovered in both n and p type SiC, and applications to medicine, gas sensing and fuel cells are being explored.
We study optical and electrical properties by a variety of techniques, and also put considerable effort into preparation of specialized samples. Regarding nanoscience and technology, examples of relevant work include the fabrication and investigation of porous SiC and investigations of polytype inclusions which behave as quantum wells.
We are also investigating SiC as a tool for nano-machining applications, as a substitute for diamond, towards applications for which diamond does not work well or at all.
"Determination of the phonon dispersion of zinc blende (3C) silicon carbide by inelastic x-ray scattering," J. Serrano, J.Strempfer, M. Cardona, M. Schwoerer-Böhning, H. Requardt, M. Lorenzen. B. Stojetz, P. Pavaone and W.J.Choyke, Appl. Phys. Lett. V80, 4360, (2002)
"Determination of the electric field in 4H/3C/4H quantum wells due to spontaneous polarization in the 4H SiC matrix," S. Bai, R.P. Devaty, W.J. Choyke, U. Kaiser, G. Wagner, and M.F. MacMillan, Appl. Phys. Lett. V83, 3171, (2003)
"Identification of the Carbon Dangling Bond Center at the 4H/-SiC/SiO2 Interface by an EPR Study in Oxidized Porous SiC," J.L. Cantin, H.J. von Bardeleben, Y. Shishkin, Y.Ke, R.P. Devaty and W.J.Choyke, Phys. Rev. Lett. V92, 015502-1, (2004)
"Annealing of electron irradiated, thick, ultrapure 4H SiC between 1100°c and 1500°c and measurements of lifetime and photoluminescence." Klahold, W.M., Devaty, R.P., Choyke, W.J., (...), Kimoto, T., Ohshima, T. Materials Science Forum 778-780, pp. 273-276. (2014).
Department of Electrical and Computer Engineering, Carnegie Mellon University
Ph.D., Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 1987
Towe's group pursues research in basic optical and quantum phenomena in materials for applications in novel photonic devices that enable a new generation of information processing systems for communication, computation, and sensing. The group is also interested in understanding new pathways and fundamental mechanisms for solar energy conversion devices. Current focus is on the use of phenomena (such as three-dimensional quantum-confinement effects in nanometer-scale structures) in the study of novel devices. Examples include: quantum-dot infrared detectors and imaging sensors, electrically-pumped photonic crystal micro-cavity lasers with quantum-dot active regions, multi-spectral solar energy conversion devices, plasmonic bio-sensors, and fluorescence bio-sensing devices.
"Size, shape, composition, and electronic properties of InAs/GaAs quantum dots by scanning tunneling microscopy and spectroscopy," S. Gaan, G. He, R.M. Feenstra, J Walker, and E. Towe, J. Appl. Phys. 108, 114315 (2010)
"A Unified Approach to Achieving High Power and High Energy in Chirally-coupled-core Ytterbium-doped Fiber Amplifier Systems," Bai, Jinxu & Zhang, Jim & Koponen, Joona & Kanskar, Manoj & Towe, Elias, IEEE Photonics Journal 10 (2018)
"Low-threshold voltage ultraviolet light-emitting diodes based on (Al,Ga)N metal–insulator–semiconductor structures," Liang, Yu-Han & Towe, Elias, Applied Physics Express 10 (2017)
Department of Chemistry, Carnegie Mellon University
Ph.D., Physical Chemistry, University of Chicago, 1989
We measure several fundamental electronic properties of molecules such as charge transfer and electronic delocalization using a technique known as Stark spectroscopy. Stark spectroscopy involves applying large electric fields to molecules in films or matrices and analyzing the effects of the field perturbation on the absorption or emission spectrum. We have recently focused on the properties of MEH-PPV and other molecules used to make to organic light emitting diodes (OLED's). Stark spectroscopy reveals the mechanism by which a large applied electric field, such as those present in OLEDs, produces undesirable emission quenching and suggests strategies for minimizing this loss of device efficiency through modifications of the polymer structure.
Emission properties of Single Molecules and Aggregates
Recent years has seen a huge growth in the use of organic conjugated oligomers and polymers in the design of light emitting diodes (OLEDs) and photovoltaic cells. When these molecules are placed in thin films to fabricate devices, they typically form aggregates. These confer several desirable properties for device function such as protection from oxidative damage and enhanced charge transport. However, they also typically shift the wavelength of emission to lower energies and often significantly reduce its intensity. Our group is using microscopy and spectroscopy to investigate the relationships between molecular structure and the brightness and photo-stability of molecules in the solid state, both in isolation (i.e. as single molecules) and as aggregates. We are also developing methods to image aggregation in films at high resolution and to follow the nucleation of aggregates in the solution phase.
"Effects of Solvent Properties on the Spectroscopy and Dynamics of Alkoxy-Substituted PPV Oligomer Aggregates," Woong Young So, Jiyun Hong, Janice J. Kim, Gizelle A. Sherwood, Kelly Chacon-Madrid, James H. Werner, Andrew P. Shreve, and Linda A. Peteanu, J. Phys. Chem. B 116 10504 (2012)
"Wavelength Dependence of the Fluorescence Quenching Efficiency of Nearby Dyes by Gold Nanoclusters and Nanoparticles: The Roles of Spectral Overlap and Particle Size," Chowdhury, Sanchari; Wu, Zhikun; Jaquins-Gerstl, Andrea; Liu, Shengpeng; Dembska, Anna; Armitage, Bruce A.; Jin, Rongchao; Peteanu, Linda A., J. Phys. Chem. C 115, 20105 (2011)
"Visualizing Core-Shell Structure in Substituted PPV Oligomer Aggregates Using Fluorescence Lifetime Imaging Microscopy (FLIM)," Peteanu, Linda A.; Sherwood, Gizelle A.; Werner, James H.; Shreve, Andrew P.; Smith, Timothy M.; Wildeman, Jurjen, J. Phys. Chem. C 115 15607 (2011)
"Fluorescent DNA Nanotags Featuring Covalently Attached Intercalating Dyes: Synthesis, Antibody Conjugation, and Intracellular Imaging," Stadler, Andrea L.; Delos Santos, Junriz O.; Stensrud, Elizabeth S.; Dembska, Anna; Silva, Gloria L.; Liu, Shengpeng; Shank, Nathaniel I.; Kunttas-Tatli, E.; Sobers, Courtney J.; Gramlich, Philipp M. E.; Carell, Thomas; Peteanu, Linda A.; McCartney, Brooke M.; Armitage, Bruce A., Bioconjugate Chem. 22, 1491 (2011)
"pH-Responsive Fluorescent Molecular Bottlebrushes Prepared by Atom Transfer Radical Polymerization," Nese, Alper; Lebedeva, Natalia V.; Peteanu, Linda; Sheiko, Sergei, S.; Matyjaszewski, Krzysztof, Macromolecules 44 5905 (2011)
Most Cited Publications
"Vibrationally coherent photochemistry in the femtosecond primary event of vision," Wang, Qing, Robert W. Schoenlein, Linda A. Peteanu, Richard A. Mathies, and Charles V. Shank, Science 266, no. 5184 (1994): 422-424.
"Biodegradable nanogels prepared by atom transfer radical polymerization as potential drug delivery carriers: synthesis, biodegradation, in vitro release, and bioconjugation," Oh, Jung Kwon, Daniel J. Siegwart, Hyung-il Lee, Gizelle Sherwood, Linda Peteanu, Jeffrey O. Hollinger, Kazunori Kataoka, and Krzysztof Matyjaszewski, Journal of the American Chemical Society 129, no. 18 (2007): 5939-5945.
"Light‐induced reversible formation of polymeric micelles," Lee, Hyung‐il, Wei Wu, Jung Kwon Oh, Laura Mueller, Gizelle Sherwood, Linda Peteanu, Tomasz Kowalewski, and Krzysztof Matyjaszewski, Angewandte Chemie 119, no. 14 (2007): 2505-2509.
"A Mono-Cubocotahedral Series of Gold Nanoclusters: Photoluminescense Origin, Large Enhancement, Wide Tunability and Structure-Property Correlation," Q Li, M Zhou, WY So, J Huang, M Li, DR Kauffman, M Cotlet, T Higaki, Z Shao, LA Peteanu, and R Jin. Journal of the American Chemical Society 141.13 (2019)
"WYSo SI Mechanism of Ligand-Controlled Emission in Silicon Nanoparticles," ACS Nano (2018)
"Mechanism of Ligand-Controlled Emmision in Silicon Nanoparticles." So, W.Y., Li, Q., Legaspi, C.M., (...), Jin, R., Peteanu, L.A. ACS Nano 12(7). (2018).
I am broadly interested in condensed-matter physics, but particularly in the way that electrons behave when they are subjected to extreme conditions such as ultra-low temperatures and high magnetic fields. Under such conditions, electrons can display striking collective quantum behavior such as superconductivity, fractionalization of charge, and crystallization. Currently, we are investigating phenomena such as these by studying:
The physics of low-dimensional structures, especially “van der Waals heterostructures” of two-dimensional crystals (the most familiar of which is graphene), which we build in the lab and then fashion into mesoscopic devices using nanofabrication techniques, and
A variety of methods for probing these mesoscopic devices, such as electronic transport, capacitance, tunneling spectroscopy, and shot noise.
Most Cited Publications
"Massive Dirac Fermions and Hofstadter Butterfly in a van der Waals Heterostructure," B Hunt, JD Sanchez-Yamagishi, AF Young, M Yankowitz, Brian J LeRoy, K Watanabe, T Taniguchi, P Moon, M Koshino, P Jarillo-Herrero, RC Ashoori, Science 340, 1427 (2013)
"Tunable symmetry breaking and helical edge transport in a graphene quantum spin Hall state,"A. F. Young, J. D. Sanchez-Yamagishi, B. Hunt, S. H. Choi, K. Watanabe, T. Taniguchi, R. C. Ashoori & P. Jarillo-Herrero, Nature 505, 528 (2014)
"Evidence for a Superglass State in Solid 4He," B. Hunt, E. Pratt, V. Gadagkar, M. Yamashita, A. V. Balatsky, J. C. Davis, Science 324, 632 (2009)
"Nature of the quantum metal in a two-dimensional crystalline superconductor," A. W. Tsen, B. Hunt, Y. D. Kim, Z. J. Yuan, S. Jia, R. J. Cava, J. Hone, P. Kim, C. R. Dean & A. N. Pasupathy, Nature Physics 12, 208 (2016)
"Interplay of rotational, relaxational, and shear dynamics in solid 4he," EJ Pratt, B Hunt, V Gadagkar, M Yamashita, MF Graf, AV Balatsky, and JC Davis. Science 332 (2011)
"Electron transport in multi-dimensional fuzzy graphene nanostructures," R Garg, D Gopalan, SC de la Barrera, H Hafiz, NT Nuhfer, V Viswanathan, BM Hunt, and T Cohen-Karni. Nano Letters (2019)
"Coexistence of quantum spin hall edge state and proximity-induced superconducting gap in monolayer 1T'-WTe2," F Lupke, D Waters, SC de la Barrera, M Widom, DG Mandrus, J Yan, RM Feenstra, and BM Hunt. arXiv (2019)
"Tuning Ising superconductivity with layer and spin-orbit coupling in two-dimensional transition-metal dichalcogenides." de la Barrera, Sergio C., Michael R. Sinko, Devashish P. Gopalan, Nikhil Sivadas, Kyle L. Seyler, Kenji Watanabe, Takashi Taniguchi et al. Nature Communications 9 (2018).
Ph.D., Chemical Engineering, Carnegie Mellon University, 1963
George E. Klinzing earned his B.S. degree in Chemical Engineering from the University of Pittsburgh in 1959 and was awarded a Ph.D. in Chemical Engineering from Carnegie Mellon University in 1963. He has spent his career researching materials processing, specifically pneumatic conveying. Administrative interests revolve around fostering an environment of collaboration, support, and encouragement for research faculty, staff, and students. Activities include yearly trips with faculty to visit federal agency officials in Washington, D.C.; counseling researchers in their innovation commercialization efforts; and overseeing policy initiatives aimed at creating fair and equitable collaboration among Pitt researchers, industry, and government. He has given over 200 technical presentations at professional meetings, universities, and industries both nationally and internationally, and has advised 25 Ph.D. students and 54 M.S. students.
Most Cited Publications
"Pneumatic conveying of solids: a theoretical and practical approach," Klinzing, George E., Farid Rizk, R. Marcus, and L. S. Leung, Vol. 8. (2011).
Department of Electrical and Computer Engineering, University of Pittsburgh
Ph.D., Electrical and Computer Engineering, Carnegie Mellon University, 1989
The Kim group’s research has been centered on developing new photonic and electronic devices at micro and nanoscales involving various functional materials such as rare-earth doped oxides, wide bandgap semiconductors, ferroelectric films, and plasmonic nanostructured materials.
Their research in the nanotechnology area investigates multiscale vertical integration of nanostructures into hierarchical systems. Single-domain ordered nanochannel arrays with controlled symmetry have been developed on macroscale area of wafer surface using a directed self-organization method, and have been investigated as an interaction medium in optical, electrical, chemical, and biological domains. Surface-plasmon phenomena occurring in nano-optic structures are of particular interest, since many novel properties can be derived from those and can be incorporated into an on-chip configuration for interaction with other functional materials.
The Kim group investigates plasmonics as an enabling technology for implementing nanosystems-on-a-chip that offer multifunctionality across the heterogeneous domains.
The Pittsburgh Quantum Institute was established in 2012 to help unify and promote research in quantum science and engineering in the Pittsburgh area. PQI members have faculty appointments from Carnegie Mellon University, Duquesne University, and the University of Pittsburgh in physics, chemistry, and engineering disciplines.