Research

Thomas Killian’s research group studies ultracold neutral plasmas and quantum degenerate atomic atomic gases. Both experiments start with laser-cooled and trapped neutral strontium. Laser-cooling is a powerful technique for producing and trapping atoms at temperatures as low as one millionth of a degree above absolute zero. Under these exotic conditions, matter behaves in fundamentally different ways, and the exploration of this regime teaches us about the basic laws of nature and lays the foundation for powerful new technological advances.

Our current focus is on creating and understanding strongly interacting, many-body systems. This is a grand challenge for many areas of physics, such as in quark-gluon plasmas in high energy and nuclear physics, and a rich spectrum of phenomena in condensed matter physics including high temperature superconductivity, exotic magnetic behavior, and superfluid helium. In the quantum realm, the highly entangled wavefunctions in these systems lead to the emergence of new physics, such as superconductivity. Ultacold atoms can reach this regime when they are cooled to temperatures on the order of nanokelvin and trapped in periodic potentials called optical lattices. Exciting atoms in a BEC to Rydberg states introduces new physics because of strong, long-range interactions between Rydberg atoms. These are the directions we are pursuing with our quantum degenerate strontium experiments. Ultracold neutral plasmas are strongly interacting because their thermal energy is less than the Coulomb energy between neighboring particles. This reverses the normal energy hierarchy found in plasmas and makes theoretical description much more difficult.

We also support the development of new techniques for manipulating biological structures with electromagnetic fields. The primary application is improved cell culturing for basic life science research, personalized medicine, drug discovery, and toxicity testing. More information can be found at n3dbio.com.


Ultracold Neutral Plasmas

Over 99% of the visible matter in the universe exists as plasma, in which neutral atoms have been ionized to produce free electrons and ions. Traditionally, neutral plasmas are relatively hot, such as the solar corona (1,000,000 K), a candle flame (1000 K), or the ionosphere around our planet (300 K). Using techniques of laser cooling, which originated in the atomic physics community, it is now possible to create ultracold neutral plasmas at temperatures as low as about 1 K. In a table-top apparatus, laser light traps and cools about 1 billion neutral atoms to a thousandth of a degree above absolute zero. A second laser illuminates the cloud with photons with barely enough energy to ionize the atoms and create the plasma.

Little is known about plasmas in this new regime, and they are difficult to describe theoretically because they are strongly interacting, which means that interactions cannot be treated as a small perturbation. We are currently measuring the collision rate in these systems, which is an unsolved problem that is important for modeling dense plasmas in thermonuclear devices and the cores of gas giant planets. We also recently developed a new technique for sculpting the density distribution of the plasma, which allows us to excite ion acoustic waves and create streaming plasmas and shock waves. This represents a new direction in the study of ultracold neutral plasmas that will allow us to probe basic plasma physics phenomena with unprecedented precision.

  • Publications
  • "Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma," T.S. Strickler, T.K. Langin, P. McQuillen, J. Daligault, and T.C. Killian, Phys. Rev X 6, 021021 (2016).

    "Demonstrating universal scaling for dynamics of Yukawa one-component plasmas after an interaction quench," T.K Langin, T.Strickler, N. Maksimovic, P. McQuillen, T. Pohl, D. Vrinceanu, and T. C. Killian, Phys. Rev. E. 93, 023201 (2016).

    Editor's Suggestion

    "Ion Temperature Evolution in an Ultracold Neutral Plasma," P. McQuillen, T. Strickler, T. Langin, and T. C. Killian, Phys. Plasmas 22, 033513 (2015).

    "Emergence of Kinetic Behavior in Streaming Ultracold Neutral Plasmas," P. McQuillen, J. Castro, S. J. Bradshaw, and T. C. Killian, Phys. Plasmas 22, 043514 (2015).

    "Strongly Coupled Plasmas via Rydberg-Blockade of Cold Atoms," G. Bannasch, T. C. Killian, and T. Pohl, Phys. Rev. Lett. 110, 253003 (2013).

    "Ion Holes in the Hydrodynamic Regime in Ultracold Neutral Plasmas," P. McQuillen, J. Castro, T. Strickler, S. J. Bradshaw, and T. C. Killian, Phys. Plasmas 20, 043516 (2013).

    "Imaging the Evolution of an Ultracold Strontium Rydberg Gas," P. McQuillen, X. Zhang, T. Strickler, F. B. Dunning, and T. C. Killian, Phys. Rev. A. 87, 013407 (2013).

    "Velocity Relaxation in a Strongly Coupled Plasma," G. Bannasch, J. Castro, P. McQuillen, T. Pohl, and T. C. Killian, Phys. Rev. Lett. 109, 185008 (2012).

    "Creating and Studying Ion Acoustic Waves in Ultracold Neutral Plasmas," T. C. Killian, P. McQuillen, T. O'Neil and J. Castro, Phys. Plasmas 19, 055701 (2012).

    "Creating Non-Maxwellian Velocity Distributions in Ultracold Plasmas," J. Castro, G. Bannasch, P. McQuillen, T. Pohl and T. C. Killian, AIP Conf. Proc. 1421, 31 (2011).

    "High-Resolution Ionization of Ultracold Neutral Plasmas," P. McQuillen, J. Castro, and T.C. Killian, J. Phys. B. 44, 184013 (2011).

    "Ion Acoustic Waves in Ultracold Neutral Plasmas," J. Castro, P. McQuillen, and T.C. Killian, Phys. Rev. Lett. 105, 065004 (2010).

    "Ultracold Neutral Plasmas," T.C. Killian and S. L Rolston, Phys. Today 63, 46 (2010).

    "Using Sheet Fluorescence to Probe Ion Dynamics in Ultracold Neutral Plasmas." J. Castro, H. Gao, and T. C. Killian, Plasma Phys. Control. Fusion 50, 124011 (2008).

    "Optical Probes of Ultracold Neutral Plasmas," S. Laha, J. Castro, H. Gao, P. Gupta, C.E. Simien, and T. C. Killian, AIP Conf. Proc. 926, 69 (2007).

    "Ultracold Neutral Plasmas", T. C. Killian, T. Pattard, Thomas Pohl, and J. M. Rost, Phys. Rep. 449, 77 (2007).

    "Ultracold Neutral Plasmas", Thomas C. Killian, Science 316, 705 (2007).

    "Optical Probes of Ultracold Neutral Plasmas," CP926, Atomic Processes in Plasmas­--15th International Conference on Atomic Process in Plasmas, edited by J.D. Gillaspy, J.J. Curry, and W.L. Wiese (2007).

    "Experimental Realization of an Exact Solution to the Vlasov Equations for an Expanding Plasma," S. Laha, P. Gupta, C.E. Simien, H. Gao, J. Castro, T. Pohl, and T. C. Killian, Phys. Rev. Lett. 99, 155001 (2007).

    "Electron Temperature Evolution in Expanding Ultracold Neutral Plasmas," P. Gupta, S. Laha, C.E. Simien, H. Gao, J. Castro, T. C. Killian, and T. Pohl, Phys. Rev. Lett. 99, 075005 (2007).

    "Kinetic Energy Oscillations in Annular Regions of Ultracold Neutral Plasmas," S. Laha, Y. C. Chen, P. Gupta, C.E. Simien, Y.N. Martinez, P.G. Mickelson, S.B. Nagel, and T.C. Killian, Eur. Phys. J. D 40, 51 (2006).

    "Absorption Imaging and Spectroscopy of Ultracold Neutral Plasmas," T. C. Killian, Y. C. Chen, P. Gupta, S. Laha, Y. N. Martinez, P. G. Mickelson, S. B. Nagel , A. D. Saenz, and C. E. Simien, J. Phys. B, 38, 351 (2005).

    Electron Screening and Kinetic Energy Oscillations in a Strongly Coupled Plasma," Y.C. Chen, C.E. Simien, P. Gupta, S. Laha, Y.N. Martinez, P.G. Mickelson, S.B. Nagel, and T.C. Killian, Phys. Rev. Lett. 93, 265003 (2004).

    "Using Absorption Imaging to Study Iron Dynamics in an Ultracold Neutral Plasma," C. E. Simien, Y. C. Chen, P. Gupta, S. Laha, Y. N. Martinez, P. G. Mickelson, S. B. Nagel, and T. C. Killian, Phys. Rev. Lett. 92, 143001 (2004).

    "Plasmas Put in Order," T.C. Killian, Nature 429, 815 (2004).


  • Theses
  • "Universality in the Equilibration of Quenched Yukawa One Component Plasmas." Master thesis by Thomas Langin (2015).

    "High Resolution Measurement and Modeling of Ion Dynamics in an Ultracold Neutral Plasma." Doctoral thesis by Patrick McQuillen (2015). .

    "High Resolution Sculpting and Imaging of Ultracold Neutral Plasmas." Master thesis by Patrick McQuillen (2012).

    "Collective effects in Ultracold Neutral Plasmas." Doctoral thesis by Jose Castro (2011). Corrected spectral integral formula (Strickler, 2014).

    "Sheet Fluorescence and Annular Analysis of Ultracold Neutral Plasmas" Master thesis by Jose Castro (2009).

    "Early Time Ion Dynamics and Progress Towards Laser Cooling in an Ultracold Neutral Plasma Doctoral thesis by Clayton Simien (2007).

    "Ion Dynamics in Strongly Coupled Plasmas" Doctoral thesis by Sampad Laha (2007).

    "Expansion and Electron Temperature Evolution in an Ultracold Neutral Plasma" Doctoral thesis by Priya Gupta (2007).

    "Kinetic Energy Oscillations in Annular Regions of an Ultracold Neutral Plasma" Master thesis by Sampad Laha (2005).

    "Pulsed Dye Laser for Excitation of Strontium" Master thesis by Priya Gupta (2004).

    "422 nm Laser" Master thesis by Clayton Simien (2004).

    Quantum Degenerate Atomic Strontium: Rydberg Atoms, Lattices, and More

    Our work on ultracold neutral atomic strontium focuses on the study of quantum degenerate gases. When atoms are cooled down to temperatures on the order of a millionth of a degree above absolute zero, they enter a regime dominated by quantum mechanics in which we can search for new phenomena and explore novel states of matter, or study the underlying physics of magnetism and superconductivity. Ultracold atoms serve as ideal model systems because the individual particles are well characterized, and their interactions can be controlled in ways that are not possible with traditional materials. Strontium in particular, has two valence electrons, which is unlike most other elements that have been coaxed into the quantum degenerate regime, and this has been predicted to lead to new types of collective properties at ultracold temperatures. In 2009 and 2010, we created the first strontium Bose-Einstein condensates and quantum degenerate Fermi gases, and we are currently developing new ways to control the interactions between atoms using laser light and putting atoms into optical lattices to access the strongly interacting regime. Atoms can also be promoted to highly excited Rydberg states, which interact with each other with strong, long-range forces due to the large dipole moments possible in these states. Dipolar interactions are predicted to lead to exotic phenomena such as supersolidity and three-dimensional solitons. Strontium has many advantages for these experiments.

  • Publications
  • "Resonant Rydberg Dressing of Alkaline-Earth Atoms via Electromagnetically Induced Transparency," C. Gaul, B.J. DeSalvo, J.A. Aman, F.B. Dunning, T.C. Killian, and T. Pohl, Phys. Rev. Lett. 116, 243001 (2016).

    Editor's Suggestion

    "Trap losses induced by near-resonant Rydberg dressing of cold atomic gases," J. A. Aman, B. J. DeSalvo, F. B. Dunning, T. C. Killian, S. Yoshida, and J. Burgdörfer, Phys. Rev. A. 93, 043426 (2016).

    "Rydberg-blockade effects in Autler-Townes spectra of ultracold strontium," B. J. DeSalvo, J. A. Aman, C. Gaul, T. Pohl, S. Yoshida, J. Burgdörfer, K. R. A. Hazzard, F. B. Dunning, and T. C. Killian, Phys. Rev. A. 93, 022709 (2016).

    "Ultra-long-range Rydberg molecules in a divalent atomic system," B. J. DeSalvo, J. A. Aman, F. B. Dunning, T. C. Killian, H. R. Sadeghpour, S. Yoshida, and J. Burgdörfer, Phys. Rev. A. 92, 031403(R) (2015).

    "Production of very-high-n strontium Rydberg atoms," S. Ye, X. Zhang, T. C. Killian, F. B. Dunning, M. Hiller, S. Yoshida, S. Nagele, J. Burgdorfer, Phys. Rev. A 88, 043430 (2013).

    "Rabi Oscillations between Atomic and Molecular Condensates Driven with Coherent One-Color Photoassociation," Mi Yan, B. J. DeSalvo, Y. Huang, P. Naidon, and T. C. Killian, Phys. Rev. Lett. 111, 150402 (2013).

    Editor's Suggestion

    "Degenerate Quantum Gases of Strontium," S. Stellmer, F. Schreck, and T. C. Killian, submitted Annual Review of Cold Atoms and Molecules, vol. 2. Ed. by K. W. Madison, Y. Wang, A. M. Rey, and K. Bongs, arxiv.org/1307.0601 (2013).

    "Controlling Condensate Collapse and Expansion with an Optical Feshbach Resonance," M. Yan, B. J. DeSalvo, B. Ramachandhran, H. Pu, and T. C. Killian, Phys. Rev. Lett. 110, 123201 (2013).

    "Numerical Modeling of Collisional Dynamics of Sr in an Optical Dipole Trap," M. Yan, R. Chakraborty, A. Mazurenko, P. G. Mickelson, Y. N. Martinez de Escobar, B. J. DeSalvo, and T. C. Killian , Phys. Rev. A 83, 032705 (2011).

    "Degerate Fermi Gas of 87-Sr," B. J. DeSalvo, M. Yan, P. G. Mickelson, Y. N. Martinez de Escobar, and T.C. Killian, Phys. Rev. Lett. 105, 030402 (2010).

    Editor's Suggestion

    "Bose-Eistein Condensation of 88-Sr Through Sympathetic Colling with 87-Sr," P.G. Mickelson, Y. N. Martinez de Escobar, M. Yan, B. J. DeSalvo, and T. C. Killian, Phys. Rev. A 81, 051601 (R) (2010).

    "Bose-Einstein Condensation of 84-Sr," Y. N. Martinez de Escobar, P. G. Mickelson, M. Yan, B. J. DeSalvo, S. B. Nagel and T. C. Killian, Phys. Rev. Lett. 103, 200402 (2009).
    Featured in Physics, Physics World, e! Science News, Nanotechwire, and Rice News.

    Physics Viewpoint Editor's Suggestion

    "Repumping and Spectroscopy of Laser-cooled Sr Atoms Using the (5s5p)3P2 - (5s4d)3D2transition," P. G. Mickelson, Y. N. Martinez de Escobar, P. Anzel, B. J. DeSalvo, S. B. Nagel, A. J. Traverso, M. Yan, T. C. Killian, J. Phys. B 42, 235001, (2009).

    "Inelastic and Elastic Collision Rates for Triplet States of Ultracold Strontium," A. Traverso, R. Chakraborty, Y. N. Martinez de Escobar, P. G. Mickelson, S. B. Nagel, M. Yan, and T. C. Killian, Phys. Rev. A 79, 060702 (R) (2009).

    "Two-Photon Photoassociative Spectroscopy of Ultracold 88-Sr," Y. N. Martinez de Escobar, P. G. Mickelson, P. Pellegrini, S. B. Nagel, A. Traverso, M. Yan, R. Cote, and T. C. Killian, Phys. Rev. A 78, 062708 (2008).

    "Modification of Atom Scattering Using an Intercombination-line Optical Feshbach Resonance at Large Detuning," Y. N. Martinez de Escobar, P. G. Mickelson, M. Yan, and T. C. Killian, arXiv:0906.1837 (2009).

    "Pumped Quantum Systems: Immersion Fluids of the Future?" Vikas Anant, Magnus Raadmark, Ayman F. Abouraddy, Thomas C. Killian, Karl K. Berggren, physics/0509228

    "Spectroscopic Determination of the s-Wave Scattering Lengths of 86-Sr and 88-Sr," P. G. Mickelson, Y. N. Martinez, A. D. Saenz, S. B. Nagel, Y. C. Chen, T. C. Killian, P. Pellegrini, and R. Cote, Phys. Rev. Lett. 95, 223002 (2005).

    "Photoassociatie Spectroscopy at Long Range in Ultracold Strontium," S. B. Nagel, P. G. Mickelson, A. D. Saenz, Y. N. Martinez, Y. C. Chen, T. C. Killian, P. Pellegrini, and R. Cote, Phys. Rev. Lett. 94, 083004 (2005).

    "Magnetic Trapping of Metastable 3P2 Atomic Strontium," S. B. Nagel, C. E. Simien, S. Laha, P. Gupta, V. S. Ashoka, and T. C. Killian, Phys. Rev. A 67, 011401 (2003).


  • Theses
  • "Strontium Laser Cooling and Trapping Apparatus" Master thesis by Francisco Camargo (2015).

    "Ultralong-Range Molecules and Rydberg Blockade in Ultracold 84-Sr" Doctoral thesis by Brian DeSalvo (2015).

    "Optical Feshbach Resonances and Coherent Photoassociation in a Strontium BEC" Doctoral thesis by Mi Yan (2013).

    "A New Optical Trap System for Ultracold Strontium" Master thesis by Ying Huang (2013).

    "Degenerate Fermi Gas of 87-Sr" Master thesis by Brian DeSalvo (2013).

    "Numerical modeling of collisional dynamics of Sr in an optical dipole trap" Master thesis by Mi Yan (2011).

    "Bose-Einstein Condensation of 84-Sr" Doctoral thesis by Yenny Natali Martinez de Escobar (2010).

    "Trapping and Evaporation of 87-Sr and 88-Sr Mixtures" Doctoral thesis by Pascal Mickelson (2010).

    "Ultracold Collisions in Atomic Strontium" Doctoral thesis by Sarah Nagel (2008).

    "Saturation Effects in Photoassociation Spectroscopy of 86Sr" Master thesis by Pascal Mickelson (2006).

    "Studies of the 5s2 1S0 - 5s5p 3P1 Transition in Atomic Strontium" Master thesis by Natali Martinez (2008).

    "A Narrow Linewidth Diode Laser System for Strontium Laser Cooling Applications" Master thesis by Sarah Nagel (2004).

    "461 nm Laser For Studies In Ultracold Neutral Strontium" Master thesis by Aaron Saenz (2005).

    Manipulating Biological Systems with Electric and Magnetic Fields

    In collaboration with Robert Raphael in Bioengineering and Biotech startup n3D Biosciences, Inc. ( n3dbio.com), we are developing new techniques to manipulate cells and probe cell membranes with electromagnetic fields. A recent discovery is being commercialized by n3D as a new technology for levitating cells off the flat, two-dimensional surface of a petri dish and allowing them to grow in three dimensions. Three-dimensional structure and interactions with surrounding tissue, as experienced by cells in the body, are critical for normal cell growth and function. So this new technology has great potential for basic bio-medical research, drug discovery, and tissue engineering.

  • Publications
  • "A high-throughput three-dimensional cell migration assay for toxicity screening with mobile device-based macroscopic image analysis," David M. Timm, M. S., Jianbo Chen, B. S., David Sing, B. S., Jacob A. Gage, B. S., William L. Haisler, B. S., Shane K. Neeley, B. A., Robert M. Raphael, Ph. D., Mehdi Dehghani, Ph. D., Kevin P. Rosenblatt, M. D. Ph. D., T. C. Killian, Hubert Tseng, and Glauco R. Souza, Scientific Reports 3, 3000 (2013).

    "Three- dimensional cell culturing by magnetic levitation," William L. Haisler, David M. Timm, Jacob A. Gage, Hubert Tseng, T. C. Killian, Glauco R. Souza, Nature Protocals 8, 1940 (2013).

    "Assembly of a Three-dimensional Multi-type Bronchiole Co-culture Model Using Magnetic Levitation," H. Tseng, J. A. Gage, R. M. Raphael, R. H. Moore, T.C. Killian, K. J. Grande-Allen, and G. R. Souza, Tissue Eng. Part C: Methods 19, 665 (2013).

    "A Microfabricated Magnetic Force Transducer-Microaspiration System for Studying Membrane Mechanics," D.J. Stark, T.C. Killian, and R. M. Raphael, Phys. Biol. 8, 056008 (2011).

    "Three-dimensional Tissue Culture Based on Magnetic Cell Levitation," G. R. Souza, J. R Molina, R. M. Raphael, M. G. Ozawa, D. J. Stark, C. S. Levin, L. F. Bonk, J. S. Ananta, J. Mandelin,M.M. Georgescu, J. A. Bankson, J. G. Gelovani, T. C. Killian, R. Pasqualini, and W. Arap, Nature Nanotech. 5, 291 (2010).

    "High-throughput non-viral gene transfer by mRNA electroporation to generate CD19-specific T cells," Yoonsu Choi, Carrie Yuen, Hillary Gibbons, Sourindra Maiti, Helen Huls, Sibani L Biswal, Robert Raphael, Thomas C Killian, Daniel J Stark, Dean A Lee, Partow Kebriaei, Richard E Champlin, and Laurence JN Cooper, Biology of Blood and Marrow Transplantation 15, 22 (2009).


  • Theses
  • "Measuring Dynamic Membrane Mechanical Properties Using a Combined Microfabricated Magnetic Force Transducer-Microaspiration System" Doctoral thesis by Daniel Stark (2011).

    "The Use of a Microelectroporator to Study Poration of Jurkat Cells" Master thesis by Daniel Stark (2009).

    Undergraduate Theses

    "Zeeman Tunable Saturated Absorption Spectroscopy Cell for Locking Laser Frequency to the Strontium 1S0-1P1 Transition" Michael Viray (2014).

    "Calibration of a 3D Optical Lattice" Aslak Poulsen (2014).

    "An Extended Caviity Diode Laser in Red Wavelengths" Wenmiao "Wendy" Liu (2013).

    "Characterizing a Fabry-Perot Transfer Cavity" Charles Zha (2013).

    "A Tellurium Frequency Reference For Re-pumping During Laser-cooling of Strontium" Pakorn Wongwaitayakornkul (2013).

    "Development and Use of a Saturated Absorption Spectroscopy Cell for Tuning the Frequency of the Atom-Cooling Laser" by Michael Peron (2012).

    "Three Dimensional Tissue Culturing Based On Magnetic Cell Levitation" by James Aman (2011).

    "Calibrating our Wavemeter for Spectroscopy of the 3P2-3D2 88Sr Transition" by Paul Anzel (2009).

    "A Novel Extended-Cavity Diode Laser in Red Wavelengths" by Aaron Dunn (2008).

    "Photoassociative Spectroscopy of Strontium Along the 1S0-3P1 Transition using a Littman/Metcalf Laser" by Andrew Traverso (2007).

    To learn more, contact Professor Killian or stop by the lab in Brockman Hall B16. Visitors are always welcome!


    Brockman Hall B16 Rice University 6100 Main Street Houston, TX 77005 713-348-3126
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