Thomas C. Killian
· Dean of the Wiess School of Natural Sciences Professor, Physics and AstronomyVerifiedRice University · Physics
Active 1990–2025
About
Professor Thomas C. Killian leads research in the field of ultracold atoms and plasmas at Rice University. His group focuses on studying ultracold neutral plasmas and ultracold atomic gases, utilizing laser-cooling and trapping techniques applied to neutral strontium atoms. This laser-cooling method enables the production and confinement of atoms at temperatures as low as one millionth of a degree above absolute zero, creating exotic conditions under which matter exhibits fundamentally different behaviors. The research conducted by Professor Killian and his team explores these unique regimes to deepen the understanding of basic physical laws and to establish foundations for innovative technological advancements. His work includes pioneering studies on Rydberg-atom synthetic dimensions and laser cooling of neutral plasmas, contributing significant insights into the physics of ultracold matter.
Research topics
- Condensed matter physics
- Atomic physics
- Quantum mechanics
- Physics
- Chemistry
Selected publications
Anomalies in the rotational spectra of $^{86}$Sr ULRRM dimers
ArXiv.org · 2025-01-24
preprintOpen accessAnomalies in the rotational structure of $^{86}$Sr $^3S_1$ dimer ultralong-range Rydberg molecules (ULRRMs) created in a cold strontium gas by two-photon excitation via the intermediate $5s5p~^3P_1$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using $^{84}$Sr $^1S_0$ and $^3S_1$, and $^{86}$Sr $^1S_0$ dimers display no similar behavior, indicating that the observed behavior is peculiar to $^{86}$Sr triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for $^{84}$Sr and $^{86}$Sr, or the interchange of spin and rotational angular momentum.
Physical review. A/Physical review, A · 2025-05-09 · 1 citations
articleAnomalies in the rotational structure of $^{86}\mathrm{Sr}$ $^{3}S_{1}$ dimer ultralong-range Rydberg molecules created in a cold strontium gas by two-photon excitation via the intermediate $5s5p$ $^{3}P_{1}$ state are reported. Measurements reveal that the distribution of product rotational states is sensitive to intermediate state detuning. Comparative studies using $^{84}\mathrm{Sr}$ $^{1}S_{0}$ and $^{3}S_{1}$, and $^{86}\mathrm{Sr}$ $^{1}S_{0}$ dimers display no similar behavior, indicating that the observed behavior is peculiar to $^{86}\mathrm{Sr}$ triplet dimers. While we have no definitive hypothesis as to the physical mechanism responsible for this behavior, possible explanations might involve the very different scattering lengths for $^{84}\mathrm{Sr}$ and $^{86}\mathrm{Sr}$, or the interchange of spin and rotational angular momentum.
arXiv (Cornell University) · 2024-04-29
preprintOpen accessSenior authorWe simulate the the Su-Schrieffer-Heeger (SSH) model using Rydberg-atom synthetic dimensions constructed, in a single atom, from a ladder of six neighboring $n\:^3S_1$ Rydberg states in which adjacent states are coupled with two-photon transitions using microwave fields. Alternating strong/weak tunneling rates, controlled by adjusting the microwave amplitudes, are varied to map out the topological phase transition as a function of the ratio of the tunneling rates. For each ratio, quench dynamics experiments, in which the system is initially prepared in one of the bulk Rydberg states and then subjected to the microwave fields, are performed to measure the population evolution of the system. From the dynamics measurements, we extract the mean chiral displacement and verify that its long-time average value converges towards the system winding number. The topological phase transition is also examined by probing the energy spectrum of the system in steady state and observing the disappearance of the zero-energy edge states. The results show that even a system with as few as six levels can demonstrate the essential characteristics of the SSH Hamiltonian.
arXiv (Cornell University) · 2024-06-12
preprintOpen accessSpectroscopic measurements of the rotational distribution of $^{84}$Sr and $^{86}$Sr 5sns $^1S_0$ ultralong-range Rydberg molecular dimers created via photoassociation in a cold gas are reported. The dimers are produced by two-photon excitation via the 5s5p $^1P_1$ intermediate state. The use of singlet states permits detailed study of the roles that the initial atom-atom interaction, photon momentum transfer during Rydberg excitation, and sample temperature play in determining the spectral lineshape and final dimer rotational distribution. The results are in good agreement with the predictions of a model that includes these effects. The present work further highlights the sensitivity of ultralong-range Rydberg molecule formation to the state of the initial cold gas.
Wave steepening and shock formation in ultracold neutral plasmas
Physics of Plasmas · 2024-11-01 · 2 citations
articleOpen accessSenior authorWe present observations of wave steepening and signatures of shock formation during expansion of ultracold neutral plasmas formed with an initial density distribution that is centrally peaked and decays exponentially with distance. The plasma acceleration and velocity decrease at large distance from the plasma center, leading to central ions overtaking ions in the outer regions and the development of a steepening front that is narrow compared to the size of the plasma. The density and velocity change dramatically across the front, and significant heating of the ions is observed in the region of steepest gradients. For a reasonable estimate of electron temperature, the relative velocity of ions on either side of the front modestly exceeds the local sound speed (Mach number M≳1). This indicates that by sculpting steep density gradients, it is possible to create the conditions for shock formation, or very close to it, opening a new avenue of research for ultracold neutral plasmas.
Physical review. A/Physical review, A · 2024-09-06 · 3 citations
articleSpectroscopic measurements of the rotational distribution of $^{84}\mathrm{Sr}$ and $^{86}\mathrm{Sr}\phantom{\rule{4pt}{0ex}}\phantom{\rule{0.16em}{0ex}}5sns{\phantom{\rule{0.16em}{0ex}}}^{1}{S}_{0}$ ultralong-range Rydberg molecular dimers created via photoassociation in a cold gas are reported. The dimers are produced by two-photon excitation via the $5s5p$ $^{1}P_{1}$ intermediate state. The use of singlet states permits detailed study of the roles that the initial atom-atom interaction, photon momentum transfer during Rydberg excitation, and sample temperature play in determining the spectral line shape and final dimer rotational distribution. The results are in good agreement with the predictions of a model that includes these effects. The present work further highlights the sensitivity of ultralong-range Rydberg molecule formation to the state of the initial cold gas.
Physical review. A/Physical review, A · 2024-03-01 · 7 citations
articleSenior authorRydberg-atom synthetic dimensions in the form of a lattice of $n^{3}S_{1}$ levels, $58\ensuremath{\le}n\ensuremath{\le}63$, coupled through two-photon microwave excitation are used to examine dynamics within the single-particle Su-Schrieffer-Heeger Hamiltonian. This paradigmatic model of topological matter describes a particle hopping on a one-dimensional lattice with staggered hopping rates. Tunneling rates between lattice sites and on-site potentials are set by the microwave amplitudes and detuning, respectively. An atom is first excited to a Rydberg state that lies within the lattice and then subject to the microwave dressing fields. After some time, the dressing fields are turned off and the evolution of the population distribution in the different final lattice sites monitored using field ionization. The measurements show the existence of long-lived symmetry-protected edge states and reveal the existence of direct long-distance tunneling between the edge states. The results are in good agreement with model calculations and further demonstrate the potential of Rydberg-atom synthetic dimensions to simulate and faithfully reproduce complex Hamiltonians.
Wave Steepening and Shock Formation in Ultracold Neutral Plasmas
arXiv (Cornell University) · 2024-09-17
preprintOpen accessSenior authorWe present observations of wave steepening and signatures of shock formation during expansion of ultracold neutral plasmas formed with an initial density distribution that is centrally peaked and decays exponentially with distance. The plasma acceleration and velocity decrease at large distance from the plasma center, leading to central ions overtaking ions in the outer regions and the development of a steepening front that is narrow compared to the size of the plasma. The density and velocity change dramatically across the front, and significant heating of the ions is observed in the region of steepest gradients. For a reasonable estimate of electron temperature, the relative velocity of ions on either side of the front modestly exceeds the local sound speed (Mach number $M \gtrsim 1$). This indicates that by sculpting steep density gradients, it is possible to create the conditions for shock formation, or very close to it, opening a new avenue of research for ultracold neutral plasmas.
Physical review. A/Physical review, A · 2024-08-15 · 4 citations
articleSenior authorWe experimentally investigate the Su-Schrieffer-Heeger (SSH) Hamiltonian using Rydberg-atom synthetic dimensions constructed, in a single atom, from a ladder of six neighboring $n\phantom{\rule{0.222222em}{0ex}}^{3}S_{1}$ Rydberg states in which adjacent states are coupled with two-photon transitions using microwave fields. Alternating strong or weak tunneling rates, controlled by adjusting the microwave amplitudes, are varied to explore the topological phase transition inherent in the SSH Hamiltonian as a function of the ratio of the tunneling rates. For each ratio, quench dynamics experiments, in which the system is initially prepared in one of the bulk Rydberg states and then subjected to the microwave fields, are performed to measure the population evolution of the system. From the dynamics measurements, we extract the mean chiral displacement and verify that its long-time average value converges towards the system winding number. The loss of nontrivial topology is also examined by probing the energy spectrum of the system in steady state and observing the disappearance of the zero-energy edge states. The results show that even a system with as few as six levels can demonstrate the essential characteristics of the SSH Hamiltonian.
Physical review. A/Physical review, A · 2023-08-28 · 2 citations
articleThe authors use microwave spectroscopy to measure the quantum defects for lower-$l$ singlet strontium Rydberg states at intermediate $n$. The results are used to develop a revised set of Rydberg-Ritz quantum defect parameters that could help make accurate predictions of the energy intervals between other high-lying states.
Recent grants
Quantum Magnetism Beyond Spin Up and Spin Down
NSF · $861k · 2016–2022
Laser-Driven and Magnetized Ultracold Neutral Plasmas
NSF · $528k · 2021–2025
Rydberg Synthetic Dimensions: A New Simulator for Quantum Matter
NSF · $589k · 2021–2025
Streaming Ultracold Neutral Plasmas
NSF · $390k · 2011–2014
Equilibration and Correlations in Strongly-Coupled Plasmas
NSF · $521k · 2007–2011
Frequent coauthors
- 65 shared
F. B. Dunning
Rice University
- 48 shared
P. G. Mickelson
- 46 shared
J. D. Whalen
- 45 shared
Thomas Langin
University of Chicago
- 41 shared
Sarah Nagel
- 39 shared
Grant M. Gorman
Sandia National Laboratories
- 36 shared
S. K. Kanungo
Rice University
- 35 shared
Jose Castro
Awards & honors
- Fellow of the American Physical Society
- David and Lucille Packard Foundation Science and Engineering…
- Alfred P. Sloan Research Fellowship
- Resume-aware match score
- Save to shortlist
- AI-drafted outreach
See your match with Thomas C. Killian
PhdFit ranks faculty by your research interests, methods, and publications — grounded in their actual work, not templates.
- Free to start
- No credit card
- 30-second signup