Bulletin of the American Physical Society
54th Annual Meeting of the APS Division of Atomic, Molecular and Optical Physics
Volume 68, Number 7
Monday–Friday, June 5–9, 2023; Spokane, Washington
Session Z07: Rydberg Systems, Plasmas, and Polaritons |
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Chair: Tom Killian, Rice University Room: 206 B |
Friday, June 9, 2023 10:30AM - 10:42AM |
Z07.00001: Observation of vibrational dynamics in an ion-Rydberg molecule by a high-resolution ion microscope Moritz Berngruber, Viraatt Sai Vishwakarma Anasuri, Óscar Andrey Herrera Sancho, Yiquan Zou, Nicolas Zuber, Ruven Conrad, Florian Meinert, Robert Löw, Tilman Pfau Vibrational dynamics in conventional molecules takes usually place on a timescale of picoseconds or shorter, therefore it is hard to observe. In this talk, we report on a direct spatial observation of vibrational dynamics in an ion-Rydberg atom molecule where the vibrational dynamics happens on much slower timescales and can therefore be directly studied. |
Friday, June 9, 2023 10:42AM - 10:54AM |
Z07.00002: Blackbody Radiation Enhanced Superradiance of Ultracold Rydberg Gases Jianming Zhao, Yuechun Jiao, Zhengyang Bai, Weibin Li Superradiance describes cooperative radiation of an ensemble of dense excited atoms, in which atomic decay is synchronized collectively by vacuum photon fields. Superradiance leads to faster and stronger light emission than independent radiations. An ensemble of excited atoms can synchronize emission of light collectively in a process known as superradiance when its characteristic size is smaller than the wavelength of emitted photons. The underlying superradiance depends strongly on electromagnetic (photon) fields surrounding the atomic ensemble. The blackbody radiation (BBR) at $300$K significantly enhance decay rates of Rydberg states to neighbouring states, enabling superradiance that is not possible with bare vacuum induced spontaneous decay. Here we report observations of the superradiance of ultracold Rydberg atoms embedded in a bath of room-temperature photons. The temporal evolution of the Rydberg $|nD angle$ to $|(n+1)P angle$ superradiant decay of Cs atoms ($n$ the principal quantum number) is measured directly in free space. Theoretical simulations confirm the BBR enhanced superradiance in large Rydberg ensembles. We demonstrate that the van der Waals interactions between Rydberg atoms change the superradiant dynamics and modify the scaling of the superradiance. In the presence of static electric fields. Our study provides insights into many-body dynamics of interacting atoms coupled to thermal BBR, and might open a route to the design of blackbody thermometry at microwave frequencies via collective, dissipative photon-atom interactions. |
Friday, June 9, 2023 10:54AM - 11:06AM |
Z07.00003: Resonant energy transfer between Rydberg atoms and polar ground-state molecules at temperatures below 100 mK Junwen Zou, Stephen D Hogan Resonant energy transfer, arising as a result of dipole-dipole interactions between helium Rydberg atoms and cold ground-state ammonia molecules, has been studied at temperatures below 100 mK in an intra beam collision apparatus [1,2]. In the experiments, the atoms were prepared in triplet ns Rydberg states, with principal quantum numbers between n = 38 and 40. The process of energy transfer to np states, and l-mixed Rydberg Stark states, was tuned through resonance using electric fields up to 8 V/cm. This allowed resonance widths as low as 100 MHz to be observed. These widths are attributed to binary atom-molecule collisions at mean center-of-mass collision speeds of 20 m/s (i.e., a center-of-mass collision energy corresponding to ~100 mK). The measured resonance widths are strongly Rydberg state dependent and are broadened by van der Waals interactions that are enhanced in the presence of larger electric fields. These effects have been interpreted by comparison of the experimental data with the results of numerical calculations of the Stark shifts and the static dipole-dipole interactions in the collisions. These types of low-temperature atom-molecule interaction are of interest for cold chemistry, non-destructive detection of cold molecules, and quantum simulation [3-6]. |
Friday, June 9, 2023 11:06AM - 11:18AM |
Z07.00004: Across the threshold: From ultracold plasma to dense Rydberg gases Mario S Großmann, Julian Fiedler, Jette K Heyer, Klaus Sengstock, Markus Drescher, Philipp Wessels-Staarmann, Juliette Simonet Ultrashort laser pulses allow for local and controlled ionization of a quantum gas on femtosecond timescales. We report on the transition from ultracold plasma to dense Rydberg gases when tuning the central wavelength of a single laser pulse of 166 fs duration across the two-photon ionization threshold of ultracold 87Rb. |
Friday, June 9, 2023 11:18AM - 11:30AM |
Z07.00005: Shockwaves in Exponential Ultracold Neutral Plasmas MacKenzie Warrens, Grant M Gorman, Nina P Inman, Stephen Bradshaw, Tom C Killian Ultracold neutral plasmas (UNPs), formed by photoionizing a cloud of laser-cooled atoms, provide a powerful platform for studying various plasma phenomena due to experimental accessibility and precise control over initial conditions. They can be used to study a wide range of plasma physics, including hydrodynamic and kinetic phenomena, and magnetized and unmagnetized plasmas, as well as probe the impact of strong Coulomb coupling that is accessible because of the low temperature. The possible occurrence of shock waves in an UNP has been of interest since these systems were first created and their expansion was studied. In this talk, we will present evidence for shock waves in UNPs with an initial exponentially decaying density distribution. Signatures of shock waves exist in both the velocity and temperature profiles of the plasma. |
Friday, June 9, 2023 11:30AM - 11:42AM |
Z07.00006: Simulations and Experimental Measurement of Refilling Rates in the High-Energy Tail of the Thermal Electron Distribution of Ultra Cold Plasmas Bridget O'Mara, Ryan Baker, Jacob L Roberts Plasma electrons and ions in the high-energy tails of velocity distributions are of interest because of their importance in fusion, Tokamak, and fundamental physics research. Fusion collisions are largely between the highest-energy ions because of how their cross-section scales with energy. Runaway electrons that are of concern in fusion and Tokamak research originate from the tails of the distribution. Ultra cold plasmas (UCPs) can be studied in controlled table-top conditions, providing an excellent experimental setting for studying the behavior of the rate at which electrons populate the high-energy tail of their velocity distribution. Measured rates can be used to test theoretical descriptions that are applicable not only to electrons but other particles in the plasma. By applying electric field sequences to a UCP, we can deplete and then measure the refill rate of electrons in the high-energy tail of the velocity distribution. We can model the electric field sequences using Molecular Dynamics (MD) code to determine the optimal waveforms and timing sequences needed to avoid losing energy within the system and observe refill rates. Analysis from MD simulations and preliminary data measuring the refill rates along with descriptions of the experimental challenges will be presented. |
Friday, June 9, 2023 11:42AM - 11:54AM |
Z07.00007: Focused Ion Beam Milling with Cold Rubidium Kaih Mitchell, Rory Speirs, Christopher Billington, Andrew McCulloch, Robert E Scholten Focused ion beams (FIB) from laser-cooled atoms promise important advances in ion microscopy and nanofabrication. Low temperatures enhance beam brightness and enable higher resolution imaging and milling. More than 30 elements can be cooled, allowing for high brightness sources for many new ion species. |
Friday, June 9, 2023 11:54AM - 12:06PM |
Z07.00008: Coherent Fraction of a Uniform Two-dimensional Bose Gas in Thermal Equilibrium Hassan A Alnatah, David W Snoke, Loren N Pfeiffer, Kirk W Baldwin, Qi Yao Strong coupling of cavity photons and quantum-well excitons gives rise to new bosonic quasiparticles called exciton-polaritons. We have measured the distribution function of a homogenous polariton gas and show that it is well described by a Bose-Einstein distribution, indicating that the polariton gas is in thermal equilibrium. In addition, we measure the coherent fraction of the polariton gas by creating the interference pattern of the light emitted from the gas overlapped with its mirror image. The visibility of the interference fringes gives a direct measurement of the coherent fraction of the polariton gas as a function of the total polariton density. This allows comparison of our results with theoretical predictions of the coherent fraction of an interacting 2D Bose gas. This work connects to several fundamental questions in quantum mechanics, such as how coherence can occur spontaneously in Bose-Einstein condensates and how coherence is lost in standard quantum systems. |
Friday, June 9, 2023 12:06PM - 12:18PM |
Z07.00009: Open-system dynamics and fluctuation-dissipation relation in a photon Bose-Einstein condensate Aleksandr Sazhin, Fahri Emre Oeztuerk, Goeran Hellman, Frank Vewinger, Johann Kroha, Michiel Wouters, Martin Weitz, Julian Shmitt, Vladimir Gladilin The tunable openness of optical quantum gases, such as photon or polariton condensates in optical microcavities, enables the exploration of new system states and phases, which would not be accessible under closed system conditions. Here, we experimentally demonstrate a non-Hermitian phase transition in a photon Bose-Einstein condensate in an open dye-filled microcavity. The transition separates a phase of biexponential photon number correlations from both lasing and an intermediate, oscillatory regime, as characterised by the second-order correlation dynamics of the BEC [1]. By studying the magnitude of the condensate number fluctuations and relating them to a response function, we verify a fluctuation-dissipation relation for a BEC coupled to a molecular reservoir [2]. In more recent work, we have extended these studies to the time domain, establishing a connection between the fluctuation dynamics and the response of the condensate population to an external pulse-like perturbation of the molecular reservoir. |
Friday, June 9, 2023 12:18PM - 12:30PM |
Z07.00010: Persistent, controllable circulation of a polariton ring condensate Qi Yao, Paolo Comaron, Hassan A Alnatah, Jonathan C Beaumariage, Shouvik Mukherjee, Kenneth W West, Loren N Pfeiffer, Kirk W Baldwin, Marzena Szymańska, David W Snoke Exciton-polaritons are quasiparticles that are a superpositions of excitons and photons. In a microcavity, exciton-polaritons have an effective mass and can form a Bose-Einstein condensate (BEC). Experimentally, this condensate is generated by pumping light into a microcavity structure with quantum wells at the antinodes of the light field. The features of the polaritons are carried by the light they emit, so we can detect those by using conventional optical methods. |
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