We present spectroscopy of a single Rydberg atom excited within a Bose-Einstein condensate. We not only observe the density shift as discovered by Amaldi and Segrè in 1934 [1], but a line shape which changes with the principal quantum number n. The line broadening depends precisely on the interaction potential energy curves of the Rydberg electron with the neutral atom perturbers. In particular, we show the relevance of the triplet p-wave shape resonance in the e --Rb(5S) scattering, which significantly modifies the interaction potential. With a peak density of 5.5×10 14 cm -3 , and therefore an inter-particle spacing of 1300 a 0 within a Bose-Einstein condensate, the potential energy curves can be probed at these Rydberg ion -neutral atom separations. We present a simple microscopic model for the spectroscopic line shape by treating the atoms overlapped with the Rydberg orbit as zero-velocity, uncorrelated, point-like particles, with binding energies associated with their ion-neutral separation, and good agreement is found.A Rydberg atom excited in a dense background gas of atoms provides a testbed of Rydberg electron-neutral atom collisions. Spectroscopy has always been a sensitive technique for studying these collisions and in particular spectroscopy performed in a cold, dense atom sample eliminates most other line broadening mechanisms, thereby isolating the effects of elastic and inelastic electron-neutral atom collisions on the line shape. The realization of ultralong-range Rydberg molecules via elastic electronneutral collisions [2] relies on cold, dense atom samples. Since the first observation [3], Rydberg molecules continue to be realized with increasing experimental control in various potential energy landscapes and atomic species [3][4][5][6][7][8][9][10], where the neutral atom ground state wavefunction is typically bound in the outer one or two potential wells of the electron-atom potential energy curves (PECs). By applying an electric field [11] or by exciting nS states with nearly integer quantum defects, as in Cs [12], more deeply bound trilobite Rydberg molecules [2] are realized. With higher densities of cold atom samples, many neutral atoms overlap with the Rydberg orbit and the bound states become unresolvable [13,14]. By utilizing the high densities of a Bose-Einstein condensate (BEC), the neutral atoms within the Rydberg orbit provide a probe of elastic and inelastic electron-neutral collisions for a large range of ion-neutral separations. We show in this paper that Rydberg spectroscopy in a BEC allows us to probe, with high resolution, the scattering resonance directly for the first time in this temperature regime.In a completely different temperature regime (> 400 K) than the work presented here (< 1 µK), Rydberg spectroscopy done during the 1980s in unpolarized thermal vapors investigated the line shift and line broadening of Rydberg atoms excited in a background gas of the same species atoms at similar densities [15,16]. Subsequent theory work [17][18][19][20] modeled the line shapes b...
We report the creation of an interacting cold Rydberg gas of strontium atoms. We show that the excitation spectrum of the inner valence electron is sensitive to the interactions in the Rydberg gas, even though they are mediated by the outer Rydberg electron. By studying the evolution of this spectrum we observe density-dependent population transfer to a state of higher angular momentum l. We determine the fraction of Rydberg atoms transferred, and identify the dominant transfer mechanism to be l-changing electron-Rydberg collisions associated with the formation of a cold plasma. DOI: 10.1103/PhysRevLett.105.213004 PACS numbers: 32.80.Zb, 32.80.Ee, 32.80.Rm, 52.25.Ya The combination of laser-cooled atoms and the strong, tunable, long-range dipole-dipole interactions between Rydberg states has emerged as a powerful new way of studying strongly interacting quantum systems. In particular, the laser excitation of Rydberg states in cold, dense clouds can lead directly to the formation of highly entangled states via the dipole blockade mechanism [1][2][3][4]. The interatomic interactions also modify the atom-light interaction [5], giving rise to cooperative effects [6] that could be exploited to create photonic quantum gates [7]. Novel binding mechanisms give rise to long-range molecules [8,9], and the Rydberg gas has also been observed to spontaneously evolve into a plasma [10].Currently, these experiments use alkali metal atoms, where only the Rydberg electron is available for manipulation by external fields. Elements that have two valence electrons, such as strontium, provide additional degrees of freedom. The valence electron that remains in the core can be excited independently [11]. This raises the possibility of imaging [12] or laser cooling Rydberg atoms, or confining them in an optical dipole trap. A cold gas of ''planetary'' Rydberg atoms [13] could be created, where electronic correlations play an important role. The creation of highly entangled states of two-electron atoms via the Rydberg blockade could have important applications in precision frequency metrology [14].In this paper we report the creation of a cold Rydberg gas of strontium atoms. By exciting the inner valence electron, we probe the state of the outer Rydberg electron through the overlap of the two electronic wave functions. This overlap causes the doubly excited Rydberg atoms to autoionize. By measuring how the shape of the autoionizing resonance varies with density and time, we observe the transfer of population from the initially excited Rydberg state into other angular momentum states, in the presence of repulsive van der Waals interactions. Several population transfer mechanisms have been identified in cold Rydberg gases, including blackbody radiation [15], superradiance [16], resonant energy transfer due to dipole-dipole interactions [17], and electron-Rydberg collisions [18]. From a quantitative analysis of the autoionization signal, we determine that electron-Rydberg collisions associated with the formation of an ultracold plasma ...
Self organisation provides an elegant explanation for how complex structures emerge and persist throughout nature. Surprisingly often, these structures exhibit remarkably similar scale-invariant properties. While this is sometimes captured by simple models, the connection to real-world systems is exceptionally hard to test quantitatively. Here we identify three key signatures of selforganised criticality in the dynamics of a driven-dissipative gas of ultracold atoms and provide a first characterisation of its universal properties. We show that population decay drives the system to a stationary state that is largely independent of the initial conditions and exhibits scale invariance and a strong response to perturbations. This establishes a well-controlled platform for investigating self-organisation phenomena and non-equilibrium universality with unprecedented experimental access to the underlying microscopic details of the system. Self-organised criticality (SOC) is a fascinating concept, first put forward by Bak, Tang and Wiesenfeld in 1987 as a way to explain the large abundance of scale-invariant systems found in nature [1]. It is thought to underlie a wide range of complex dynamical phenomena, ranging from activity in electrical circuits and neural networks [2, 3], to the likelihood of avalanches and earthquakes [4] as well as how forest fires [5, 6], diseases [7] and even ideas spread [8]. However, despite the wide ranging fundamental and practical importance of 1 arXiv:1806.09931v2 [cond-mat.quant-gas]
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.