arXiv subjects

F. B. Dunning

Publications and source records attributed to F. B. Dunning.

18 recordsLinked to original sources

arXiv2025

Anomalies in the rotational spectra of $^{86}$Sr ULRRM dimers

Anomalies 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.

physics.atom-ph↗

arXiv2024

Elucidating the roles of collision energy and photon momentum transfer in the formation of ultralong-range Rydberg molecules

Spectroscopic 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.

physics.atom-ph↗

arXiv2023

Wave packet dynamics and long-range tunneling within the SSH model using Rydberg-atom synthetic dimensions

Rydberg-atom synthetic dimensions in the form of a lattice of n$^3S_1$ levels, $58\leq n \leq 63$, coupled through two-photon microwave excitation are used to examine dynamics within the single-particle Su-Schrieffer-Heeger (SSH) 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.

quant-ph↗

arXiv2023

Measuring nonlocal three-body spatial correlations with Rydberg trimers in ultracold quantum gases

We measure nonlocal third-order spatial correlations in non-degenerate ultracold gases of bosonic ($^{84}$Sr) and spin-polarized fermionic ($^{87}$Sr) strontium through studies of the formation rates for ultralong-range trimer Rydberg molecules. The trimer production rate is observed to be very sensitive to the effects of quantum statistics with a strong enhancement of up to a factor of six (3!) in the case of bosonic $^{84}$Sr due to bunching, and a marked reduction for spin-polarized fermionic $^{87}$Sr due to anti-bunching. The experimental results are compared to theoretical predictions and good agreement is observed. The present approach opens the way to {\it{in situ}} studies of higher-order nonlocal spatial correlations in a wide array of ultracold atomic-gas systems.

physics.atom-ph↗

arXiv2021

Realizing Su-Schrieffer-Heeger topological edge states in Rydberg-atom synthetic dimensions

We demonstrate a platform for synthetic dimensions based on coupled Rydberg levels in ultracold atoms, and we implement the single-particle Su-Schrieffer-Heeger (SSH) Hamiltonian. Rydberg levels are interpreted as synthetic lattice sites, with tunneling introduced through resonant millimeter-wave couplings. Tunneling amplitudes are controlled through the millimeter-wave amplitudes, and on-site potentials are controlled through detunings of the millimeter waves from resonance. Using alternating weak and strong tunneling with weak tunneling to edge lattice sites, we attain a configuration with symmetry-protected topological edge states. The band structure is probed through optical excitation to the Rydberg levels from the ground state, which reveals topological edge states at zero energy. We verify that edge-state energies are robust to perturbation of tunneling-rates, which preserves chiral symmetry, but can be shifted by the introduction of on-site potentials.

physics.atom-ph↗

arXiv2020

Loss rates for high-$n$, $49\lesssim n \lesssim150$, 5sns($^{3}$S$_{1}$) Rydberg atoms excited in an $^{84}$Sr Bose-Einstein condensate

Measurements of the loss rates for strontium n$^{3}$S$_{1}$ Rydberg atoms excited in a dense BEC are presented for values of principal quantum number $n$ in the range $49\lesssim n \lesssim 150$ and local atom densities of $\sim1$ to $3\times10^{14}$cm$^{-3}$. Two main processes contribute to loss, associative ionization and state-changing. The relative importance of these two loss channels is investigated and their $n$- and density-dependences are discussed using a model in which Rydberg atom loss is presumed to involve a close collision between the Rydberg core ion and ground-state atoms. The present measurements are compared to earlier results obtained using rubidium Rydberg atoms. For both species the observed loss rates are sizable, $\sim10^{5}-10^{6}$s$^{-1}$, and limit the time scales over which measurements involving Rydberg atoms immersed in quantum degenerate gases can be conducted.

physics.atom-ph↗

arXiv2020

Heteronuclear Rydberg molecules

We report the creation of heteronuclear ultralong-range Rydberg-molecule dimers by excitation of minority $^{88}\text{Sr}$ atoms to $5sns\,^3S_1$ Rydberg states ($n=31-39$) in a dense background of $^{84}\text{Sr}$. We observe an isotope shift of the $ν=0$ vibrational state over this range of $n$ and compare our measurements with a theoretical prediction and a simple scaling argument. With the appropriate choice of principal quantum number the isotope shift is sufficiently large to produce heteronuclear dimers with almost perfect fidelity. When the spectral selectivity is limited, we obtain a lower bound on the ratio of heteronuclear to homonuclear excitation probability of 30 to 1 by measuring the scaling of the molecular excitation rate with varying relative densities of $^{88}\text{Sr}$ and $^{84}\text{Sr}$ in the ultracold mixture.

physics.atom-ph↗

arXiv2019

Creation of vibrationally-excited ultralong-range Rydberg molecules in polarized and unpolarized cold gases of ${}^{87}$Sr

Photoexcitation rates for creation of ultralong-range Rydberg molecules (ULRM) with 31$\lesssim n \lesssim41$ in both ground and excited vibrational levels in cold ($T\sim900$~nK) gases of polarized and unpolarized $^{87}$Sr are presented. The measured production rates of the $ν=0, 1$ and 2 vibrational levels reveal rather different $n$ dependences which are analyzed by evaluating the Franck-Condon factors associated with excitation of the different vibrational levels and molecular rotational states. In particular, for gases of spin-polarized fermions, only Rydberg dimers with odd rotational quantum numbers are excited due to the requirement that their wavefunctions be anti-symmetric with respect to exchange. The data also demonstrate that measurements of the formation of vibrationally-excited $ν=1$ molecules can furnish a probe of pair correlations over intermediate length scales extending from $\sim20$~nm to greater than 250~nm.

physics.atom-ph↗

arXiv2019

Probing Nonlocal Spatial Correlations in Quantum Gases with Ultra-long-range Rydberg Molecules

We present photo-excitation of ultra-long-range Rydberg molecules as a probe of spatial correlations in quantum gases. Rydberg molecules can be created with well-defined internuclear spacing, set by the radius of the outer lobe of the Rydberg electron wavefunction $R_n$. By varying the principal quantum number $n$ of the target Rydberg state, the molecular excitation rate can be used to map the pair-correlation function of the trapped gas $g^{(2)}(R_n)$. We demonstrate this with ultracold Sr gases and probe pair-separation length scales ranging from $R_n = 1400 - 3200$ $a_0$, which are on the order of the thermal de Broglie wavelength for temperatures around 1 $μ$K. We observe bunching for a single-component Bose gas of $^{84}$Sr and anti-bunching due to Pauli exclusion at short distances for a polarized Fermi gas of $^{87}$Sr, revealing the effects of quantum statistics.

physics.atom-ph↗

arXiv2018

Spectroscopy of $^{87}\text{Sr}$ triplet Rydberg states

A combined experimental and theoretical spectroscopic study of high-$n$, ${30 \lesssim n \lesssim 100}$, triplet $\text{S}$ and $\text{D}$ Rydberg states in $^{87}\text{Sr}$ is presented. $^{87}\text{Sr}$ has a large nuclear spin, ${I=9/2}$, and at high-$n$ the hyperfine interaction becomes comparable to, or even larger than, the fine structure and singlet-triplet splittings which poses a considerable challenge both for precision spectroscopy and for theory. For high-$n$ $\text{S}$ states, the hyperfine shifts are evaluated non-perturbatively taking advantage of earlier spectroscopic data for the ${I=0}$ isotope $^{88}\text{Sr}$, which results in good agreement with the present measurements. For the $\text{D}$ states, this procedure is reversed by first extracting from the present $^{87}\text{Sr}$ measurements the energies of the $^{3}\text{D}_{1,2,3}$ states to be expected for isotopes without hyperfine structure ($^{88}\text{Sr}$) which allows the determination of corrected quantum defects in the high-$n$ limit.

physics.atom-ph↗

arXiv2018

Theory of excitation of Rydberg polarons in an atomic quantum gas

We present a quantum many-body description of the excitation spectrum of Rydberg polarons in a Bose gas. The many-body Hamiltonian is solved with functional determinant theory, and we extend this technique to describe Rydberg polarons of finite mass. Mean-field and classical descriptions of the spectrum are derived as approximations of the many-body theory. The various approaches are applied to experimental observations of polarons created by excitation of Rydberg atoms in a strontium Bose-Einstein condensate.

physics.atom-ph↗

arXiv2018

Creation of Rydberg Polarons in a Bose Gas

We report spectroscopic observation of Rydberg polarons in an atomic Bose gas. Polarons are created by excitation of Rydberg atoms as impurities in a strontium Bose-Einstein condensate. They are distinguished from previously studied polarons by macroscopic occupation of bound molecular states that arise from scattering of the weakly bound Rydberg electron from ground-state atoms. The absence of a $p$-wave resonance in the low-energy electron-atom scattering in Sr introduces a universal behavior in the Rydberg spectral lineshape and in scaling of the spectral width (narrowing) with the Rydberg principal quantum number, $n$. Spectral features are described with a functional determinant approach (FDA) that solves an extended Fröhlich Hamiltonian for a mobile impurity in a Bose gas. Excited states of polyatomic Rydberg molecules (trimers, tetrameters, and pentamers) are experimentally resolved and accurately reproduced with FDA.

quant-ph↗

arXiv2017

Lifetimes of ultralong-range strontium Rydberg molecules in a dense BEC

The lifetimes and decay channels of ultralong-range Rydberg molecules created in a dense BEC are examined by monitoring the time evolution of the Rydberg population using field ionization. Studies of molecules with values of principal quantum number, $n$, in the range $n=49$ to $n=72$ that contain tens to hundreds of ground state atoms within the Rydberg electron orbit show that their presence leads to marked changes in the field ionization characteristics. The Rydberg molecules have lifetimes of $\sim1-5\,μ$s, their destruction being attributed to two main processes: formation of Sr$^+_2$ ions through associative ionization, and dissociation induced through $L$-changing collisions. The observed loss rates are consistent with a reaction model that emphasizes the interaction between the Rydberg core ion and its nearest neighbor ground-state atom. The measured lifetimes place strict limits on the time scales over which studies involving Rydberg species in cold, dense atomic gases can be undertaken and limit the coherence times for such measurements.

physics.atom-ph↗

arXiv2016

Resonant Rydberg Dressing of Alkaline-Earth Atoms via Electromagnetically Induced Transparency

We develop an approach to generate finite-range atomic interactions via optical Rydberg-state excitation and study the underlying excitation dynamics in theory and experiment. In contrast to previous work, the proposed scheme is based on resonant optical driving and the establishment of a dark state under conditions of electromagnetically induced transparency (EIT). Analyzing the driven dissipative dynamics of the atomic gas, we show that the interplay between coherent light coupling, radiative decay and strong Rydberg-Rydberg atom interactions leads to the emergence of sizeable effective interactions while providing remarkably long coherence times. The latter are studied experimentally in a cold gas of strontium atoms for which the proposed scheme is most efficient. Our measured atom loss is in agreement with the theoretical prediction based on binary effective interactions between the driven atoms.

physics.atom-ph↗

arXiv2015

Lifetimes of ultra-long-range strontium Rydberg molecules

The lifetimes of the lower-lying vibrational states of ultralong-range strontium Rydberg molecules comprising one ground-state 5s2 1S0 atom and one Rydberg atom in the 5s38s 3S1 state are reported. The molecules are created in an ultracold gas held in an optical dipole trap and their numbers determined using field ionization, the product electrons being detected by a microchannel plate. The measurements show that, in marked contrast to earlier measurements involving rubidium Rydberg molecules, the lifetimes of the low-lying molecular vibrational states are very similar to those of the parent Rydberg atoms. This results because the strong p-wave resonance in low-energy electronrubidium scattering, which plays an important role in determining the molecular lifetimes, is not present for strontium. The absence of this resonance offers advantages for experiments involving strontium Rydberg atoms as impurities in quantum gases and for testing theories of molecular formation and decay.

physics.atom-ph↗

arXiv2015

Rydberg-Blockade Effects in Autler-Townes Spectra of Ultracold Strontium

We present a combined experimental and theoretical study of the effects of Rydberg interactions on Autler-Townes spectra of ultracold gases of atomic strontium. Realizing two-photon Rydberg excitation via a long-lived triplet state allows us to probe the thus far unexplored regime where Rydberg state decay presents the dominant decoherence mechanism. The effects of Rydberg interactions are observed in shifts, asymmetries, and broadening of the measured atom-loss spectra. The experiment is analyzed within a one-body density matrix approach, accounting for interaction-induced level shifts and dephasing through nonlinear terms that approximately incorporate correlations due to the Rydberg blockade. This description yields good agreement with our experimental observations for short excitation times. For longer excitation times, the loss spectrum is altered qualitatively, suggesting additional dephasing mechanisms beyond the standard blockade mechanism based on pure van der Waals interactions.

physics.atom-ph↗

arXiv2015

Ultralong-Range Rydberg Molecules in a Divalent-Atomic System

We report the creation of ultralong-range Sr$_2$ molecules comprising one ground-state $5s^2$ $^1S_0$ atom and one atom in a $5sns$ $^3S_1$ Rydberg state for $n$ ranging from 29 to 36. Molecules are created in a trapped ultracold atomic gas using two-photon excitation near resonant with the $5s5p$ $^3P_1$ intermediate state, and their formation is detected through ground-state atom loss from the trap. The observed molecular binding energies are fit with the aid of first-order perturbation theory that utilizes a Fermi pseudopotential with effective $s$-wave and $p$-wave scattering lengths to describe the interaction between an excited Rydberg electron and a ground-state Sr atom.

physics.atom-ph↗

arXiv2012

Imaging the evolution of an ultracold strontium Rydberg gas

Clouds of ultracold strontium 5s48s 1S0 or 5s47d 1D2 Rydberg atoms are created by two photon excitation of laser cooled 5s2 1S0 atoms. The spontaneous evolution of the cloud of low orbital angular momentum (low-l) Rydberg states towards an ultracold neutral plasma is observed by imaging resonant light scattered from core ions, a technique that provides both spatial and temporal resolution. Evolution is observed to be faster for the S-states, which display isotropic attractive interactions, than for the D-states, which exhibit anisotropic, principally repulsive interactions. Immersion of the atoms in a dilute ultracold neutral plasma speeds up the evolution and allows the number of Rydberg atoms initially created to be determined.

physics.atom-ph↗