Atomic Physics

### Cesium bright matter-wave solitons and soliton trains (1902.03144v2)

**Tadej Mežnaršič, Tina Arh, Jure Brence, Jaka Pišljar, Katja Gosar, Žiga Gosar, Rok Žitko, Erik Zupanič, Peter Jeglič**

*2019-02-08*

A study of bright matter-wave solitons of a cesium Bose-Einstein condensate (BEC) is presented. Production of a single soliton is demonstrated and dependence of soliton atom number on the interatomic interaction is investigated. Formation of soliton trains in the quasi one-dimensional confinement is shown. Additionally, fragmentation of a BEC has been observed outside confinement, in free space. In the end a double BEC production setup for studying soliton collisions is described.

### Pair fraction in a finite temperature Fermi gas on the BEC side of the BCS-BEC crossover (1803.10598v4)

**Thomas Paintner, Daniel K. Hoffmann, Manuel Jäger, Wolfgang Limmer, Wladimir Schoch, Benjamin Deissler, Michele Pini, Pierbiagio Pieri, Giancarlo Calvanese Strinati, Cheng Chin, Johannes Hecker Denschlag**

*2018-03-28*

We investigate pairing in a strongly interacting two-component Fermi gas with positive scattering length. In this regime, pairing occurs at temperatures above the superfluid critical temperature; unbound fermions and pairs coexist in thermal equilibrium. Measuring the total number of these fermion pairs in the gas we systematically investigate the phases in the sectors of pseudogap and preformed-pair. Our measurements quantitatively test predictions from two theoretical models. Interestingly, we find that already a model based on classical atom-molecule equilibrium describes our data quite well.

### Observation of CPT for the ground hyperfine interval in Cs (1710.10788v2)

**Sumanta Khan, Vineet Bharti, Vasant Natarajan**

*2017-10-30*

We use the technique of coherent population trapping (CPT) to access the ground hyperfine interval (clock transition) in Cs. The probe and control beams required for CPT are obtained from a single compact diode laser system. The phase coherence between the beams, whose frequency difference is the clock frequency, is obtained by frequency modulating the laser with an electro-optic modulator (EOM). The EOM is fiber coupled and hence does not require alignment, and the atoms are contained in a vapor cell. Both of these should prove advantageous for potential use as atomic clocks in satellites.

### Revisiting spin-dependent forces mediated by new bosons: Potentials in the coordinate-space representation for macroscopic- and atomic-scale experiments (1810.10364v2)

**Pavel Fadeev, Yevgeny V. Stadnik, Filip Ficek, Mikhail G. Kozlov, Victor V. Flambaum, Dmitry Budker**

*2018-10-24*

The exchange of spin-0 or spin-1 bosons between fermions or spin-polarised macroscopic objects gives rise to various spin-dependent potentials. We derive the coordinate-space non-relativistic potentials induced by the exchange of such bosons, including contact terms that can play an important role in atomic-scale phenomena, and correct for errors and omissions in the literature. We summarise the properties of the potentials and their relevance for various types of experiments. These potentials underpin the interpretation of experiments that search for new bosons, including spectroscopy, torsion-pendulum measurements, magnetometry, parity nonconservation and electric dipole moment experiments.

### Suppressed spontaneous emission for coherent momentum transfer (1903.01627v1)

**Xueping Long, Seejia S. Yu, Andrew M. Jayich, Wesley C. Campbell**

*2019-03-05*

Strong optical forces with minimal spontaneous emission are desired for molecular deceleration and atom interferometry applications. We report experimental benchmarking of such a stimulated optical force driven by ultrafast laser pulses. We apply this technique to accelerate atoms, demonstrating an average of momentum transfers per spontaneous emission event. This represents more than an order of magnitude improvement in suppression of spontaneous emission compared to radiative scattering forces. For molecular beam slowing, this technique is capable of delivering a many-fold increase in the achievable time-averaged force to significantly reduce both the slowing distance and detrimental losses to dark vibrational states.

### Implementing the three-particle quantization condition including higher partial waves (1901.07095v2)

**Tyler D. Blanton, Fernando Romero-López, Stephen R. Sharpe**

*2019-01-21*

We present an implementation of the relativistic three-particle quantization condition including both - and -wave two-particle channels. For this, we develop a systematic expansion about threshold of the three-particle divergence-free K matrix, , which is a generalization of the effective range expansion of the two-particle K matrix, . Relativistic invariance plays an important role in this expansion. We find that -wave two-particle channels enter first at quadratic order. We explain how to implement the resulting multichannel quantization condition, and present several examples of its application. We derive the leading dependence of the threshold three-particle state on the two-particle -wave scattering amplitude, and use this to test our implementation. We show how strong two-particle -wave interactions can lead to significant effects on the finite-volume three-particle spectrum, including the possibility of a generalized three-particle Efimov-like bound state. We also explore the application to the system, which is accessible to lattice QCD simulations, where we study the sensitivity of the spectrum to the components of . Finally, we investigate the circumstances under which the quantization condition has unphysical solutions.

### PicoTesla absolute field readings with a hybrid 3He/87Rb magnetometer (1903.01492v1)

**Christopher Abel, Georg Bison, W. Clark Griffith, Werner Heil, Klaus Kirch, Hans-Christian Koch, Bernhard Lauss, Alexander Mtchedlishvili, Martin Pototschnig, Philipp Schmidt-Wellenburg, Allard Schnabel, Duarte Vicente Pais, Jens Voigt**

*2019-03-04*

We demonstrate the use of a hybrid He / Rb magnetometer to measure absolute magnetic fields in the pT range. The measurements were undertaken by probing time-dependent He magnetisation using Rb zero-field magnetometers. Measurements were taken to demonstrate the use of the magnetometer in cancelling residual fields within a magnetic shield. It was shown that the absolute field could be reduced to the 10 pT level by using field readings from the magnetometer. Furthermore, the hybrid magnetometer was shown to be applicable for the reduction of gradient fields by optimising the effective He time. This procedure represents a convenient and consistent way to provide a near zero magnetic field environment which can be potentially used as a base for generating desired magnetic field configurations for use in precision measurements.

### Non-adiabatic molecular association in thermal gases driven by radio-frequency pulses (1903.01389v1)

**P. Giannakeas, L. Khaykovich, Jan-Michael Rost, Chris H. Greene**

*2019-03-04*

The molecular association process in a thermal gas of Rb is investigated where the effects of the envelope of the radio-frequency field are taken into account. For experimentally relevant parameters our analysis shows that with increasing pulse length the corresponding molecular conversion efficiency exhibits low-frequency interference fringes which are robust under thermal averaging over a wide range of temperatures. This dynamical interference phenomenon is attributed to St"uckelberg phase accumulation between the low-energy continuum states and the dressed molecular state which exhibits a shift proportional to the envelope of the radio-frequency pulse intensity.

### Interactions of benzene, naphthalene, and azulene with alkali-metal and alkaline-earth-metal atoms for ultracold studies (1903.01378v1)

**Paweł Wójcik, Tatiana Korona, Michał Tomza**

*2019-03-04*

We consider collisional studies of polyatomic aromatic hydrocarbon molecules immersed into ultracold atomic gases and investigate intermolecular interactions of exemplary benzene, naphthalene, and azulene with alkali-metal (Li, Na, K, Rb, Cs) and alkaline-earth-metal (Mg, Ca, Sr, Ba) atoms. We apply the state-of-the-art ab initio techniques to compute the potential energy surfaces (PESs). We use the coupled cluster method restricted to single, double, and noniterative triple excitations to reproduce the correlation energy and the small-core energy-consistent pseudopotentials to model the scalar relativistic effects in heavier metal atoms. We also report the leading long-range isotropic and anisotropic dispersion and induction interaction coefficients. The PESs are characterized in detail and the nature of intermolecular interactions is analyzed and benchmarked using symmetry-adapted perturbation theory. The full three-dimensional PESs are provided for selected systems within the atom-bond pairwise additive representation and can be employed in scattering calculations. Presented study of the electronic structure is the first step towards the evaluation of prospects for sympathetic cooling of polyatomic aromatic molecules with ultracold atoms. We suggest azulene, an isomer of naphthalene which possesses a significant permanent electric dipole moment and optical transitions in the visible range, as a promising candidate for electric field manipulation and buffer-gas or sympathetic cooling.

### Ultra-high-speed Terahertz Imaging Using Atomic Vapour (1903.01308v1)

**Lucy A. Downes, Andrew R. MacKellar, Daniel J. Whiting, Cyril Bourgenot, Charles S. Adams, Kevin J. Weatherill**

*2019-03-04*

Terahertz (THz) technologies, generally defined as operating in the 0.1-10THz range, bridge the gap between electronic and photonic devices. Because THz radiation passes readily through materials such as plastics, paper and cloth it can be employed in non-destructive testing, and as it is non-ionising it is considered safe for security and biomedical applications. There is significant demand for high speed THz imaging across a range of applications but, despite ongoing efforts, fast full-field imaging remains an unfulfilled goal. Here we demonstrate a THz imaging system based upon efficient THz-to-optical conversion in atomic vapour, where full-field images can be collected at ultra-high speeds using conventional optical camera technology. For a 0.55 THz field we show an effective 1 cm sensor with near diffraction-limited spatial resolution and a minimum detectable power of 190 30 fW s per 40x40m pixel capable of video capture at 3000 frames per second. This combination of speed and sensitivity represents a step change in the state of the art of THz imaging, and will likely lead to its uptake in wider industrial settings. With further improvements we expect that even higher frame rates of up to 1 MHz would be possible.