Yb Atoms Research Articles

Observation of Coherent Multiorbital Polarons in a Two-Dimensional Fermi Gas.

We report on the experimental observation of multiorbital polarons in a two-dimensional Fermi gas of ^{173}Yb atoms formed by mobile impurities in the metastable ^{3}P_{0} orbital and a Fermi sea in the ground-state ^{1}S_{0} orbital. We spectroscopically probe the energies of attractive and repulsive polarons close to an orbital Feshbach resonance and characterize their coherence by measuring the quasiparticle residue. For all probed interaction parameters, the repulsive polaron is a long-lived quasiparticle with a decay rate more than 2 orders of magnitude below its energy. We formulate a many-body theory, which accurately treats the interorbital interactions in two dimensions and agrees well with the experimental results. Our work paves the way for the investigation of many-body physics in multiorbital ultracold Fermi gases.

Narrow-Line Cooling and Imaging of Ytterbium Atoms in an Optical Tweezer Array.

Engineering controllable, strongly interacting many-body quantum systems is at the frontier of quantum simulation and quantum information processing. Arrays of laser-cooled neutral atoms in optical tweezers have emerged as a promising platform because of their flexibility and the potential for strong interactions via Rydberg states. Existing neutral atom array experiments utilize alkali atoms, but alkaline-earth atoms offer many advantages in terms of coherence and control, and also open the door to new applications in precision measurement and time keeping. In this Letter, we present a technique to trap individual alkaline-earth-like ytterbium (Yb) atoms in optical tweezer arrays. The narrow ^{1}S_{0}-^{3}P_{1} intercombination line is used for both cooling and imaging in a magic-wavelength optical tweezer at 532nm. The low Doppler temperature allows for imaging near the saturation intensity, resulting in a very high atom detection fidelity. We demonstrate the imaging fidelity concretely by observing rare (<1 in 10^{4} images) spontaneous quantum jumps into and out of a metastable state. We also demonstrate stochastic loading of atoms into a two-dimensional, 144-site tweezer array. This platform will enable advances in quantum information processing, quantum simulation, and precision measurement. The demonstrated narrow-line Doppler imaging may also be applied in tweezer arrays or quantum gas microscopes using other atoms with similar transitions, such as erbium and dysprosium.

IR-SPECTROSCOPY AND AFM-MICROSCOPY OF THE SURFACE OF GAMMA-IRRADIATED GaS AND GaS:Yb LAYERED SINGLE CRYSTALS

For the first time, information on the surface relief of the layered GaS and doped GaS:Yb single crystals subjected to gamma-irradiation was obtained using atomic force microscopy (AFM) and Fourier-transform infrared spectroscopy (FTIR). It was found that GaS is characterized by a non-uniform distribution of irregularities with different heights and periodicities, and when doping crystals with Yb atoms, the distribution of irregularities becomes more orderly, the height and periodicity of irregularities decreases. In the FTIR spectra, changes in the reflection coefficients of the surface of GaS and GaS:Yb single crystals are observed as a function of the gamma-irradiation dose (Фγ = 30…200 krad), and on the basis of spectroscopic and microscopic changes, it was found that doped single crystals are the most radiation-resistant.

Telecom-Band Quantum Optics with Ytterbium Atoms and Silicon Nanophotonics

Wavelengths in the telecommunication window (~1.25-1.65 microns) are ideal for quantum communication due to low transmission loss in fiber networks. To realize quantum networks operating at these wavelengths, long-lived quantum memories that couple to telecom-band photons with high efficiency need to be developed. We propose coupling neutral ytterbium atoms, which have a strong telecom-wavelength transition, to a silicon photonic crystal cavity. Specifically, we consider the 3P0-3D1 transition in neutral 171Yb to interface its long-lived nuclear spin in the metastable 3P0 'clock' state with a telecom-band photon at 1.4 microns. We show that Yb atoms can be trapped using a short wavelength (~470 nm) tweezer at a distance of 350 nm from the silicon photonic crystal cavity. At this distance, due to the slowly decaying evanescent cavity field at a longer wavelength, we obtain a single-photon Rabi frequency of g/(2pi)~100 MHz and a cooperativity of C~47 while maintaining a high photon collection efficiency into a single mode fiber. The combination of high system efficiency, telecom-band operation, and long coherence times makes this platform well suited for quantum optics on a silicon chip and long-distance quantum communication.

Antiferromagnetic interorbital spin-exchange interaction of Yb171

We report on the investigation of the scattering properties between the ground state $^1S_0$ and the metastable state $^3P_0$ of the fermionic isotope of $^{171}$Yb. We successfully measure the $s$-wave scattering lengths in the two-orbital collision channels as $a_{eg}^+=225(13)a_0$ and $a_{eg}^-=355(6)a_0$, using the clock transition spectroscopy in a three-dimensional optical lattice. The result shows that the interorbital spin-exchange interaction is antiferromagnetic, indicating that $^{171}$Yb atom is a promising isotope for the quantum simulation of the Kondo effect with the two-orbital system.

Coherent Manipulation of Orbital Feshbach Molecules of Two-Electron Atoms

Ultracold molecules have experienced increasing attention in recent years. Compared to ultracold atoms, they possess several unique properties that make them perfect candidates for the implementation of new quantum-technological applications in several fields, from quantum simulation to quantum sensing and metrology. In particular, ultracold molecules of two-electron atoms (such as strontium or ytterbium) also inherit the peculiar properties of these atomic species, above all the possibility to access metastable electronic states via direct excitation on optical clock transitions with ultimate sensitivity and accuracy. In this paper we report on the production and coherent manipulation of molecular bound states of two fermionic $^{173}$Yb atoms in different electronic (orbital) states $^1$S$_0$ and $^3$P$_0$ in proximity of a scattering resonance involving atoms in different spin and electronic states, called orbital Feshbach resonance. We demonstrate that orbital molecules can be coherently photoassociated starting from a gas of ground-state atoms in a three-dimensional optical lattices by observing several photoassociation and photodissociation cycles. We also show the possibility to coherently control the molecular internal state by using Raman-assisted transfer to swap the nuclear spin of one of the atoms forming the molecule, thus demonstrating a powerful manipulation and detection tool of these molecular bound states. Finally, by exploiting this peculiar detection technique we provide first information on the lifetime of the molecular states in a many-body setting, paving the way towards future investigations of strongly interacting Fermi gases in a still unexplored regime.

Geometrically asymmetric optical cavity for strong atom-photon coupling

Optical cavities are widely used to enhance the interaction between atoms and light. Typical designs using a geometrically symmetric structure in the near-concentric regime face a tradeoff between mechanical stability and high single-atom cooperativity. To overcome this limitation, we design and implement a geometrically asymmetric standing-wave cavity. This structure, with mirrors of very different radii of curvature, allows strong atom-light coupling while exhibiting good stability against misalignment. We observe effective cooperativities ranging from $\eta_{\rm eff}=10$ to $\eta_{\rm eff}=0.2$ by shifting the location of the atoms in the cavity mode. By loading $^{171}$Yb atoms directly from a mirror magneto-optical trap into a one-dimensional optical lattice along the cavity mode, we produce atomic ensembles with collective cooperativities up to $N\eta=2\times 10^4$. This system opens a way to preparing spin squeezing for an optical lattice clock and to accessing a range of nonclassical collective states.

Optical bistability and nonlinear dynamics by saturation of cold Yb atoms in a cavity

We observed optical bistability as well as oscillations in the upper bistable branch when cold ytterbium atoms are dispersively coupled to a high finesse optical cavity. Comparable previous observations were explained by atomic density oscillations in case of a Bose-Einstein-Condensate or optical pumping in case of a cold cloud of cesium. Both explanations do not apply in our case of thermal atoms with only a single ground state. We propose a simple two-level model including saturation to describe our experimental results. This paper introduces the experimental setup, derives the mentioned model and compares it to our experimental data. Good quantitative agreement supports our model.

Impurity problem of alkaline-earth-like atoms near an orbital Feshbach resonance

In recent years, alkaline-earth and alkaline-earth-like atoms have attracted much research interest in the field of ultracold atom. Especially, the recently discovered orbital Feshbach resonance makes it possible to investigate a strongly interacting gas of alkaline-earth or alkaline-earth-like atoms, which has greatly enriched the scope of quantum simulation in these systems. This paper focuses on the impurity problem in a Fermi gas of &lt;sup&gt;173&lt;/sup&gt;Yb atoms near orbital Feshbach resonance. In this problem, the impurity atom in &lt;sup&gt;3&lt;/sup&gt;&lt;i&gt;P&lt;/i&gt;&lt;sub&gt;0&lt;/sub&gt; state will interact with the background Fermi sea in the ground state and the molecule or polaron state will be produced out of the Fermi sea. By using the Chevy-like ansatz, we investigate the properties of the molecule and attractive polaron states firstly and a transition between these two states will be found. Then, some properties of the repulsive polaron state will be introduced, such as the effective mass and the decay rate. Furthermore, the effect of an additional Fermi sea will be considered in this system. Finally, we will discuss the impurity problem in a two-dimensional system.

A single-stage 1112 nm fiber amplifier with large gain for laser cooling of ytterbium

We present a single-stage Yb fiber amplifier pumped at 1064 nm which amplifies a low-power (5 mW) signal from a commercial distributed feedback (DFB) fiber laser at 1112 nm to several hundred mW. Compared to conventional fiber amplifiers, which are typically pumped at shorter wavelength, the single-stage gain of the amplifier is increased to more than 20 dB and the ASE level is reduced by an order of magnitude. Frequency doubling in a PPLN waveguide produces light at 556 nm, which is used to capture Yb atoms in a magneto-optical trap on the 1S0 $$\rightarrow$$ 3P1 intercombination line.

Confinement-induced resonance of alkaline-earth-metal-like atoms in anisotropic quasi-one-dimensional traps

We study the confinement-induced resonance (CIR) of $^{173}$Yb atoms near an orbital Feshbach resonance in a quasi-one-dimensional tube with transversal anisotropy. By solving the two-body scattering problem, we obtain the location of CIR for various anisotropy ratio and magnetic field. Our results show that the anisotropy of the trapping potential can serve as an additional knob to tune the location of CIR. In particular, one can shift the location of CIR to the region attainable in current experiment. We also study the energy spectrum of the system and analyze the properties of CIR from the perspective of bound states. We find that as the orbital Feshbach resonance acquires two nearly degenerate scattering channels, which in general have different threshold energies, CIR takes place when the closed channel bound state energy becomes degenerate with one of the thresholds.

Kinetics of two-pulsed photon echo formed on the 0–1 transition: isotropic and anisotropic collisions

The photon echo formed at the intercombination (6s2) 1S0 (6s6p) 3P1 (type 0–1) transition of ytterbium atoms 174Yb by two pulses of resonance radiation was investigated as a function of the time delay between exciting pulses (the photon echo kinetics). For exciting radiation pulses of the same linear polarization in the delay region 70–250 ns, the photon echo kinetics is close to the exponential one both in pure ytterbium and in its mixtures with buffer gases Ar and Xe. The relaxation cross sections were determined for all three cases, taking into account the isotopic composition of xenon and ytterbium. For the first time, the complex nonmonotonous kinetics of the collision-induced photon echo was observed in the same mixtures for the forming pulses of linear mutually orthogonal polarization. The relative efficiency of buffer atoms Yb (other isotopes than 174Yb), Xe and Ar in the collision-induced photon echo formation was obtained.

Structural and magnetic investigations of the pseudo-ternary RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) – size dependent formation of two different structure types

Abstract Several rare earth metal containing pseudo-ternary compounds in the RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) have been synthesized from the elements by arc-melting or in tantalum capsules. Within the Rh series, the compounds with RE=La–Nd crystallize in the cubic MgCu2-type (Fd3̅m) structure. For Sm besides the cubic Laves phase also the hexagonal Laves phase (MgZn2 type, P63/mmc) is found. For the remaining compounds of both series, also the hexagonal MgZn2-type structure is observed. The structures of Ho2Ru0.96(1)Al3.04(1) (a=547.4(1), c=875.7(1) pm, wR=0.0397, 201 F 2 values, 13 variables), Sc2Rh1.01(1)Al2.99(1) (a=528.0(1), c=852.8(1) pm, wR=0.0228, 184 F 2 values, 13 variables), Ho2Rh1.00(1)Al3.00(1) (a=546.5(1), c=873.8(1) pm, wR=0.0590, 222 F 2 values, 13 variables) and Tb2Ir1.06(1)Al2.94(1) (a=550.8(1), c=870.0(1) pm, wR=0.0743, 221 F 2 values, 13 variables) have been refined from single-crystal data, indicating T/Al mixing on both crystallographic Zn sites of the aristotype. The Sc, Y, La and Lu containing compounds exhibit Pauli-paramagnetic behavior, while the other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Ferro- and antiferromagnetic ordering up to T C=50.2(1) K for Gd2RhAl3 is observed, while Sm2RuAl3 shows van Vleck paramagnetism and Yb2RuAl3, finally, exhibits only partially trivalent Yb atoms, evident from a reduced magnetic moment and increased lattice parameters.

Atomic Lines of Amplified Spontaneous Emission during Optical Pumping of Yb by KrF*-Laser Radiation

Results on quasi-resonant optical pumping of Yb vapors by KrF*-laser radiation (λp = 248 nm) are presented. The radiation was converted to the visible range to be available for study. Strong lines of amplified spontaneous emission are detected. These lines are due to transitions between the groups of even (6s5d1D2, 6s6d3D1, 2, 3) and odd Yb levels (6s6p1P10, 6s6p3P 0,1,2 0 ). Coherent radiation is detected at Yb resonance lines with λ = 398.8 and 555.6 nm, which are caused, respectively, by the 6s6p1P10 → 6s6s1S0 and 6s6p3P10 → 6s6s1S0 transitions in the Yb atom. A sequence of processes that lead to the formation of inversion at the Yb atomic transitions is qualitatively examined.

Dual-Mode Operation of an Optical Lattice Clock Using Strontium and Ytterbium Atoms.

We have developed an optical lattice clock that can operate in dual modes: a strontium (Sr) clock mode and an ytterbium (Yb) clock mode. Dual-mode operation of the Sr-Yb optical lattice clock is achieved by alternately cooling and trapping 87Sr and 171Yb atoms inside the vacuum chamber of the clock. Optical lattices for Sr and Yb atoms were arranged with horizontal and vertical configurations, respectively, resulting in a small distance of the order of between the trapped Sr and Yb atoms. The 1S0-3P0 clock transitions in the trapped atoms were interrogated in turn and the clock lasers were stabilized to the transitions. We demonstrated the frequency ratio measurement of the Sr and Yb clock transitions by using the dual-mode operation of the Sr-Yb optical lattice clock. The dual-mode operation can reduce the uncertainty of the blackbody radiation shift in the frequency ratio measurement, because both Sr and Yb atoms share the same blackbody radiation.

Magic wavelengths for the transition in ytterbium atom

The static and dynamic electric dipole polarizabilities of the and states of Yb are calculated by using the relativistic ab initio method. Focusing on the red detuning region to the transition, we find two magic wavelengths at 1035.7(2) and 612.9(2) nm for the transition and three magic wavelengths at 1517.68(6), 1036.0(3) and 858(12) nm for the transitions. Such magic wavelengths are of particular interest for attaining the state-insensitive cooling, trapping, and quantum manipulation of neutral Yb atom.

Determination of static dipole polarizabilities of Yb atom**Project supported by the National Natural Science Foundation of China (Grant Nos. 91536106 and U1332206), the Strategic Priority Research Program (Category B) of the Chinese Academy of Sciences (Grant No. 21030300), and the National Key Research and Development Program of China (Grant No. 2016YFA0302104).

We determine the static values of the scalar and tensor dipole polarizabilities of the ground, 6s6p , and 6s6p states of the Yb atom. These results can be useful in many experiments undertaken using this atom. We employed a combined configuration interaction (CI) method and a second-order many-body perturbation theory (MBPT) to evaluate energies and electric dipole (E1) matrix elements of many low-lying excited states of the above atom. These values are compared with the other available theoretical calculations and experimental values. By combining these E1 matrix elements with the experimental excitation energies, we estimate the dominant valence correlation contributions to the dipole polarizabilities of the above states. The core contribution is obtained from the finite field approach. We also compare these values with the other theoretical results as there are no precise experimental values that are available for these properties.

A frequency-stabilized light source at 399 nm using an Yb hollow-cathode lamp

We demonstrate a diode laser system operating at 399 nm that is stabilized to the 6s2 1S0–6s6p 1P1 electric dipole transition in ytterbium (Yb) atoms in a hollow-cathode lamp. The frequency stability of the laser reached 1.1 × 10−11 at an averaging time of τ = 1 s. We performed an absolute frequency measurement using an optical frequency comb and determined that the absolute frequency of the laser stabilized to the 1S0–1P1 transition in 174Yb was 751 526 522.26(9) MHz. We also investigated several systematic frequency shifts while changing some of the light source parameters and measured several isotope shifts. The measured laser frequency will provide useful information regarding the practical use of the frequency-stabilized light source at 399 nm.

Hyperfine structure of 2Σ molecules containing alkaline-earth-metal atoms

Ultracold molecules with both electron spin and an electric dipole moment offer new possibilities in quantum science. We use density-functional theory to calculate hyperfine coupling constants for a selection of molecules important in this area, including RbSr, LiYb, RbYb, CaF and SrF. We find substantial hyperfine coupling constants for the fermionic isotopes of the alkaline-earth and Yb atoms. We discuss the hyperfine level patterns and Zeeman splittings expected for these molecules. The results will be important both to experiments aimed at forming ultracold open-shell molecules and to their applications.

The effect of d and f states of ytterbium on the electronic and magnetic properties of Al1−xYbxN: DFT+U study

Using density functional theory combined LSDA+U method, the structural, electronic and magnetic behaviors of ytterbium implanted in wurtzite AlN were investigated. Low formation energy shows that Yb atom favors to substitute for Al site and to confirm this stability, the adsorption energy has been calculated. It is found that Al[Formula: see text]Yb[Formula: see text]N possesses a semiconductor behavior. The magnetic moment 0.9891 [Formula: see text] per molecule principally comes from Yb ion with small contribution from the Al and N atoms. We predict that Yb ions order ferromagnetically in AlN. The hybridization between the f orbital of the Yb atom and the p orbital of the N atom is also observed. We see that AlN:Yb will be among the good candidates for spintronic applications.