We demonstrate a novel way of synthesizing spin-orbit interactions in ultracold quantum gases, based on a single-photon optical clock transition coupling two long-lived electronic states of two-electron 173 Yb atoms. By mapping the electronic states onto effective sites along a synthetic "electronic" dimension, we have engineered fermionic ladders with synthetic magnetic flux in an experimental configuration that has allowed us to achieve uniform fluxes on a lattice with minimal requirements and unprecedented tunability. We have detected the spin-orbit coupling with fiber-link-enhanced clock spectroscopy and directly measured the emergence of chiral edge currents, probing them as a function of the flux. These results open new directions for the investigation of topological states of matter with ultracold atomic gases. DOI: 10.1103/PhysRevLett.117.220401 Ultracold atoms are emerging as a very versatile platform for the investigation of topological states of matter [1], thanks to the possibility of using laser light to synthesize artificial gauge fields [2,3] and to engineer lattices with topological band structures [4][5][6][7][8]. A prime element for the emergence of nontrivial topological properties is the presence of spin-orbit coupling (SOC) [9,10], locking the spin of the particles to their motion. This interaction was first synthesized in cold atomic gases by using twophoton Raman transitions [11] coupling two hyperfine spin states with a transfer of momentum. The coupling between spin states also enables a new powerful tool for engineering topological states of matter, which relies on the "synthetic dimension" (SD) concept [12,13]. According to this approach, the internal states of an atom are treated as effective sites along a synthetic lattice dimension, and coherent coupling between them is interpreted in terms of an effective tunneling. This idea has recently been realized in Refs. [14,15], where synthetic flux ladders have been implemented by using the spin degree of freedom, and has allowed the first observation of chiral edge states in ultracold atomic systems. Its extension has inspired several proposals, opening the way, e.g., to the observation of new quantum states [16,17], to the detection of fractional charge pumping [18,19], or to the observation of the four-dimensional quantum Hall effect [20].In this Letter, we demonstrate that SOC and SDs can be efficiently implemented by exploiting different degrees of freedom, specifically, the long-lived electronic state of alkaline-earth(-like) atoms. By using the technology developed in the context of optical atomic clocks, we induce a coherent coupling between the ground state g ¼ 1 S 0 and the metastable state e ¼ 3 P 0 (lifetime ∼20 s) of ultracold 173 Yb atoms. Since the two states are separated by an optical energy, it is possible to have a sizable transfer of momentum with a single-photon transition, as pointed out An ultranarrow clock laser with wavelength λ C drives the singlephoton transition between the ground state g ¼ 1 S 0 and the long...

Chemical recognition by base complementarity in DNA and RNA is strictly related to their stereochemical order. The way in which this high stereoregular order has been achieved in a prebiotic world is not fully understood yet. More primitive systems that display complementary base recognition as a prerequisite to information and, eventually, self-replication might represent a possible route. This study investigates phosphatidylnucleosides bearing complementary bases, adenine and uridine, that can mutually recognize each other, giving mixed structures with features characteristic of complementary base pairing. Dioleoylphosphatidyl derivatives of adenosine (DOP-adenosine), uridine (DOP-uridine), and cytidine (DOP-Cytidine) have been studied at the water-air interface as a function of pH and subphase composition. When monovalent cations (Li + , Na + , and K + ) are dissolved in the subphase, the phosphatidyl derivative monolayers show expansion or compression depending on the cation nature. In particular DOP-adenosine shows a preferential interaction with Li + . The properties of mixtures of the DOP-adenosine/DOPuridine complementary bases were investigated and compared to those of the non-complementary bases (DOP-adenosine/DOP-cytidine). The results indicate a preferential interaction in a hydrophilic environment only for complementary nucleophospholipids at physiological pH, suggesting that the specific interfacial orientation of the phospholiponucleoside imposed by the interface promotes the molecular recognition between the two complementary bases in a way that resembles the Watson-Crick pairing in natural nucleic acids. Moreover, mixed monolayers of adenosine-uridine derivatives show a minimum of the free energy of mixing for DOP-uridine rich mixtures (around the DOP-adenosine/DOP-uridine ) 0.2-0.3 mole fraction) close to the stoichiometry of the trimeric adduct (uridine) 2‚adenosine that forms in highly concentrated solutions of uridine and adenosine, where adenosine displays simultaneously the Watson-Crick and the Hoogsten hydrogen bond patterns.

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 S0 and 3 P0 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.

We report on the measurement of the scattering properties of ultracold 174 Yb bosons in a threedimensional optical lattice. Site occupancy in an atomic Mott insulator is resolved with high-precision spectroscopy on an ultranarrow, metrological optical clock transition. Scattering lengths and loss rate coefficients for 174 Yb atoms in different collisional channels involving the ground state 1 S 0 and the metastable 3 P 0 states are derived. These studies set important constraints for future experimental studies of two-electron atoms for quantum-technological applications.