Magnon spintronics is a prosperous field that promises beyond-CMOS technology based on elementary excitations of the magnetic order that act as information carriers for future computational architectures. Unidirectional propagation of spin waves is key to the realization of magnonic logic devices. However, previous efforts to enhance the Damon-Eshbach-type nonreciprocity did not realize (let alone control) purely unidirectional propagation. Here we experimentally demonstrate excitations of unidirectional exchange spin waves by a nanoscale magnetic grating consisting of Co nanowires fabricated on an ultrathin yttrium iron garnet film. We explain and model the nearly perfect unidirectional excitation by the chirality of the magneto-dipolar interactions between the Kittel mode of the nanowires and the exchange spin waves of the film. Reversal of the magnetic configurations of film and nanowire array from parallel to antiparallel changes the direction of the excited spin waves. Our results raise the prospect of a chiral magnonic logic without the need for fragile surface states.Spin waves (SWs) 1-6 can transport information in high-quality magnetic insulators such as yttrium iron garnet (YIG) 7-10 free of charge flow and with very low dissipation. Based on the interference and nonlinear interactions, the phase information of SWs 11-14 allows the design of wave-based logic circuits 15-17 for information transmission and processing with small environmental footprint. Surface SWs 18 are chiral, i.e. they propagate only in the direction of the outer product of magnetization direction and surface normal and, therefore, in opposite directions on the upper and lower film surfaces/interfaces. These "Damon-Eshbach" (DE) modes 18 are beneficial for magnonic logic devices 19 but exist only in thick magnetic films with sizable group velocities. As products of the dipolar magnetic interaction, in the case of thin films, they have small group velocities and are susceptible to surface roughness scattering. Previous efforts focused on magnetic metallic systems 20-28 with relative high dissipation. Short-wavelength spin waves 29-36 with dispersion governed by the exchange interactions, travel much faster at higher frequencies (Fig. 1d). However, pure exchange

We measure the upper state lifetime and two ratios of vibrational branching fractions f v ′ v on the B 3 Π1(v ′ ) − X 1 Σ + (v) transition of TlF. We find the B state lifetime to be 99(9) ns. We also determine that the off-diagonal vibrational decays are highly suppressed: f01/f00 < 2 × 10 −4 and f02/f00 = 1.10(6)% , in excellent agreement with their predicted values of f01/f00 < 8 × 10 −4 and f02/f00 = 1.0(2)% based on Franck-Condon factors calculated using Morse and RKR potentials. The implications of these results for the possible laser cooling of TlF and fundamental symmetries experiments are discussed.The laser cooling of molecules presents a daunting challenge with potentially rich rewards. Transverse cooling and collimation of a cold molecular beam can be accomplished by scattering a few hundred photons from each molecule, while over 10,000 photons must be scattered to bring a typical molecule in the beam to rest. It is difficult to find molecular cycling transitions that will allow so many absorption and decay cycles without significant loss to the myriad of rotational and vibrational states present in most molecular systems. In addition, successful laser cooling requires that the excited state be relatively short lived, such that it can complete many absorption/emission cycles before leaving the laser interaction region. Despite these challenges, transverse cooling has recently been achieved in strontium monofluoride [1,2].In the present paper we explore the possibility of laser cooling thallium monofluoride (TlF). High precision searches for the Schiff moment and the proton electric dipole moment (EDM) have been carried out in beams of TlF [3,4]. These experiments are tests of both parity (P) and time-reversal (T) symmetries. TlF exhibits a large enhancement in its sensitivity to such violations due to the large internal electric field of the molecule and thallium's large atomic number Z = 81 [5]. It also displays a remarkable insensitivity to systematic effects associated with external magnetic fields. The TlF experiments were largely limited by the relatively broad line widths associated with the molecules' rapid transit time through the apparatus, and the modest thermal populations of the state of interest. Using cryogenic beams and laser cooling, it may be possible to overcome these limitations and TlF might again emerge as an interesting candidate for measuring symmetry violations in the nucleus.The transition X 1 Σ + (v = 0, J P = 1 − ) − B 3 Π 1 (v ′ = 0, J ′P = 1 + ) (where J P denotes the rotational angular momentum and parity) of TlF is an interesting candidate for a cycling transition. As we argue here, it appears that this transition should be highly closed to other (unwanted) electronic, vibrational, and rotational decay paths. We begin with a discussion of electronic decay paths. The only other electronic decay transition from the B 3 Π 1 state is to the A 3 Π 0 + state (and its as-yet unobserved 3 Π 0 − partner). The branching fraction for this transition should be very small, according ...

The rotational and hyperfine spectrum of the X 1 Σ + → B 3 Π1 transition in TlF molecules was measured using laser-induced fluorescence from both a thermal and a cryogenic molecular beam. Rotational and hyperfine constants for the B state are obtained. The large magnetic hyperfine interaction of the Tl nuclear spin leads to significant mixing of the lowest B state rotational levels. Updated, more precise measurements of the B → X vibrational branching fractions are also presented. The combined rovibrational branching fractions allow for the prediction of the number of photons that can be scattered in a given TlF optical cycling scheme.

Recent experimental advances in the cooling and manipulation of bialkali dimer molecules have enabled the production of gases of ultracold molecules that are not chemically reactive. It has been presumed in the literature that in the absence of an electric field the low-energy scattering of such nonreactive molecules (NRMs) will be similar to atoms, in which a single s-wave scattering length governs the collisional physics. However, in Ref. [1], it was argued that the short-range collisional physics of NRMs is much more complex than for atoms, and that this leads to a many-body description in terms of a multi-channel Hubbard model. In this work, we show that this multi-channel Hubbard model description of NRMs in an optical lattice is robust against the approximations employed in Ref.[1] to estimate its parameters. We do so via an exact, albeit formal, derivation of a multi-channel resonance model for two NRMs from an ab initio description of the molecules in terms of their constituent atoms. We discuss the regularization of this two-body multi-channel resonance model in the presence of a harmonic trap, and how its solutions form the basis for the many-body model of Ref. [1]. We also generalize the derivation of the effective lattice model to include multiple internal states (e.g., rotational or hyperfine). We end with an outlook to future research.