Abstract. Laser trapping and interfacing of laser-cooled atoms in an optical fiber network is an important capability for quantum information science. Following the pioneering work of Balykin et al. and Vetsch et al., we propose a robust method of trapping single Cesium atoms with a two-color state-insensitive evanescent wave around a dielectric nanofiber. Specifically, we show that vector light shifts (i.e., effective inhomogeneous Zeeman broadening of the ground states) induced by the inherent ellipticity of the forward-propagating evanescent wave can be effectively canceled by a backward-propagating evanescent wave. Furthermore, by operating the trapping lasers at the magic wavelengths, we remove the differential scalar light shift between ground and excited states, thereby allowing for resonant driving of the optical D 2 transition. This scheme provides a promising approach to trap and probe neutral atoms with long trap and coherence lifetimes with realistic experimental parameters. † These authors contributed equally to this work.

Single layers of transition metal dichalcogenides are two-dimensional direct bandgap semiconductors with degenerate, but inequivalent, 'valleys' in the electronic structure that can be selectively excited by polarized light. Coherent superpositions of light and matter, exciton-polaritons, have been observed when these materials are strongly coupled to photons, but these hybrid quasiparticles do not harness the valley-sensitive excitations of monolayer transition metal dichalcogenides. Here, we demonstrate evidence for valley polarized exciton-polaritons in monolayers of MoS2 embedded in a dielectric microcavity. Unlike traditional microcavity exciton-polaritons, these light-matter quasiparticles emit polarized light with spectral Rabi splitting. The interplay of cavity-modified exciton dynamics and intervalley relaxation in the high-cooperativity regime causes valley polarized exciton-polaritons to persist to room temperature, distinct from the vanishing polarization in bare monolayers. Achieving polarization-sensitive polaritonic devices operating at room temperature presents a pathway for manipulating novel valley degrees of freedom in coherent states of light and matter.

Electrically-induced electron spin polarization is imaged in n-type ZnSe epilayers using Kerr rotation spectroscopy. Despite no evidence for an electrically-induced internal magnetic field, currentinduced in-plane spin polarization is observed with characteristic spin lifetimes that decrease with doping density. The spin Hall effect is also observed, indicated by an electrically-induced out-ofplane spin polarization with opposite sign for spins accumulating on opposite edges of the sample. The spin Hall conductivity is estimated as 3 ± 1.5 Ω −1 m −1 /|e| at 20 K, which is consistent with the extrinsic mechanism. Both the current-induced spin polarization and the spin Hall effect are observed at temperatures from 10 K to 295 K. PACS numbers: 75.25.Pn, 75.25.Dc, 71.70.Ej, 78.47.+p The ability to manipulate carrier spins in semiconductors through the spin-orbit (SO) interaction is one of the primary motivations behind the field of spintronics. SO coupling provides a mechanism for the generation and manipulation of spins solely through electric fields [1,2,3], obviating the need for applied magnetic fields. Much of the recent interest in the consequences of SO coupling in semiconductors surrounds the production of a transverse spin current from an electric current, known as the spin Hall effect. Though predicted three decades ago [4], the first experimental observations of the spin Hall effect have appeared only recently [5,6,7]. Subsequent work into the spin Hall effect has addressed the importance of extrinsic or intrinsic mechanisms of the spin Hall conductivity [7,8,9,10], the nature of spin currents [11,12], and the potential ability both to produce and to detect spin Hall currents using only electric fields [13,14].Previous experiments showing electrical generation of spin polarization in semiconductors through SO coupling have been performed at cryogenic temperatures in GaAs, the archetypical III-V zincblende semiconductor. In contrast, the wide band gap and long spin coherence times of II-VI semiconductors allow many spin-related effects to persist to higher temperatures than typically observed in the GaAs system [15]. Many of the effects of SO coupling on the electrical manipulation of spin polarization have not been studied in detail in these compounds. In ZnSe, the extrinsic SO parameter λ ZnSe = 1.06 eÅ 2 , as calculated from an extended Kane model, is five times less than that in GaAs, with λ GaAs = 5.21 eÅ 2 [10, 16]. Despite weaker SO coupling, large extrinsic SO skewscattering has been observed in the anomalous Hall effect in magnetically doped ZnSe [17]. In this Letter we optically measure electrically-induced spin polarization in ZnSe epilayers that persists to room temperature. We observe in-plane current-induced spin polarization (CISP) in ZnSe with n-doping ranging over two orders of magnitude and out-of-plane electrically-induced spin accumulation at the edges of an etched channel, providing evidence for the extrinsic spin Hall effect. Unlike in previous studies of CISP and the spin Hall eff...

Modern research in optical physics has achieved quantum control of strong interactions between a single atom and one photon within the setting of cavity quantum electrodynamics (cQED) 1 . However, to move beyond current proof-of-principle experiments involving one or two conventional optical cavities to more complex scalable systems that employ N 1 microscopic resonators 2 requires the localization of individual atoms on distance scales 100nm from a resonator's surface. In this regime an atom can be strongly coupled to a single intracavity photon 3 while at the same time experiencing significant radiative interactions with the dielectric boundaries of the resonator 4 . Here, we report an initial step into this new regime of cQED by way of real-time detection and high-bandwidth feedback to select and monitor single Cesium atoms localized ∼ 100 nm from the surface of a micro-toroidal optical resonator. We employ strong radiative interactions of atom and cavity field to probe atomic motion through the evanescent field of the resonator. Direct temporal and spectral measurements reveal both the significant role of Casimir-Polder attraction 5 and the manifestly quantum nature of the atom-cavity dynamics. Our work sets the stage for trapping atoms near micro-and nano-scopic optical resonators for applications in quantum information science, including the creation of scalable quantum networks composed of many atom-cavity systems that coherently interact via coherent exchanges of single photons 2 .The proximity of dielectric boundaries fundamentally alters atomic radiative processes as compared to quantum electrodynamics in free space. For example, freespace Lamb shifts and Einstein-A coefficients (i.e., level positions and decay rates) are modified for atom-surface distances comparable to the relevant transition wavelengths, as considered in the pioneering analyses of Casimir and Polder 5 and of Purcell 6 in the late 1940s. Seminal experiments in the 1970s investigated radiative decay for organic dye molecules near a metal mirror 7 and were followed in the 1980s by landmark observations of the inhibition of spontaneous emission for a trapped electron 8 and an atom in a waveguide 9 . The ensuing years have witnessed the development of cavity quantum electrodynamics (cQED) in this perturbative regime of boundary-modified linewidths and level shifts 4,10,11 , with applications ranging from measurements of fundamental constants 12 to the development of novel semiconductor devices 13 .With increased interaction strength, a non-perturbative regime of cQED becomes possible and is characterized not by irreversible decay but rather by the cyclic, reversible exchange of excitation between atom and photon 14 . The experimental quest for strong atomphoton coupling had its initial success in 1985 in the microwave regime with the realization of the micromaser 15 , with strong coupling in the optical domain achieved some years later 16 . By now the coherent control of atomic radiative dynamics has become possible on a photon-byphoton ...