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Chiral light–matter interaction between photonic nanostructures with quantum emitters shows great potential to implement spin–photon interfaces for quantum information processing. Position-dependent spin momentum locking of the quantum emitter is important for these chiral coupled nanostructures. Here, we report the position-dependent chiral coupling between quantum dots (QDs) and cross waveguides both numerically and experimentally. Four quantum dots distributed at different positions in the cross section are selected to characterize the chiral properties of the device. Directional emission is achieved in a single waveguide and in both two waveguides simultaneously. In addition, the QD position can be determined with the chiral contrasts from four outputs. Therefore, the cross waveguide can function as a one-way unidirectional waveguide and a circularly polarized beam splitter by placing the QD at a rational position, which has potential applications in spin-to-path encoding for complex quantum optical networks at the single-photon level. [ABSTRACT FROM AUTHOR]

The valley of transition metal dichalcogenides provides an additional platform to manipulate spin due to its unique selection rule. Normally, intralayer optical transitions in the magnetic field show a Zeeman splitting with a g factor of about −4. Here, we report a remarkable valley Zeeman effect exhibited by the splitting of excitonic emission in a bilayer WS2, with a value of g factor as large as −16.5. The observed large g factor results from the interlayer recombination, as the conduction band and the valence band are modified in opposite directions by the magnetic field in different layers. The interlayer recombination is due to the defect induced inversion symmetry breaking, which is theoretically not accessible in ideal bilayer WS2 with inversion symmetry. The large g factor of interlayer emission offers potential benefits for future optical spin control and detection. [ABSTRACT FROM AUTHOR]

We report on an increase in the carrier tunneling time in a single quantum dot (QD) with a magnetic field in Faraday geometry using photocurrent spectroscopy. A nearly 60% increase in hole tunneling time is observed with an applied magnetic field equal to 9 T. For a truncated pyramid QD, the hole tunnels out faster at the lateral edge of the QD due to the reduced barrier height. The magnetic field in Faraday geometry shrinks the hole wave function at the center of the QD plane, which weakens the tunneling at the lateral edge and increases the average tunneling time. This mechanism also works for the electron, but the effect is smaller. The electron wave function is more localized at the center of the QD due to the uniform confining potential; therefore, the relatively weak shrinkage caused by the magnetic field does not reduce the tunneling rate significantly. [ABSTRACT FROM AUTHOR]