Observation of spin-space quantum transport induced by an atomic quantum point contact

Quantum transport is ubiquitous in physics. So far, quantum transport between terminals has been extensively studied in solid state systems from the fundamental point of views such as the quantized conductance to the applications to quantum devices. Recent works have demonstrated a cold-atom analog of a mesoscopic conductor by engineering a narrow conducting channel with optical potentials, which opens the door for a wealth of research of atomtronics emulating mesoscopic electronic devices and beyond. Here we realize an alternative scheme of the quantum transport experiment with ytterbium atoms in a two-orbital optical lattice system. Our system consists of a multi-component Fermi gas and a localized impurity, where the current can be created in the spin space by introducing the spin-dependent interaction with the impurity. We demonstrate a rich variety of localized-impurity-induced quantum transports, which paves the way for atomtronics exploiting spin degrees of freedom.

Calculation of Spin–orbit Couplings Using RASCI Spinless One-Particle Density Matrices: Theory and Applications

<div> <div> <div> <p>This work presents the formalism and implementation for calculations of spin–orbit couplings (SOCs) within the Breit–Pauli (BP) Hamiltonian using zero-order (non- relativistic) wave-functions described by the restricted active space configuration in- teraction (RASCI) method with general excitation operators: excitation energies, spin- flip, ionization potential, and electron attachment. The implementation is based on the application of Wigner–Eckart’s theorem within the spin space, which allows the computation of the entire SOC matrix based on the explicit calculation of just one tran- sition between the two spin-multiplets. Numeric results for a diverse set of atoms and molecules highlight the importance of balanced treatment of correlation and adequate basis sets, and illustrate overall robust performance of RASCI SOCs. The new imple- mentation is a useful addition to a methodological toolkit for studying spin-forbidden processes. </p> </div> </div> </div>

Calculation of Spin–orbit Couplings Using RASCI Spinless One-Particle Density Matrices: Theory and Applications

<div> <div> <div> <p>This work presents the formalism and implementation for calculations of spin–orbit couplings (SOCs) within the Breit–Pauli (BP) Hamiltonian using zero-order (non- relativistic) wave-functions described by the restricted active space configuration in- teraction (RASCI) method with general excitation operators: excitation energies, spin- flip, ionization potential, and electron attachment. The implementation is based on the application of Wigner–Eckart’s theorem within the spin space, which allows the computation of the entire SOC matrix based on the explicit calculation of just one tran- sition between the two spin-multiplets. Numeric results for a diverse set of atoms and molecules highlight the importance of balanced treatment of correlation and adequate basis sets, and illustrate overall robust performance of RASCI SOCs. The new imple- mentation is a useful addition to a methodological toolkit for studying spin-forbidden processes. </p> </div> </div> </div>

Classical potential for general spinning bodies

In this paper we compute the spin-dependent terms of the gravitational potential for general spinning bodies at the leading Newton’s constant G and to all orders in spin. We utilize the on-shell approach, which extracts the classical potential directly from the scattering amplitude. For spinning particles, extra care is required due to the fact that the spin space of each particle is independent. Once the appropriate matching procedures are applied, taking the classical-spin limit we obtain the potential for general spinning bodies. When the Wilson coefficients are set to unity, we successfully reproduced the potential for the Kerr black hole. Interestingly, for finite spins, we find that the finite-spin deviations from Kerr Wilson coefficients cancel with that in the matching procedure, reproducing the Kerr potential without the need for taking the classical-spin limit. Finally, we find that when cast into the chiral basis, the spin-dependence of minimal coupling exhibits factorization, allowing us to take the classical-spin limit straight forwardly.

Homogeneous spin Riemannian manifolds with the simplest Dirac operator

We show the existence of nonsymmetric homogeneous spin Riemannian manifolds whose Dirac operator is like that on a Riemannian symmetric spin space. Such manifolds are exactly the homogeneous spin Riemannian manifolds (M, g) which are traceless cyclic with respect to some quotient expression M = G/K and reductive decomposition 𝔤 = 𝔨 ⊕ 𝔪. Using transversally symmetric fibrations of noncompact type, we give a list of them.