arXiv subjects

Ian B. Spielman

Publications and source records attributed to Ian B. Spielman.

23 records · Page 2Linked to original sources

arXiv2013

Spin-orbit coupling in quantum gases

Spin-orbit coupling links a particle's velocity to its quantum mechanical spin, and is essential in numerous condensed matter phenomena, including topological insulators and Majorana fermions. In solid-state materials, spin-orbit coupling originates from the movement of electrons in a crystal's intrinsic electric field, which is uniquely prescribed. In contrast, for ultracold atomic systems, the engineered "material parameters" are tuneable: a variety of synthetic spin-orbit couplings can be engineered on demand using laser fields. Here we outline the current experimental and theoretical status of spin-orbit coupling in ultracold atomic systems, discussing unique features that enable physics impossible in any other known setting.

cond-mat.quant-gas↗

arXiv2012

Synthetic 3D Spin-Orbit Coupling

We describe a method for creating a three-dimensional analogue to Rashba spin-orbit coupling in systems of ultracold atoms. This laser induced coupling uses Raman transitions to link four internal atomic states with a tetrahedral geometry, and gives rise to a Dirac point that is robust against environmental perturbations. We present an exact result showing that such a spin-orbit coupling in a fermionic system always rise to a molecular bound state.

cond-mat.quant-gas↗

arXiv2011

Realistic Rashba and Dressehaus spin-orbit coupling for neutral atoms

We describe a new class of atom-laser coupling schemes which lead to spin-orbit coupled Hamiltonians for ultra-cold neutral atoms. By properly setting the optical phases, a pair of degenerate pseudospin states emerge as the lowest energy states in the spectrum, and are thus immune to collisionally induced decay. These schemes use $N$ cyclically coupled ground or metastable internal states. We specialize to two situations: a three level case giving fixed Rashba coupling, and a four-level case that adds a controllable Dresselhaus contribution. We describe an implementation of the four level scheme for $\Rb87$ and analyze the sensitivity of our approach to realistic experimental limitations and imperfections. Lastly, we argue that no laser coupling scheme can give pure Rashba or Dresselhaus coupling: akin to condensed matter systems, higher order terms spoil the symmetry of these couplings. However, for sufficiently intense laser fields the continuous rotational symmetry approximately holds, making the Rashba Hamiltonian applicable for cold atoms.

cond-mat.quant-gas↗

arXiv2010

A synthetic electric force acting on neutral atoms

Electromagnetism is a simple example of a gauge theory where the underlying potentials -- the vector and scalar potentials -- are defined only up to a gauge choice. The vector potential generates magnetic fields through its spatial variation and electric fields through its time-dependence. We experimentally produce a synthetic gauge field that emerges only at low energy in a rubidium Bose-Einstein condensate: the neutral atoms behave as charged particles do in the presence of a homogeneous effective vector potential. We have generated a synthetic electric field through the time dependence of an effective vector potential, a physical consequence even though the vector potential is spatially uniform.

cond-mat.quant-gas↗

arXiv2010

Synthetic magnetic fields for ultracold neutral atoms

Neutral atomic Bose condensates and degenerate Fermi gases have been used to realize important many-body phenomena in their most simple and essential forms, without many of the complexities usually associated with material systems. However, the charge neutrality of these systems presents an apparent limitation - a wide range of intriguing phenomena arise from the Lorentz force for charged particles in a magnetic field, such as the fractional quantum Hall states in two-dimensional electron systems. The limitation can be circumvented by exploiting the equivalence of the Lorentz force and the Coriolis force to create synthetic magnetic fields in rotating neutral systems. This was demonstrated by the appearance of quantized vortices in pioneering experiments on rotating quantum gases, a hallmark of superfluids or superconductors in a magnetic field. However, because of technical issues limiting the maximum rotation velocity, the metastable nature of the rotating state and the difficulty of applying stable rotating optical lattices, rotational approaches are not able to reach the large fields required for quantum Hall physics. Here, we experimentally realize an optically synthesized magnetic field for ultracold neutral atoms, made evident from the appearance of vortices in our Bose-Einstein condensate. Our approach uses a spatially-dependent optical coupling between internal states of the atoms, yielding a Berry's phase sufficient to create large synthetic magnetic fields, and is not subject to the limitations of rotating systems; with a suitable lattice configuration, it should be possible to reach the quantum Hall regime, potentially enabling studies of topological quantum computation.

cond-mat.quant-gas↗