Spin-orbit coupled fermions in an optical lattice clock (1608.03854v2)

Abstract: Engineered spin-orbit coupling (SOC) in cold atom systems can aid in the study of novel synthetic materials and complex condensed matter phenomena. Despite great advances, alkali atom SOC systems are hindered by heating from spontaneous emission, which limits the observation of many-body effects, motivating research into potential alternatives. Here we demonstrate that SOC can be engineered to occur naturally in a one-dimensional fermionic 87Sr optical lattice clock (OLC). In contrast to previous SOC experiments, in this work the SOC is both generated and probed using a direct ultra-narrow optical clock transition between two electronic orbital states. We use clock spectroscopy to prepare lattice band populations, internal electronic states, and quasimomenta, as well as to produce SOC dynamics. The exceptionally long lifetime of the excited clock state (160 s) eliminates decoherence and atom loss from spontaneous emission at all relevant experimental timescales, allowing subsequent momentum- and spin-resolved in situ probing of the SOC band structure and eigenstates. We utilize these capabilities to study Bloch oscillations, spin-momentum locking, and Van Hove singularities in the transition density of states. Our results lay the groundwork for the use of OLCs to probe novel SOC phases of matter.

• The paper demonstrates a novel approach to achieve spin-orbit coupling in an optical lattice clock by leveraging a direct optical transition in 87Sr.
• The methodology uses ultra-narrow linewidth transitions and clock spectroscopy to observe Bloch oscillations, spin-momentum locking, and Van Hove singularities.
• The findings pave the way for advanced quantum simulations by enabling precise studies of SOC dynamics and synthetic band structures in cold atom systems.

Spin-Orbit Coupled Fermions in an Optical Lattice Clock

The paper articulated in the paper "Spin-orbit coupled fermions in an optical lattice clock" advances the understanding of engineered spin-orbit coupling (SOC) within cold atom systems, presenting a unique approach to studying complex condensed matter phenomena. This work leverages the atomic properties of fermionic $^{87}$Sr in an optical lattice clock (OLC) to facilitate SOC, marking a departure from traditional alkali atom systems which suffer from heating-related limitations.

The paper's methodology involves the creation of SOC using a direct optical clock transition between two electronic orbital states with ultra-narrow linewidths. By utilizing the long-lived excited state of $^{87}$Sr, the researchers circumvent the decoherence and thermal issues faced in similar experiments, effectively enabling the full exploration of SOC dynamics and the characterization of SOC band structures.

Significant numerical results in the paper highlight the elimination of heating at timescales relevant to SOC investigation. The experimentally measured lifetime of the excited state extends to 160 seconds, allowing spin-resolved and momentum-resolved probing of the SOC eigenstates. Using clock spectroscopy, the authors report the direct observation of Bloch oscillations, spin-momentum locking, and Van Hove singularities, providing insights into transition densities and an effective synthetic two-dimensional system.

Key findings indicate that with open tunneling, SOC emerges intrinsically during laser interrogation in a one-dimensional fermionic optical lattice. The authors corroborate these findings with spectroscopic measurements of lattice band structures, observed as clear signatures of SOC-induced effects through splits in Rabi lines characteristic of Van Hove singularities. These observations reflect the density of states' divergence points attributed to momentum variations.

The work demonstrates the successful combination of SOC with highly controllable atomic systems in an OLC setup. The practical implications of this include the potential for probing novel SOC phases and interactions which could inform future quantum technology applications. Furthermore, the theoretical implications suggest a pathway for more extensive explorations into exotic phases in higher synthetic dimensions and the paper of topological properties in similarly engineered systems.

Looking forward, this research paves the way for more refined studies involving many-body correlations within optical lattice clocks, particularly in connection with SU(N) symmetry and the pursuit of new states of matter. The foundational methods explored could extend to lower-dimensional SOC implementations, fostering deeper investigations into quantum simulation and computation domains.

In conclusion, the paper encapsulates a significant advancement in the understanding and utility of SOC within engineered cold atom systems. The findings demonstrate both the relevance of OLCs as a platform for rich quantum mechanical investigations and their capability to address fundamental queries in condensed matter physics with enhanced precision and control.