Kibble-Zurek exponent and chiral transition of the period-4 phase of Rydberg chains

Chains of Rydberg atoms have emerged as an amazing playground to study quantum physics in 1D. Playing with inter-atomic distances and laser detuning, one can in particular explore the commensurate-incommensurate transition out of charge-density waves through the Kibble-Zurek mechanism, and the possible presence of a chiral transition with dynamical exponent $z>1$. Here we address this problem theoretically with effective blockade models where the short-distance repulsions are replaced by a constraint of no double occupancy. For the period-4 phase, we show there is an Ashkin-Teller transition point with exponent $\nu=0.78$ surrounded by a direct chiral transition with a dynamical exponent $z=1.14$ and a Kibble-Zurek exponent $\mu=0.4$. For Rydberg atoms with a van der Waals potential, we suggest that the experimental value $\mu=0.25$ is due to a chiral transition with $z\simeq 1.9$ and $\nu\simeq 0.47$ surrounding an Ashkin-Teller transition close to the 4-state Potts universality.Comment: 10 pages, 10 figures + supplemental materia

Controlling the topological sector of magnetic solitons in exfoliated Cr1/3_{1/3}NbS2_2 crystals

We investigate manifestations of topological order in monoaxial helimagnet Cr$_{1/3}$NbS$_2$ by performing transport measurements on ultra-thin crystals. Upon sweeping the magnetic field perpendicularly to the helical axis, crystals thicker than one helix pitch (48 nm) but much thinner than the magnetic domain size ($\sim$1 $\mu$m) are found to exhibit sharp and hysteretic resistance jumps. We show that these phenomena originate from transitions between topological sectors with different number of magnetic solitons. This is confirmed by measurements on crystals thinner than 48 nm --in which the topological sector cannot change-- that do not exhibit any jump or hysteresis. Our results show the ability to deterministically control the topological sector of finite-size Cr$_{1/3}$NbS$_2$ and to detect inter-sector transitions by transport measurements.Comment: 7 pages, 8 figure

Ground-State Properties of the Hydrogen Chain: Dimerization, Insulator-to-Metal Transition, and Magnetic Phases

Accurate and predictive computations of the quantum-mechanical behavior of many interacting electrons in realistic atomic environments are critical for the theoretical design of materials with desired properties, and they require solving the grand-challenge problem of the many-electron Schr\uf6dinger equation. An infinite chain of equispaced hydrogen atoms is perhaps the simplest realistic model for a bulk material, embodying several central themes of modern condensed-matter physics and chemistry while retaining a connection to the paradigmatic Hubbard model. Here, we report a combined application of cutting-edge computational methods to determine the properties of the hydrogen chain in its quantum-mechanical ground state. Varying the separation between the nuclei leads to a rich phase diagram, including a Mott phase with quasi-long-range antiferromagnetic order, electron density dimerization with power-law correlations, an insulator-to-metal transition, and an intricate set of intertwined magnetic orders