RESUMO
Phasonic degrees of freedom are unique to quasiperiodic structures and play a central role in poorly understood properties of quasicrystals from excitation spectra to wave function statistics to electronic transport. However, phasons are challenging to access dynamically in the solid state due to their complex long-range character and the effects of disorder and strain. We report phasonic spectroscopy of a quantum gas in a one-dimensional quasicrystalline optical lattice. We observe that strong phasonic driving produces a nonperturbative high-harmonic plateau strikingly different from the effects of standard dipolar driving. Tuning the potential from crystalline to quasicrystalline, we identify spectroscopic signatures of quasiperiodicity and interactions and map the emergence of a multifractal energy spectrum, opening a path to direct imaging of the Hofstadter butterfly.
RESUMO
We report on a simple tunable laser injection-lock scheme for atomic physics experiments. Seed light from an external cavity diode laser is injected into a high-power fiber-pigtailed diode laser via a fiber optic circulator. High-power outputs (up to â¼600 mW) at the injected frequency have been obtained in a single-mode fiber with tuning over a wide wavelength range (â¼15 nm). The scheme is simpler and more cost-effective than the traditional scheme of free-space injection-locking.
RESUMO
We report the observation and characterization of position-space Bloch oscillations using cold atoms in a tilted optical lattice. While momentum-space Bloch oscillations are a common feature of optical lattice experiments, the real-space center-of-mass dynamics are typically unresolvable. In a regime of rapid tunneling and low force, we observe real-space Bloch oscillation amplitudes of hundreds of lattice sites, in both ground and excited bands. We demonstrate two unique capabilities enabled by tracking of Bloch dynamics in position space: measurement of the full position-momentum phase-space evolution during a Bloch cycle, and direct imaging of the lattice band structure. These techniques, along with the ability to exert long-distance coherent control of quantum gases without modulation, may open up new possibilities for quantum control and metrology.
RESUMO
Ultrafast electronic dynamics are typically studied using pulsed lasers. Here we demonstrate a complementary experimental approach: quantum simulation of ultrafast dynamics using trapped ultracold atoms. Counter-intuitively, this technique emulates some of the fastest processes in atomic physics with some of the slowest, leading to a temporal magnification factor of up to 12 orders of magnitude. In these experiments, time-varying forces on neutral atoms in the ground state of a tunable optical trap emulate the electric fields of a pulsed laser acting on bound charged particles. We demonstrate the correspondence with ultrafast science by a sequence of experiments: nonlinear spectroscopy of a many-body bound state, control of the excitation spectrum by potential shaping, observation of sub-cycle unbinding dynamics during strong few-cycle pulses, and direct measurement of carrier-envelope phase dependence of the response to an ultrafast-equivalent pulse. These results establish cold-atom quantum simulation as a complementary tool for studying ultrafast dynamics.
RESUMO
We report the production of ultracold 85 Rb133 Cs molecules in their rovibronic ground state X 1 Σ+ (v=0; J=0), by short-range photoassociation (PA) to the 2 1 Π1 , 2 3 Π1 , and 3 3 Σ1+ states. In the PA frequency range from 11650 to 12150â cm-1 (corresponding to energy levels 15500-16000â cm-1 above the bottom of the X potential), we have observed 40 sets of new PA lines. For selected PA states, we investigate vibrational branching, rotational branching, and saturation behavior. Among these 40 new PA lines, the 3 3 Σ1+ (v=3) state has the highest molecule production rate of 2 x 103 â molecules s-1 into the rovibronic ground state.
