arXiv subjects

I. Arakelyan

Publications and source records attributed to I. Arakelyan.

7 recordsLinked to original sources

arXiv2023

Verifying a quasi-classical spin model of perturbed quantum rewinding in a Fermi gas

We systematically test a quasi-classical spin model of a large spin-lattice in energy space, with a tunable, reversible Hamiltonian and effective long-range interactions. The system is simulated by a weakly interacting Fermi gas undergoing perturbed quantum rewinding using radio-frequency(RF) pulses. The model reported here is found to be in a quantitative agreement with measurements of the ensemble-averaged energy-resolved spin density. This work elucidates the effects of RF detunings on the system and measurements, pointing the way to new correlation measurement methods.

cond-mat.quant-gas↗

arXiv2021

Energy-Resolved Information Scrambling in Energy-Space Lattices

Weakly interacting Fermi gases simulate spin-lattices in energy-space, offering a rich platform for investigating information spreading and spin coherence in a large many-body quantum system. We show that the collective spin vector can be determined as a function of energy from the measured spin density, enabling general energy-space resolved protocols. We measure an out-of-time-order correlation function in this system and observe the energy dependence of the many-body coherence.

cond-mat.quant-gas↗

arXiv2021

Spin-Energy Correlation in Degenerate Weakly-Interacting Fermi Gases

Weakly interacting Fermi gases exhibit rich collective dynamics in spin-dependent potentials, arising from correlations between spin degrees of freedom and conserved single atom energies, offering broad prospects for simulating many-body quantum systems by engineering energy-space "lattices," with controlled energy landscapes and site to site interactions. Using quantum degenerate clouds of $^6$Li, confined in a spin-dependent harmonic potential, we measure complex, time-dependent spin-density profiles, varying on length scales much smaller than the cloud size. We show that a one-dimensional mean field model, without additional simplifying approximations, quantitatively predicts the observed fine structure. We measure the magnetic fields where the scattering lengths vanish for three different hyperfine state mixtures to provide new constraints on the collisional (Feshbach) resonance parameters.

cond-mat.quant-gas↗

arXiv2018

Atom Pairing in Optical Superlattices

We study the pairing of fermions in a one-dimensional lattice of tunable double-well potentials using radio-frequency spectroscopy. The spectra reveal the coexistence of two types of atom pairs with different symmetries. Our measurements are in excellent quantitative agreement with a theoretical model, obtained by extending the Green's function method of Orso et al., [Phys. Rev. Lett. 95, 060402 (2005)], to a bichromatic 1D lattice with finite harmonic radial confinement. The predicted spectra comprise hundreds of discrete transitions, with symmetry-dependent initial state populations and transition strengths. Our work provides an understanding of the elementary pairing states in a superlattice, paving the way for new studies of strongly interacting many-body systems.

cond-mat.quant-gas↗

arXiv2016

Fermi Gases in the Two-Dimensional to Quasi-Two-Dimensional Crossover

We tune the dimensionality of pancake-shaped strongly-interacting $^6$Li Fermi gas clouds from two-dimensional (2D) to quasi-2D, by controlling the ratio of the radial Fermi energy $E_F$ to the harmonic oscillator energy $hν_z$ in the tightly confined direction. In the 2D regime, where $E_F<<hν_z$, the measured radio frequency resonance spectra are in agreement with 2D-BCS theory. In the quasi-2D regime, where $E_F\simeq hν_z$, the measured spectra deviate significantly from 2D-BCS theory. For both regimes, the measured cloud radii disagree with 2D-BCS mean field theory, but agree approximately with predictions using a free energy derived from the Bethe-Goldstone equation.

cond-mat.quant-gas↗

arXiv2014

Spin-Imbalanced Quasi-Two-Dimensional Fermi Gases

We measure the density profiles for a Fermi gas of $^6$Li containing $N_1$ spin-up atoms and $N_2$ spin-down atoms, confined in a quasi-two-dimensional geometry. The spatial profiles are measured as a function of spin-imbalance $N_2/N_1$ and interaction strength, which is controlled by means of a collisional (Feshbach) resonance. The measured cloud radii and central densities are in disagreement with mean-field Bardeen-Cooper-Schrieffer theory for a true two-dimensional system. We find that the data for normal-fluid mixtures are reasonably well fit by a simple two-dimensional polaron model of the free energy. Not predicted by the model is a phase transition to a spin-balanced central core, which is observed above a critical value of $N_2/N_1$. Our observations provide important benchmarks for predictions of the phase structure of quasi-two-dimensional Fermi gases.

cond-mat.quant-gas↗

arXiv2012

Polarons in the radio-frequency spectrum of a quasi-two-dimensional Fermi gas

We measure radio-frequency spectra for a two-component mixture of a $^6$Li atomic Fermi gas in the quasi-two-dimensional regime. Near the Feshbach resonance, where the transverse Fermi energy is large compared to the confinement-induced dimer binding energies for the initial and final states, we find that the observed resonances do not correspond to transitions between confinement-induced dimers. The spectrum appears to be well-described by transitions between noninteracting polaron states in two dimensions.

cond-mat.quant-gas↗