We compute spin diffusion in a dilute Fermi gas at arbitrary temperature, polarization, and strong interaction in the normal phase using kinetic theory. While the longitudinal spin diffusivity ${D}_{\ensuremath{\parallel}}$ depends weakly on polarization and diverges for small temperatures, the transverse spin diffusivity ${D}_{\ensuremath{\perp}}$ has a strong polarization dependence and approaches a finite value for $T\ensuremath{\rightarrow}0$ in the Fermi liquid phase. For a 3D unitary Fermi gas at infinite scattering length, the diffusivities reach a minimum near the quantum limit of diffusion $\ensuremath{\hbar}/m$ in the quantum degenerate regime and are strongly suppressed by medium scattering, and we discuss the importance of the spin-rotation effect. In two dimensions, ${D}_{\ensuremath{\perp}}$ attains a minimum at strong coupling $\ensuremath{-}1\ensuremath{\lesssim}\mathrm{ln}({k}_{F}{a}_{2D})\ensuremath{\lesssim}1$ and reaches ${D}_{\ensuremath{\perp}}\ensuremath{\sim}0.2...\phantom{\rule{0.16em}{0ex}}0.3\phantom{\rule{0.16em}{0ex}}\ensuremath{\hbar}/m$ at large polarization. These values are consistent with recent measurements of two-dimensional ultracold atomic gases in the strong coupling regime.We compute spin diffusion in a dilute Fermi gas at arbitrary temperature, polarization, and strong interaction in the normal phase using kinetic theory. While the longitudinal spin diffusivity ${D}_{\ensuremath{\parallel}}$ depends weakly on polarization and diverges for small temperatures, the transverse spin diffusivity ${D}_{\ensuremath{\perp}}$ has a strong polarization dependence and approaches a finite value for $T\ensuremath{\rightarrow}0$ in the Fermi liquid phase. For a 3D unitary Fermi gas at infinite scattering length, the diffusivities reach a minimum near the quantum limit of diffusion $\ensuremath{\hbar}/m$ in the quantum degenerate regime and are strongly suppressed by medium scattering, and we discuss the importance of the spin-rotation effect. In two dimensions, ${D}_{\ensuremath{\perp}}$ attains a minimum at strong coupling $\ensuremath{-}1\ensuremath{\lesssim}\mathrm{ln}({k}_{F}{a}_{2D})\ensuremath{\lesssim}1$ and reaches ${D}_{\ensuremath{\perp}}\ensuremath{\sim}0.2...\phantom{\rule{0.16em}{0ex}}0.3\phantom{\rule{0.16em}{0ex}}\ensuremath{\hbar}/m$ at large polarization. These values are consistent with recent measurements of two-dimensional ultracold atomic gases in the strong coupling regime.

arXiv:1307.5175Physical Review ASep 27, 201319 citations

Radio-frequency spectroscopy and the dimensional crossover in interacting spin-polarized Fermi gases

Jeff Maki, Colin J. Dale, Joseph H. Thywissen +1 more

Low-dimensional ultracold gases are created in the laboratory by confining three-dimensional (3D) gases inside highly anisotropic trapping potentials. Such trap geometries not only provide access to simulating 1D and 2D physics, but also can be used to study how the character of excitations cross over to three dimensions at higher energy. In this work we study the signature in radio-frequency (rf) spectroscopy for both the 1D-to-3D and the 2D-to-3D crossovers, in spin-polarized Fermi gases. We solve the two-body scattering $T$ matrix in the presence of strong harmonic confinement and use it to evaluate both the high-frequency rf transfer rate and the two-body bound-state energies. These general expressions are then compared both to the low-dimensional limit and to the 3D limit. We find that in order to understand the dimensional crossover for spin-polarized Fermi gases with $p$ -wave interactions, one needs to take into account an emergent $s$ -wave interaction.Low-dimensional ultracold gases are created in the laboratory by confining three-dimensional (3D) gases inside highly anisotropic trapping potentials. Such trap geometries not only provide access to simulating 1D and 2D physics, but also can be used to study how the character of excitations cross over to three dimensions at higher energy. In this work we study the signature in radio-frequency (rf) spectroscopy for both the 1D-to-3D and the 2D-to-3D crossovers, in spin-polarized Fermi gases. We solve the two-body scattering $T$ matrix in the presence of strong harmonic confinement and use it to evaluate both the high-frequency rf transfer rate and the two-body bound-state energies. These general expressions are then compared both to the low-dimensional limit and to the 3D limit. We find that in order to understand the dimensional crossover for spin-polarized Fermi gases with $p$-wave interactions, one needs to take into account an emergent $s$-wave interaction.

arXiv:2407.21106Physical Review ANov 15, 20242 citations

T

matrix in the presence of strong harmonic confinement and use it to evaluate both the high-frequency rf transfer rate and the two-body bound-state energies. These general expressions are then compared both to the low-dimensional limit and to the 3D limit. We find that in order to understand the dimensional crossover for spin-polarized Fermi gases with

p

-wave interactions, one needs to take into account an emergent

s

-wave interaction.