Sound velocity in spin-polarized quantum gases

Gérard Vermeulen, M. Elbel, Franck Laloë

K. D. Ivanova, A. E. Meyerovich

Eugene P. Bashkin

E. Orignac, Emeric Caprani, R. Citro

We investigate ultrasound attenuation and sound velocity shift in antiferromagnetic spin-1/2 XXZ chains in magnetic field. We relate the sound velocity shift to derivatives of the free energy with respect to exchange interactions, permitting its calculation with integrability techniques at any temperature. Using bosonization, we predict the sound velocity shift exhibits a quadratic temperature correction at low temperatures in the Tomonaga-Luttinger liquid phase. Close to the fully polarized phase, a universal behavior associated with z=2 quantum criticality is found. In the Tomonaga-Luttinger liquid phase, ultrasound attenuation obeys a scaling law as a function of wavelength and temperature. An enhancement of attenuation is obtained near the fully polarized phase.

Alfred Gold

We study spin-polarization effects in the one-dimensional electron gas with parabolic dispersion and a repulsive delta-function interaction potential. Using quasi-exact results for the unpolarized system and exact results for the fully polarized system we derive quasi-exact analytical results for the ground-state energy as a function of the spin polarization and the interaction strength. The spin susceptibility as a function of the interaction strength is calculated and compared with other calculations. We present results for the sound velocity of collective spin excitations and the sound velocity of collective density excitations.

Alexander E. Meyerovich