Collective modes in asymmetric ultracold Fermi systems Export

@misc{citeulike:2638063, abstract = {We derive the low energy effective action for the collective modes in systems of fermions interacting via a short-range s-wave attraction, featuring unequal chemical potentials for the two fermionic species (asymmetric systems). As a consequence of the attractive interaction, fermions form a condensate that spontaneously breaks the U(1) symmetry associated with total number conservation. Therefore at sufficiently small temperatures and asymmetries, the system is a superfluid. We obtain criteria of stability for the system from the coefficients of the low energy effective Lagrangian of the modes describing fluctuations in the magnitude (Higgs mode) and in the phase (Goldstone mode) of the difermion condensate. We find that there is a region in parameter space where the system features one gapless Fermi surface, and is stable. Regions with two gapless Fermi surfaces are excluded. In the stable gapless region, for certain values of parameters, the Higgs mode is light. Its mass decreases with increasing mismatch between the chemical potentials of the two populations, if we keep the scattering length and the gap parameter constant. Furthermore, we find that the elasticity of the Higgs mode diverges at the boundary of the gapless region and these two features may lead to experimentally detectable effects. As an example, we argue that if the superfluid is put in rotation, the square of the radius of the outer core is proportional to the ratio of the Higgs elasticity and the Higgs mass. Therefore one should detect an increase in the radius of the vortex on increasing the asymmetry, when we pass through the relevant region in the gapless superfluid phase. Finally, by gauging the global U(1) symmetry, we relate the coefficients of the effective Lagrangian of the Goldstone mode with the screening masses of the gauge field.}, archivePrefix = {arXiv}, author = {Gubankova, Elena and Mannarelli, Massimo and Sharma, Rishi}, citeulike-article-id = {2638063}, citeulike-linkout-0 = {http://arxiv.org/abs/0804.0782}, citeulike-linkout-1 = {http://arxiv.org/pdf/0804.0782}, day = {4}, eprint = {0804.0782}, keywords = {eft, fermi\_gas, polarized}, month = {Apr}, posted-at = {2008-04-07 16:32:00}, priority = {2}, title = {Collective modes in asymmetric ultracold Fermi systems}, url = {http://arxiv.org/abs/0804.0782}, year = {2008} }

TY - ELEC ID - citeulike:2638063 L3 - citeulike-article-id:2638063 N2 - We derive the low energy effective action for the collective modes in systems of fermions interacting via a short-range s-wave attraction, featuring unequal chemical potentials for the two fermionic species (asymmetric systems). As a consequence of the attractive interaction, fermions form a condensate that spontaneously breaks the U(1) symmetry associated with total number conservation. Therefore at sufficiently small temperatures and asymmetries, the system is a superfluid. We obtain criteria of stability for the system from the coefficients of the low energy effective Lagrangian of the modes describing fluctuations in the magnitude (Higgs mode) and in the phase (Goldstone mode) of the difermion condensate. We find that there is a region in parameter space where the system features one gapless Fermi surface, and is stable. Regions with two gapless Fermi surfaces are excluded. In the stable gapless region, for certain values of parameters, the Higgs mode is light. Its mass decreases with increasing mismatch between the chemical potentials of the two populations, if we keep the scattering length and the gap parameter constant. Furthermore, we find that the elasticity of the Higgs mode diverges at the boundary of the gapless region and these two features may lead to experimentally detectable effects. As an example, we argue that if the superfluid is put in rotation, the square of the radius of the outer core is proportional to the ratio of the Higgs elasticity and the Higgs mass. Therefore one should detect an increase in the radius of the vortex on increasing the asymmetry, when we pass through the relevant region in the gapless superfluid phase. Finally, by gauging the global U(1) symmetry, we relate the coefficients of the effective Lagrangian of the Goldstone mode with the screening masses of the gauge field. TI - Collective modes in asymmetric ultracold Fermi systems KW - eft KW - fermi_gas KW - polarized AU - Gubankova, Elena AU - Mannarelli, Massimo AU - Sharma, Rishi PY - 2008/Apr/04/ UR - http://arxiv.org/abs/0804.0782 ER -