Single impurity in ultracold Fermi superfluids

Jiang, Lei; Baksmaty, L. O.; Hu, Hui; Chen, Yan; Pu, Han

doi:10.1103/physreva.83.061604

Cited by 45 publications

(48 citation statements)

References 37 publications

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“…, which is directly related to the radio frequency (rf) spectroscopy signal [41]. With linear dispersion near Weyl nodes, we find N (E) ∝ E 2 when E → 0, which is a direct manifestation of Weyl fermions.…”

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confidence: 89%

Weyl Superfluidity in a Three-Dimensional Dipolar Fermi Gas

Liu

Yin

et al. 2015

Phys. Rev. Lett.

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Weyl superconductivity or superfluidity, a fascinating topological state of matter, features novel phenomena such as emergent Weyl fermionic excitations and anomalies. Here we report that an anisotropic Weyl superfluid state can arise as a low temperature stable phase in a 3D dipolar Fermi gas. A crucial ingredient of our model is a direction-dependent two-body effective attraction generated by a rotating external field. Experimental signatures are predicted for cold gases in radio-frequency spectroscopy. The finite temperature phase diagram of this system is studied and the transition temperature of the Weyl superfluidity is found to be within the experimental scope for atomic dipolar Fermi gases.Weyl superfluids or semimetals represent recent developments in generalizing topological phases from gapped to gapless systems (e.g., from topological insulators to semimetals), in condensed matter physics [1,2]. These Weyl states are characterized by the presence of two (or more) gapless Weyl points, which are topologically protected against small perturbations. The Weyl nodes lead to a variety of fascinating phenomena such as unusual surface states [3,4], Hall effects [5,6], and other transport features [7,8]. Finding electronic materials supporting Weyl states has attracted considerable interests [9]. There are many proposed potential candidate materials, such as the pyrochlore iridates [3], topological insulator multilayer structures [7,[10][11][12], as well as certain quasicrystals [13]. However, there is still no compelling experimental evidence for the observation of one. In the field of ultracold atoms, this phase was predicted to appear in spinorbit coupled Fermi gases [14,15]. This line of active research awaits for the future experimental breakthrough of synthesizing higher dimensional artificial spin-orbit coupling with controlled heating [16]. After all, the search for Weyl superconductors remains an open problem for both electronic and ultracold atomic systems.In this letter, we report the emergence of Weyl superfluidity in a 3D single-component dipolar Fermi gas with an effective attraction engineered by a rotating external field. Recently, degenerate dipolar Fermi gases witnessed rapid developments in both magnetic dipolar atoms (such as 167 Er [17,18] and 161 Dy [19,20] atoms) and polar molecules [21,22], stimulating tremendous interests in dipolar effects in many-body phases. The effects of the anisotropic dipolar interaction on the fermion many-body physics have been extensively investigated [23]. In particular, this provides the possibility of superfluid pairing between dipolar Fermi atoms in spinless or multicomponent systems [24][25][26][27] at low temperatures. For dipoles aligned parallel to the z direction, a p-wave superfluid state with the dominant p z symmetry was studied in a three-dimensional dipolar Fermi gas [28] and the competition between this superfluidity and nematic charge-density-wave (CDW) was also discussed [29]. For a dipolar Fermi gas confined in a 2D plane, superfluid states o...

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confidence: 89%

Weyl Superfluidity in a Three-Dimensional Dipolar Fermi Gas

Liu

Yin

et al. 2015

Phys. Rev. Lett.

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“…The universal bound state is clearly visible within the gap. Experimentally, the LDOS may be measured through spatially resolved radio-frequency (rf) spectroscopy [36], which provides a cold-atom analog of the widely used scanning tunneling microscope in the solid state [37]. The wave function of the universal bound state can therefore be determined from the real-space structure of the LDOS within the gap.…”

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confidence: 99%

Universal Impurity-Induced Bound State in Topological Superfluids

Jiang

et al. 2013

Phys. Rev. Lett.

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We predict a universal midgap bound state in topological superfluids, induced by either nonmagnetic or magnetic impurities in the strong scattering limit. This universal state is similar to the lowest-energy Caroli-de Gennes-Martricon bound state in a vortex core, but is bound to localized impurities. We argue that the observation of such a universal bound state can be a clear signature for identifying topological superfluids. We theoretically examine our argument for a spin-orbit coupled ultracold atomic Fermi gas trapped in a two-dimensional harmonic potential by performing extensive self-consistent calculations within the mean-field Bogoliubov-de Gennes theory. A realistic scenario for observing a universal bound state in ultracold 40 K atoms is proposed.

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“…They are localized in both real space (near ±x TF ) and momentum space (around k = 0). In principle, the density of states can be measured in experiment by using spatial-and momentumresolved radio-frequency spectroscopy [46].…”

Section: Topological Ff State and Majorana Modesmentioning

confidence: 99%

Spin-orbit-coupled topological Fulde-Ferrell states of fermions in a harmonic trap

et al. 2014

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Motivated by recent experimental breakthroughs in generating spin-orbit coupling in ultracold Fermi gases using Raman laser beams, we present a systematic study of spin-orbit-coupled Fermi gases confined in a quasione-dimensional trap in the presence of an in-plane Zeeman field (which can be realized using a finite two-photon Raman detuning). We find that a topological Fulde-Ferrell state will emerge, featuring finite-momentum Cooper pairing and zero-energy Majorana excitations localized near the edge of the trap based on the self-consistent Bogoliubov-de Gennes (BdG) equations. We find analytically the wave functions of the Majorana modes. Finally, using the time-dependent BdG, we show how the finite-momentum pairing field manifests itself in the expansion dynamics of the atomic cloud.

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Single impurity in ultracold Fermi superfluids

Cited by 45 publications

References 37 publications

Weyl Superfluidity in a Three-Dimensional Dipolar Fermi Gas

Weyl Superfluidity in a Three-Dimensional Dipolar Fermi Gas

Universal Impurity-Induced Bound State in Topological Superfluids

Spin-orbit-coupled topological Fulde-Ferrell states of fermions in a harmonic trap

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