Emergent Weyl Nodes and Berry Curvature in Bose Polarons via $p$-Wave Feshbach Coupling

Abstract

We show that an impurity quasiparticle immersed in a Bose-Einstein condensate, known as a Bose polaron, exhibits topological properties characterized by a nonzero Berry curvature, which is induced by Weyl nodes that emerge via interspecies $p$-wave Feshbach resonance. Such nodes occur even in the absence of spin degrees of freedom and spin-orbit coupling. For charged impurities, the corresponding $p$-wave polarons are shown to be accompanied by chiral anomaly. The above predictions can be tested in a cold atomic environment by observing the Hall transport of the atomic or ionic impurity cloud.

Figures (2)

• Figure 1: Schematic picture of a Weyl polaron in a Bose-Einstein condensate near the boson-impurity $p$-wave Feshbach resonance. The $p$-wave coupling $g$ induces the coherent dressing of the impurity state and the Berry curvature $\bm{\Omega}=(\Omega_x,\,\Omega_y,\,\Omega_z)$, leading to the anomalous velocity $v_{\rm H}$ just like the anomalous Hall effect.
• Figure 2: (a) Polaron dispersion $E_{\kappa=\pm}(\bm{p})$ at $\bm{p}=(0,\,0,\,p_z)$, where the solid (dashed) curves represent the ground (excited)-state branch. Energy gap (b), $E_+(\bm{p})-E_{-}(\bm{p})$, and the Berry curvature (c), Eq. (\ref{['eq:9']}), are displayed in the plane of $p_\perp$ and $p_z$, where $E_{\rm W}=p_{\rm W}^2/2M_c$ is used for the normalization. In these figures, we employ $2M_c\zeta^2/E_{\rm W}=0.1$, $\mu_{c}=0$, and $M_c/M_b=6/52$.