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arXiv 1703.04074cond-mat.quant-gas
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振动正方形光晶格中相互作用费米子理论

Theory of interacting fermions in shaken square optical lattice

Ahmet Keles, Erhai Zhao, W. Vincent Liu

摘要:

基于时间周期调制下的轨道混合,发展了振动光晶格中弱相互作用费米子原子的理论。具体地说,我们关注的是具有近共振频率的圆振动正方形晶格中的费米子原子,即,调谐到接近于$s$ -带和$p$ -带之间的能量分离。首先,我们导出了非相互作用极限下与时间无关的四带有效哈密顿量。对角化的有效哈密顿量产生一个准能谱符合完整的数值Floquet解决方案,包括所有较高的频段。特别是,我们发现,杂交$s$带开发多个极小值,因此非平凡的费米面在不同的填充。然后,我们得到的有效相互作用的原子在杂化$s$带的解析,并表明,他们获得的费米面的动量依赖,即使裸相互作用是类接触。我们应用该理论找到了具有弱吸引相互作用的费米子的相图,并证明了其对对称性是$s+d$波。我们的理论对共振附近的振动频率范围是有效的,并且可以推广到振动晶格中相互作用费米子的其他相位。

英文摘要:

We develop a theory of weakly interacting fermionic atoms in shaken optical lattices based on the orbital mixing in the presence of time-periodic modulations. Specifically, we focus on fermionic atoms in circularly shaken square lattice with near resonance frequencies, i.e., tuned close to the energy separation between $s$-band and the $p$-bands. First, we derive a time-independent four-band effective Hamiltonian in the non-interacting limit. Diagonalization of the effective Hamiltonian yields a quasi-energy spectrum consistent with the full numerical Floquet solution that includes all higher bands. In particular, we find that the hybridized $s$-band develops multiple minima and therefore non-trivial Fermi surfaces at different fillings. We then obtain the effective interactions for atoms in the hybridized $s$-band analytically and show that they acquire momentum dependence on the Fermi surface even though the bare interaction is contact-like. We apply the theory to find the phase diagram of fermions with weak attractive interactions and demonstrate that the pairing symmetry is $s+d$-wave. Our theory is valid for a range of shaking frequencies near resonance, and it can be generalized to other phases of interacting fermions in shaken lattices.

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