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arXiv 2102.03530cond-mat.quant-gascond-mat.supr-con
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多带晶格中的两体问题和量子几何的作用

Two-body problem in a multiband lattice and the role of quantum geometry

M. Iskin

摘要:

考虑周期势场中的两体问题,研究了自旋- $\uparrow$费米子与自旋- $\downarrow$费米子通过短程吸引相互作用时的束缚态色散.基于变分方法,我们得到了色散的精确解的形式的一组自洽方程,并将其应用到紧束缚哈密顿现场相互作用。我们特别注意的二分晶格与两点的基础上,表现出时间反转对称性,并表明,最低能量的束缚态分散平方与动量,其有效质量张量部分控制的量子度规张量的基础布洛赫状态。特别是,我们应用我们的理论的Mielke棋盘格,并研究所发挥的特殊作用的带间过程中产生一个有限的有效质量的束缚态在一个非孤立的平带。

英文摘要:

We consider the two-body problem in a periodic potential, and study the bound-state dispersion of a spin-$\uparrow$ fermion that is interacting with a spin-$\downarrow$ fermion through a short-range attractive interaction. Based on a variational approach, we obtain the exact solution of the dispersion in the form of a set of self-consistency equations, and apply it to tight-binding Hamiltonians with onsite interactions. We pay special attention to the bipartite lattices with a two-point basis that exhibit time-reversal symmetry, and show that the lowest-energy bound states disperse quadratically with momentum, whose effective-mass tensor is partially controlled by the quantum metric tensor of the underlying Bloch states. In particular, we apply our theory to the Mielke checkerboard lattice, and study the special role played by the interband processes in producing a finite effective mass for the bound states in a non-isolated flat band.

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