We construct a new U(1) slave-spin representation for the single-band Hubbard model in the large-U limit. The mean-field theory in this representation is more amenable to describe both the spin-charge-separation physics of the Mott insulator at half-filling and the strange metal behavior at finite doping. By employing a dynamical Green’s function theory for slave spins, we calculate the single-particle spectral function of electrons. The result is comparable to that in dynamical mean field theories. We then formulate a dynamical t/U expansion for the doped Hubbard model that reproduces the mean-field results at the lowest order of expansion. To the next order of expansion, it naturally yields an effective low-energy theory of a t–J model for spinons self-consistently coupled to an XXZ model for the slave spins. We show that the superexchange J is renormalized by doping, in agreement with the Gutzwiller approximation. Surprisingly, we find a new ferromagnetic channel of exchange interactions which survives in the infinite U limit, as a manifestation of the Nagaoka ferromagnetism.

中文翻译：

---

掺杂哈伯德模型的动态 t/U 展开

我们构建一个新的U(1) 大范围内单带哈伯德模型的从自旋表示U限制。这种表示中的平均场理论更适合描述半填充时莫特绝缘体的自旋电荷分离物理现象和有限掺杂时的奇怪金属行为。通过采用从自旋的动力学格林函数理论，我们计算了电子的单粒子谱函数。该结果与动态平均场理论的结果相当。然后我们制定一个动态的t/U掺杂哈伯德模型的展开，以最低展开阶再现平均场结果。对于下一阶的膨胀，它自然会产生一个有效的低能理论t–J自洽耦合到的自旋子模型XXZ从机旋转的模型。我们证明了超级交易所J通过掺杂重新归一化，与 Gutzwiller 近似一致。令人惊讶的是，我们发现了一个新的铁磁无限存续的交换互动渠道U极限，作为长冈铁磁性的表现。