Temperature Depedence of Spin and Charge Orders in the Doped Two-Dimensional Hubbard Model*

Competing and intertwined orders including inhomogeneous patterns of spin and charge are observed in many correlated electron materials, such as high-temperature superconductors. Introducing a new development of the constrained-path auxiliary-field quantum Monte Carlo (AFQMC) method, we study the interplay between thermal and quantum fluctuations in the two-dimensional Hubbard model. We obtain an accurate and systematic characterization of the evolution of the spin and charge correlations as a function of temperature T and how it connects to the ground state, at three representative doping levels δ=1/5, 1/8, and 1/10. We find increasing short-range commensurate antiferromagnetic correlations as T is lowered. As the correlation length grows sufficiently large, a modulated spin-density-wave (SDW) appears. At δ=1/5, the SDW saturates and remains short-ranged as T→0. In contrast, at δ=1/8 and 1/10 this evolves into a ground-state stripe phase. We study the relation between spin and charge orders and find that formation of charge order appears to be driven by that of the spin order. We identify a finite-temperature phase transition below which charge ordering sets in and discuss the implications of our results for the nature of this transition. Furthermore, we study effects of a nonzero next-nearest-neighbor hopping t' on the nature of spin and charge correlations.