Tuning of electron pairing by uniaxial strain in kagome lattices*

Unique topological and correlated phases arise in kagome lattices associated with Dirac fermions and flat dispersions in the energy spectrum [1]. In this work, we study the interplay of attractive electron interactions and topological states in strained kagome lattices via a Hubbard Hamiltonian. It has been shown that the system is driven into a charge density wave state beyond a critical attractive interaction U_c in a mean-field approximation [2]. We study the tunability of U_c employing uniaxial strains and doping levels and find interesting different phases as these physical parameters change. As uniaxial strain breaks the C₃ symmetry of the lattice, we see the onset of a charge density wave ground state even for weak attractive interaction. In the presence of spin-orbit interaction, the system changes from a quantum spin Hall state to a charge density wave at U_c for 1/3 and 2/3 filling, signaling topological phase transitions. We study the stability of these results beyond the mean-field with Density Matrix Renormalization Group calculations. This work illustrates how electronic correlations and single-particle topological structures compete to create fascinating correlated phases in kagome systems.

[1] M. A. Mojarro, and Sergio E. Ulloa. Strain-induced topological transitions and tilted Dirac cones in kagome lattices. 2024 2D Mater. 11 011001

[2] Xingchuan Zhu, Wanpeng Han, Shiping Feng, and Huaiming Guo. Quantum Monte Carlo study of the attractive kagome-lattice Hubbard model. Phys. Rev. Research 5, 023037