Skyrmion defects and competing singlet orders in an antiferromagnetic Kondo lattice*

The global phase diagram of antiferromagnetic heavy fermions [1] raises the issue of how to access the paramagnetic, spin singlet states from the antiferromagnetic order. We study a honeycomb Kondo lattice starting from a non-linear sigma model representation of the local moments. The skyrmion defects of the latter are known to induce singlet orders from a perturbative gradient expansion [2]. Based on an effective Dirac Hamiltonian in the skyrmion background, we search for the various singlet orders which signify the spin singlet states upon the condensation of the skyrmions in the antiferromangetically disordered regime. We find two leading singlet channels, one in the spin Peierls and the other in the Kondo singlet [3]. The relative stability of the two are studied by varying the Kondo coupling [3]. Our results provide new insight into the global phase diagram of the heavy fermion systems.

[1] Q. Si, Phys. Status Solidi 247, 476 (2010); Physica B 378, 23 (2006).
[2] P. Goswami and Q. Si, Phys. Rev. B 89, 045124 (2014).
[3] C.C.Liu, P. Goswami and Q. Si, Phys. Rev. B 96, 125101 (2017)