Analysis
of the antiferromagnetic phase transitions of the 2D
Kondo lattice
Tze Tzen Ong
Stanford
The Kondo lattice
continues to present an interesting and relevant challenge, with its
interactions between Kondo, RKKY, and coherent order. We present our study[1] of the antiferromagnetic quantum phase transitions of a 2D
Kondo-Heisenberg square lattice. Starting from the nonlinear sigma model as a
model of antiferromagnetism, we carry out a
renormalization group analysis of the competing Kondo-RKKY interaction to
one-loop order in an $\varepsilon
$-expansion. We find a new quantum critical point (QCP) strongly affected by
Kondo fluctuations. Near this QCP, there is a breakdown of hydrodynamic
behavior, and the spin waves are logarithmically frozen out. The
renormalization group results allow us to propose a new phase diagram near the antiferromagnetic fixed point of this 2D Kondo lattice
model. The T=0 phase diagram contains four phases separated by a tetracritical point, the new QCP. For small spin
fluctuations, we find a stable local magnetic moment antiferromagnet.
For stronger coupling, region II is a metallic quantum disordered paramagnet.
We find in region III a paramagnetic phase driven by Kondo interactions, with
possible ground states of a heavy fermion liquid or a
Kondo driven spin-liquid. The fourth phase is a spiral phase, or a
large-Fermi-surface antiferromagnetic phase. We will
describe these phases in more detail, including possible experimental
confirmation of the spiral phase. The existence of the tetracritical
point found here would be expected to affect the phase diagram at finite
temperatures as well. In addition, It is hoped that these results, and
particularly the Kondo interaction paramagnetic phase, will serve to bridge to
solutions starting from the opposite limit, of a Kondo effect leading to a
heavy fermion ground state. Work in collaboration
with T. Tzen Ong. \\[4pt] [1]
T. Ong and B. A. Jones, Phys. Rev. Lett. \textbf{103},
066405 (2009).