Breakdown of Landau Theory, Fluctuations and Renormalization

Zhen Bi, Ethan Lake, T. Senthil

This work demonstrates the breakdown of the Landau paradigm - a standard symmetry breaking quantum phase transition can also admit new critical theories expressed in terms of a deconfined gauge theory coupled with massless Dirac fermions instead of the fluctuating order parameters.

Matthias Ossadnik, Carsten Honerkamp A, Thomas Maurice Rice +1 more

We use the functional renormalization group to analyze the temperature dependence of the quasiparticle scattering rates in the two-dimensional Hubbard model below half-filling. Using a band structure appropriate to overdoped Tl2Ba2CuO6+x we find a strongly angle-dependent term linearly dependent on temperature which derives from an increasing scattering vertex as the energy scale is lowered. This behavior agrees with recent experiments and confirms earlier conclusions on the origin of the breakdown of the Landau-Fermi liquid near the onset of superconductivity.

Daniel J. Amit, Víctor Martín-Mayor

Franz Wegner

Thomas Vojta, D. Belitz, Rajesh Narayanan +1 more

The quantum ferromagnetic transition of itinerant electrons is considered. It is shown that the Landau-Ginzburg-Wilson theory described by Hertz and others breaks down due to a singular coupling between fluctuations of the conserved order parameter. This coupling induces an effective long-range interaction between the spins of the form 1/ r 2 d − 1 . It leads to unusual scaling behavior at the quantum critical point in 1 < d ⩽ 3 dimensions, which is determined exactly.