Quantum criticality in correlated metals

Many experiments have explored the vicinity of a magnetic ordering transition in a large number of heavy fermion materials. A description in terms on Gaussian paramagnon fluctuations often fails, suggesting that the underlying order parameter of the transition is not simply the spin density wave order. The breakdown of Kondo screening has often been proposed as the underlying physics, but it has not been clear how this can be used to define a sharp quantum critical point.

Paper 2 and paper 4 show how this conundrum can be resolved by introducing the concept of a fractionalized Fermi liquid (FL*). The FL* is Fermi liquid like in that it possesses sharp electron-like quasiparticle excitations on a Fermi surface. However it also possesses topological order and a separate set of deconfined neutral spinon excitations along with a gauge boson. The presence of topological order is intimately linked with a violation of Luttinger's theorem by the volume enclosed by the Fermi surface. The works below describe the nature of the quantum fluctuations in the vicinity of the transition between the FL* state and a conventional heavy Fermi liquid.

Paper 3 looks at related fluctuation corrections in the conventional spin density wave theory and in dynamical mean field theory.

Paper 1 looks at a very different proposal for an unconventional order parameter in a Fermi liquid, that involving fractionalization of `stripe' order.


PAPERS

  1. Strongly coupled quantum criticality with a Fermi surface in two dimensions: fractionalization of spin and charge collective modes, S. Sachdev and T. Morinari, Physical Review B 66, 235117 (2002); cond-mat/0207167.
  2. Fractionalized Fermi liquids, T. Senthil, S. Sachdev, and M. Vojta, Physical Review Letters 90, 216403 (2003); cond-mat/0209144.
  3. Non-Fermi liquid behavior from two-dimensional antiferromagnetic fluctuations: a renormalization-group and large-N analysis, S. Pankov, S. Florens, A. Georges, G. Kotliar, and S. Sachdev, Physical Review B 69, 054426 (2004); cond-mat/0304415.
  4. Weak magnetism and non-Fermi liquids near heavy-fermion critical points, T. Senthil, M. Vojta, and S. Sachdev, Physical Review B 69, 035111 (2004); cond-mat/0305193.
  5. Absence of U(1) spin liquids in two dimensions, I. F. Herbut, B. H. Seradjeh, S. Sachdev, and G. Murthy, Physical Review B 68, 195110 (2003); cond-mat/0306537. This paper has been superseded by paper 168 (cond-mat/0312617) and M. Hermele et al., cond-mat/0404751.
  6. Universal conductance of nanowires near the superconductor-metal quantum transition, S. Sachdev, P. Werner, and M. Troyer, Physical Review Letters 92, 237003 (2004); cond-mat/0402431.
  7. Quantum phase transitions out of the heavy Fermi liquid, T. Senthil, S. Sachdev, and M. Vojta, Proceedings of the International Conference on Strongly Correlated Electrons, July 26-30, 2004, Karlsruhe, Germany, cond-mat/0409033.
  8. Thermoelectric transport near pair breaking quantum phase transition out of d-wave superconductivity , D. Podolsky, A. Vishwanath, J. Moore, and S. Sachdev, cond-mat/0510597.
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