non-Fermi liquid

non-Fermi liquid
Name	non-Fermi liquid
Field	Condensed matter physics
Discovered	20th century

non-Fermi liquid

non-Fermi liquid refers to a class of electronic phases that deviate from the predictions of Landau's Fermi liquid theory. These phases arise in contexts ranging from correlated electron compounds to low-dimensional systems and quantum critical points, and they challenge conventional descriptions used in solid state physics. Studies of non-Fermi liquid behavior intersect with work by experimental groups and theoretical institutes worldwide.

Introduction

The concept emerged when researchers noticed anomalous transport and thermodynamic properties in materials studied by experimentalists at institutions such as Cavendish Laboratory, Bell Labs, Max Planck Institute for Solid State Research, Brookhaven National Laboratory, and Los Alamos National Laboratory. Prominent figures associated indirectly with the field include Lev Landau, John Bardeen, Philip W. Anderson, Giorgio Parisi, and Subir Sachdev. Early influential events include conferences at Bell Labs Conference Center, seminars at Institute for Advanced Study, and workshops at Kavli Institute for Theoretical Physics. Important prizes connected to underlying theory have included the Nobel Prize in Physics awarded to pioneers of quantum many-body theory.

Theoretical Background

Landau's Fermi liquid framework, developed by Lev Landau and built upon earlier work by Paul Dirac and Wolfgang Pauli, describes low-energy excitations as long-lived quasiparticles in systems such as the electron gas studied by Enrico Fermi and Eugene Wigner. Deviations were analyzed in models by theorists affiliated with Harvard University, Princeton University, University of Cambridge, Massachusetts Institute of Technology, and Stanford University. Quantum field theory techniques from groups associated with CERN and Perimeter Institute have been adapted to study singular self-energies, anomalous dimensions, and breakdowns of the quasiparticle picture. Mathematical tools developed in collaboration with researchers at Institute Henri Poincaré, CNRS, and American Mathematical Society are commonly used. Seminal theoretical frameworks were advanced by researchers at California Institute of Technology and Columbia University addressing infrared divergences and nonanalytic corrections.

Experimental Signatures

Experimental indicators were first systematically reported by groups at MIT Lincoln Laboratory, Argonne National Laboratory, Oak Ridge National Laboratory, National Institute of Standards and Technology, and RIKEN. Typical signatures include anomalous temperature dependence of resistivity seen in measurements from teams at University of Chicago and ETH Zurich, strange metal behavior studied by researchers at University of Tokyo, and specific heat anomalies reported by groups at University of California, Berkeley and University of Illinois Urbana-Champaign. Angle-resolved photoemission spectroscopy (ARPES) experiments at beamlines supported by SLAC National Accelerator Laboratory, Diamond Light Source, and European Synchrotron Radiation Facility reveal non-quasiparticle spectral lines, while neutron scattering probes at ISIS Neutron and Muon Source and Oak Ridge track unconventional spin dynamics. Transport anomalies have been correlated with Hall effect measurements by teams at Columbia University and magnetotransport studies led by groups at University of Cambridge.

Mechanisms and Models

Proposed mechanisms include critical fluctuations near quantum critical points analyzed by Subir Sachdev and colleagues, local criticality studied by groups at Yale University and University of California, Santa Barbara, and gauge-field mediated interactions formulated by researchers connected to Princeton University and University of California, Los Angeles. Models such as the Kondo lattice and multichannel Kondo problems were advanced by theorists associated with Brookhaven National Laboratory and Rutgers University, while Sachdev-Ye-Kitaev related approaches link to work by Alexei Kitaev, Subir Sachdev, and collaborators at Perimeter Institute and MIT. Low-dimensional scenarios draw on techniques from Ludwig Maximilian University of Munich and École Normale Supérieure, and holographic duality inspired models reference research from groups at Institute for Advanced Study and Stanford University.

Materials and Realizations

Materials exhibiting non-Fermi liquid behavior include heavy fermion compounds studied at Los Alamos National Laboratory and Oak Ridge, cuprate superconductors explored by teams at University of Cambridge and Bell Labs, iron-based superconductors characterized by groups at MPI für Festkörperforschung and University of Tokyo, and twisted bilayer graphene devices fabricated by researchers at Columbia University and University of Manchester. Organic charge transfer salts examined at University of Geneva and ETH Zurich, ruthenates probed by teams at Rice University, and actinide compounds investigated at Argonne National Laboratory also display related anomalies. Experimental platforms include cold atom simulators developed at Stanford University and MIT, and engineered heterostructures grown at IBM Research and Max Planck Institute for Microstructure Physics.

Open Problems and Research Directions

Outstanding problems are pursued by collaborations across National Science Foundation funded centers, European consortia including Max Planck Society and European Research Council, and international initiatives led by Japan Society for the Promotion of Science and Australian Research Council. Key challenges include establishing universal classification schemes discussed at meetings at Kavli Institute for Theoretical Physics, reconciling holographic approaches from Perimeter Institute with lattice models studied at Oak Ridge, and connecting microscopic mechanisms pursued at Columbia University with macroscopic transport anomalies observed at Brookhaven National Laboratory. Future research will likely involve interdisciplinary efforts with computational advances from Google and IBM quantum research programs, synthesis by groups at Argonne National Laboratory, and precision measurements at facilities such as SLAC National Accelerator Laboratory and Diamond Light Source.

Category:Condensed matter physics