150 likes | 332 Views
Quantum Criticality. Condensed Matter Physics (Lee). Range for CMP. Complexity causes new physics. Classical Phase Transitions. Classical example: Phase diagram of H 2 O Notice: 1 st order and 2 nd order transitions. Experimental Evidence for Phase Transitions. Specific heat.
E N D
Condensed Matter Physics(Lee) Range for CMP Complexity causes new physics
Classical PhaseTransitions Classical example: Phase diagram of H2O Notice: 1st order and 2nd order transitions
Experimental Evidence forPhase Transitions Specific heat
The ‘Standard Model’Fermi Liquid Theory and Metals Non-classical ‘sharing’ of e- in ‘cond. band’ Band theory:
… more on metals DOS – density of states cV ~ T, r ~ T2 Metal-insulator transitions; Mott insulators Fermi Liquid Theory (Landau): quasi-particles (excitations) in ‘sea’ of fermions
What is a Quantum Phase Transition? Quantum fluctuations b/c of Heisenberg uncertainty relation: no v=0 at T=0 can cause disruptions Examples: magnetism in metals (FM / AFM) superconductivity (‘pairing’ of electrons) often combined with low dimensionality (constrained motion)
Quantum Criticality Hertz 1976 Steglich 2003
… more examples CV in HF, Steglich Hill 2001, r (T) at high B
… more examples - HTSC Lee, CQP AFM vs SC Laughlin etal Adv Phys The bigger picture: HF vs SC phase diagrams
… more examples: fract. QH Eff. Hall Effect: Lorentz force causes drift F= q(E+v x B) Quantum Hall Effect (1994): Quantized ~ h/e2 Fractional QHE quantized in non-integer steps
Comprehensive Literature List Monographs: In Physics and Electronics ed. JMT ThompsonDKK Lee AJ Schofield ‘Metals without Electrons: The Physics of Exotic Quantum Fluids’ Some figures taken from Kittel and from Omar Review Articles: Coleman Schofield Nature 433 2005, Quantum Criticality’ Laughlin, Longzarich, Monthoux, PinesAdv Phys 50(361) Hertz 1976 PRB 14 Research Articles: Nature 425 2003Doiron-Leyraud et al (Longzarich) Nature 424 2003 Custers (Steglich) The break up of heavy electrons at a QCP Nature 414 2001 Hill Breakdown of FL theory in a cuprate SC Nature 441 2006 Sebastian Nature 441 2006 Erwin ‘When is a metal not a metal?’