1. How might a Fermi surface die?
T. Senthil

2. Electrons in metals

3. Modern solid state physics

4. A common phase diagram Non Fermi Liquid T Phase A Phase B Tuning
parameter

5. Example 1: High temperature superconducting materials
Pseudo
gap
AF Mott
insulator
Non-fermi
liquid metal
Fermi liquid

6. Example 2: Magnetic ordering in certain rare earth alloys CePd2Si2, CeCu6-xAux, YbRh2Si2,……
Metal
Non –fermi liquid

7. Representative data on YbRh2Si2
Custers et al, Nature, 2003
Trovarelli et al, PRL 2000
B(T)
T-dependence of resistivity at
critical point: ρ(T) ~ T for three
decades in temperature!
Fermi liquid
Magnetic metal
Non fermi liquid

8. Origin of non-fermi liquid physics?T
Tuning
parameter
Phase A
Phase B
Non
Fermi Liquid

9. So possibly……….

10. Recent clue from experiments

11. Killing a Fermi surface

12. Geometry of Fermi surface of CeRhIn5
Example: Evolution of Fermi surface across the
magnetic phase transition in CeRhIn5
H. Shishido, R. Settai, H. Harima, & Y. Onuki, JPSJ 74, 1103 (2005)

13. A simple theoretical example

14. Evolution from metal to insulator

15. Possible experimental realization of a second order Mott transition

16. Another example: High temperature superconducting materials
Pseudo
gap
AF Mott
insulator
Non-fermi
liquid metal
Fermi liquid

18. Basic question for theory
How can an entire Fermi surface disappear continuously?

19. Even more basic: What is the Fermi surface?

20. How might the Fermi surface die?

21. Electronic structure at criticality: ``Critical Fermi surface”

22. Why a critical Fermi surface?

23. Evolution of single particle gap

24. Why a critical Fermi surface? Evolution of momentum distribution

25. Killing a Fermi surface

26. Some obvious consequences/questions

27. Scaling phenomenology at a quantum critical point with a
critical Fermi surface?

28. Critical Fermi surface: scaling for single particle physics

29. New possibility: angle dependent exponents

30. Leaving the critical point

32. Implications of angle dependent exponents

33. Finite T crossovers

34. Summary
A Fermi surface may die through a second order phase transition -at the critical point the Landau quasiparticle is destroyed but the Fermi surface is preserved ( the `critical Fermi surface’)
=> non-fermi liquid
Presence of critical fermi surface will change the scaling phenomenology associated with universal critical singularities.
Concrete model calculations with a critical Fermi surface exist
Future – many challenges
Tests of scaling in experiments
Calculational framework?