Electrical transport near a pair-breaking superconductor-metal quantum phase transition

Transcription

1 Electrical transport near a pair-breaking superconductor-metal quantum phase transition Emily Dunkel (Harvard) Joel Moore (Berkeley) Daniel Podolsky (Berkeley) Subir Sachdev (Harvard) Ashvin Vishwanath (Berkeley) Philipp Werner (ETH) Matthias Troyer (ETH) Physical Review Letters 92, (2004) Physical Review B 73, (2006) cond-mat/ See also talk by Daniel Podolsky, N , Wed 9:12 AM Talk online at

2 T T c Metal Superconductor α c α

3 T T c Metal Superconductor α c α

4 Y. Liu, Yu. Zadorozhny, M. M. Rosario, B. Y. Rock, P. T. Carrigan, and H. Wang, Science 294, 2332 (2001).

5

6 I. Theory for the superconductor-metal quantum phase transition

7 Computation of fluctuation conductivity in metal at low temperatures T T c Superconductor Metal α c α

8 Computation of fluctuation conductivity in metal at low temperatures T T c Superconductor Metal α c α

9 Computation of fluctuation conductivity in metal at low temperatures T T c Superconductor Metal α c α

10 Computation of fluctuation conductivity in metal at low temperatures T T c Superconductor Metal α c α

11 Theory for quantum-critical region, and beyond T T c Quantum critical Superconductor Metal α c α

12 Theory for quantum-critical region, and beyond T T c Quantum critical Superconductor Metal α c α In one dimension, theory reduces to the Langer-Ambegaokar- McCumber-Halperin theory (Model A dynamics), near mean-field T c

13 Role of charge conservation in quantum critical theory 2 (related to the question of why dissipation is not ω q ) Dynamics of quantum theory (and model A) does not conserve total charge. Analogous the Fermi-liquid/spin-density-wave transition (Hertz theory), where dynamics of critical theory does not conserve total spin.

14 Role of charge conservation in quantum critical theory 2 (related to the question of why dissipation is not ω q ) Dynamics of quantum theory (and model A) does not conserve total charge. Analogous the Fermi-liquid/spin-density-wave transition (Hertz theory), where dynamics of critical theory does not conserve total spin. Cooper pairs (SDW) fluctuations decay into fermionic excitations at a finite rate, before any appreciable phase precession due to changes in chemical potential (magnetic field).

15 II. Quantum criticality in d=1

16 Theory for quantum-critical region, and beyond in d=1 T T c Quantum critical Superconductor Metal α c α

17 Theory for quantum-critical region, and beyond in d=1 T T c Quantum critical Superconductor Metal α c α

18 Theory for quantum-critical region, and beyond in d=1 T T c Quantum critical Superconductor Metal α c α

19 III. Nanowires near the superconductor-metal quantum critical point

20 Nanowires near the quantum critical point in d=1 T T c Quantum critical Superconductor Metal α c α

21 Effect of the leads

22 Large n computation of conductance

23 Quantum Monte Carlo and large n computation of d.c. conductance

24 IV. Quantum criticality in d=2

25 Theory for quantum-critical region, and beyond in d=2

26 Locus of points with U/R constant

27 Locus of points with U/R constant

28 Locus of points with U/R constant

29 Conclusions Universal transport in in wires near the the superconductor-metal transition Theory includes contributions from thermal and quantum phase slips ---- reduces to to the the classical LAMH theory at at high temperatures Sensitivity to to leads should be be a generic feature of of the the ``coherent transport regime of of quantum critical points. Complete computation of of electrical transport in in d=2 to to leading logarithmic accuracy.