Download presentation

Presentation is loading. Please wait.

Published byEthan Cunningham Modified over 3 years ago

1
Quantum Nucleation of Charge & Flux Solitons John H. Miller, Jr. A. I. Wijesinghe, Z. Tang, & A. M. Guloy Dept. of Physics, Dept. of Chemistry, & Texas Center for Superconductivity University of Houston jhmiller@uh.edu ECRYS - 2011 August 16, 2011

2
Tunneling of BEC Solitons (Hulet group) 2 Bright matter wave solitons 10 5 7 Li atoms x 13,000m e M > 10 9 m e Macroscopic wavefunctions tunnel through optical barrier (w/ transmitted & reflected components). Tunneling probability: Agrees w/ experiment only if m & V taken to be single atom quantities. Hybrid between Josephson tunneling & MQT. BEC soliton = quantum fluid. Quantum fluid: Each particle delocalized over l > interparticle spacing. CDW = quantum fluid: Each e - delocalized over long distances.

3
CDW dielectric response: Classical predictions vs. experiment 3 1.Random pinning model: Littlewood PR B 33 6694 (1986). 2.CF: Coppersmith & Fisher PR A 38 6338 (1988). 3.NM: Narayan & Middleton PR B 49, 244 (1994). 4.ZG: Zettl & Grüner PR B 29 755 (1984); WMG: Wu, Mihaly, & Grüner Solid State Commun. 55 663 (1985). Other ac responses flat below threshold. JHM et al. PR B 31 5229 (1985).

4
Nucleation of Charge of Flux Soliton Pairs Q 0 = 2Ne c, internal field JHM, Ordóñez, Prodan PRL 84 1555 (2000); JHM et al. J. Phys. A 36 9209 (2003); S. Coleman, Ann. Phys. 101, 239 (1976). Magnetic blockade effect for Josephson vortex pair nucleation: = Coulomb blockade threshold. E T Coulomb Blockade << E T Classical Energy difference: Widom & Srivastava, Phys. Lett. 114A, 337 (1986).

5
E T (Coulomb blockade) increases w/ n impurity 5 Coulomb blockade threshold field: E T = Q 0 /2 A = eN c / A Grüner empirical relation emerges naturally! E T = e c n ch ( n ch = N/A, c = condensate fraction) G. Grüner, Rev. Mod. Phys. 60, 1129 (1988). Derived relation for classical depinning field E cl (Grüner): E cl = 4 e c n ch E T (Coulomb blockade) = E cl /4 Expect E T (C.B.) n i 2 for weak pinning.

6
Time Correlated Soliton Tunneling 6 ‘Vacuum angle’: Pinning & electrostatic energy (per chain): JHM, Ordóñez & Prodan PRL 84 1555 (2000). JHM, Cárdenas, et al. J. Phys. A 36 9209 (2003); S. Coleman, Ann. Phys. 101, 239 (1976). Charging energy: Tunneling (‘false vacuum’ decay) when ( or – 2 n > ).

7
7 Explains flat dielectric response u E /u p = 1 u E /u p = 0.6 u E /u p = 0.2 u E /u p = 0.015 JHM, Ordóñez, & Prodan PRL 84 1555 (2000). Ross, Wang, & Slichter PRL 56 663 (1986). = u E /u p

8
8 h /2 e oscillations in CDW magnetoconductance Latyshev et al, PRL 78, 919 (1997). NbSe 3 with columnar defects h / 2e quantum interference in CDW rings. Tsubota et al, Physica B 404 416–418 (2009). (Tanda group, Hokkaido U., Sapporo, Japan) Contrasts w/ h/2Ne prediction (e.g. Bogachek et al, PRB 42, 7614 (1990) ).

9
9 Proposed model to simulate DW dynamics Analogous to time-correlated single-electron tunneling (Averin & Likharev, J. Low T. Phys. 62 345 (1986)) Defining: & yields:

10
Use of probability amplitudes, TDSE 10 Motivated by Feynman Lectures, vol. III treatment of Josephson junction. Introduce field-dependent tunneling Hamiltonian matrix element: Amplitude for density wave to be on branch n: Time-dependent Schrödinger equation = “classical” Eq. of motion. [in][in]

11
Probability amplitudes, TDSE: Results 11

12
Probability amplitudes, TDSE: Results (continued) 12 Solid lines – theory; Dashed Lines - experiment Experimental data – McCarten group, PRB 2000. 9.90 mA 10.89 mA 11.49 mA 11.88 mA

13
Probability amplitudes, TDSE: Results (continued) 13 Dotted lines: J cdw ~ [E E Tm ]exp[ E 0 /E] Thorne, Miller, et al, PRL 55, 1006 (1985)

14
TDSE: Theory vs. Experiment on dV/dI 14 NbSe 3

15
Phase Diagram – Soliton Nucleation vs. Classical Depinning 15 Blue bronze data (Mihaly et al)

16
h/2e Aharonov-Bohm oscillations in CDW rings 16

17
17 Time-varying vector potential Modulates phase of wavefunction TaS 3 – 185 K JHM... Bardeen, PRL 51, 1592 (1983); PRB 31, 5229 (1985); JHM, PhD dissertation (1985). Nonlinear mixing vs. Photon assisted tunneling theory

18
“Bells & whistles:” Model with multiple domains 18

19
Inclusion of nonlinear terms: 19 g’ =.001g’ =.01g’ =.02

20
20 Alternative approach: Use of Probabilities Let p = probability tunnels from branch n to n +1. Then: -

21
Fixed time interval (non-integer # of cycles) used when averaging voltage 21 TheoryExperiment (Cornell group)

22
Thickness dependence of I c in YBCO coated conductors 22 Pair creation current, d > : Effective 2D penetration length:

23
V - I curve of YBCO grain boundary junction 23 Data from R. D. Redwing et al., APL 75, 3171 (1999). Classical RSJ model: Quantum Simulations ( solid lines ) 86 K 82.5K 77.2K 75K 70K

24
Superconducting iron pnictide bi-crystal junction 24 Data from X. Zhang et al., APL 95, 062510 (2009). 4.2 K

25
Broader implications of model 25 Spontaneous CP violation: “ = ” instability e.g. D. Boer, J. K. Boomsma, PRD 78, 054027 (2008). Michel H. G. Tytgat, PRD 61, 114009 (2000). = instabilities have also been proposed for: - Quantum Hall effect - Topological Insulators Quantum cosmology: Quantum creation of universe(s) Phase transitions in the early universe Tunneling of universe small ( 0) cosmological constant e.g. P. J. Steinhardt, N. Turok, Science 312, 1180 (2006).

26
Concluding Remarks 26 Quantum theory is the most ubiquitous, universally applicable theory known to man. The laws of quantum physics govern every system of particles in the universe, & probably the universe as a whole. One of those laws (Murray Gell-Mann’s totalitarian principle) is: “Everything not forbidden is compulsory.”

27
Acknowledgements 27 Previous collaborators: John Tucker, John Bardeen, UIUC Documentary, book: http://1m1f.com/video/OyV8qSwGUHU/Spark-of-Genius-The-Story-of-John-Bardeen-at- the-University-of-Illinois.html Articles about and by John Bardeen: David Pines, Physics Today, April 1992. Proc. Am. Phil. Soc. 153, 287 (2009). John Bardeen, Physics Today, December 1990. Previous collaborators (continued): Emil Prodan (currently at Yeshiva U.), Carlos Ordonez (UH), John McCarten, Amitesh Maiti Current collaborators (UH): Asanga I. Wijesinghe, Zhongjia Tang, Arnold M. Guloy Funding: NIH, Texas: Texas Ctr. for Superconductivity

28
August 16, 201128 ECRYS 2011 jhmiller@uh.edu Thank you!

Similar presentations

OK

Bose-Einstein Condensation and Superfluidity Lecture 1. T=0 Motivation. Bose Einstein condensation (BEC) Implications of BEC for properties of ground state.

Bose-Einstein Condensation and Superfluidity Lecture 1. T=0 Motivation. Bose Einstein condensation (BEC) Implications of BEC for properties of ground state.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on eisenmenger syndrome asd Ppt on conceptual art emphasizes Ppt on object-oriented programming concepts in java Ppt on object-oriented programming polymorphism Ppt on series and parallel circuits video Ppt on magnets and springs Ppt on eye os od Best ppt on body language Ppt on social contract theory of government Ppt on rc phase shift oscillator connections