Few-Body Insights Into the Quantum Hall Problem

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Abstract

This talk will summarize insights that emerge from theoretically treating a finite number of (3-8) electrons confined to a two-dimensional plane with a magnetic field oriented transversely.  This is the prototype system of strongly-correlated electrons in condensed matter physics, which gives rise to phenomena such as the fractional quantum Hall effect, where certain combinations of electron density and magnetic field strength (filling fractions) exhibit intriguing features in their resistivity.  Instead of formulating this theoretical problem in the usual framework using independent electron coordinates, we treat it in collective hyperspherical coordinates, which are particularly well-suited to describing nonperturbative behavior of the electron conglomerate as a whole.[1]  A number of insights have emerged from this way of treating the problem, such as an observation that one coordinate of the system, the hyperradius, is quite accurately separable from the other degrees of freedom.  Another observation from our analysis is that the degree of exceptional degeneracy in the non-interacting electron system often correlates with the filling fractions where the famous Laughlin-type or composite-fermion-type states occur experimentally.  Wild, unrestrained speculations on future directions for this line of research will be offered.

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References

[1] K.M. Daily, R.E. Wooten, and Chris H. Greene, Hyperspherical theory of the quantum Hall effect: The role of exceptional degeneracy, Phys. Rev. B 92, 125427-1 to -16 (2015). 10.1103/PhysRevB.92.125427

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Researchers should cite this work as follows:

  • (2016), "Few-Body Insights Into the Quantum Hall Problem," https://nanohub.org/resources/23341.

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Location

Physics, Room 203, Purdue University, West Lafayette, IN

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Few-Body Insights Into the Quantum Hall Problem
  • Few-body insights into the Quantum Hall problem 1. Few-body insights into the Qua… 0
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  • Untitled: Slide 2 2. Untitled: Slide 2 127.52752752752754
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  • From few to many – How can we understand the universality? 3. From few to many – How can w… 135.43543543543544
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  • Fermi Systems in Nature 4. Fermi Systems in Nature 215.51551551551552
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  • The Fractional Quantum Hall Effect 5. The Fractional Quantum Hall Ef… 292.85952619285956
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  • Motivations 6. Motivations 350.81748415081751
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  • few-body hyperspherical toolkit 7. few-body hyperspherical toolki… 542.04204204204211
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  • Some successes of the adiabatic hyperspherical representation: 8. Some successes of the adiabati… 640.00667334000673
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  • Strategy of Macek's adiabatic hyperspherical representation 9. Strategy of Macek's adiabatic … 718.98565231898567
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  • Joe Macek's (1968 JPB) adiabatic hyperspherical picture 10. Joe Macek's (1968 JPB) adiabat… 1044.1107774441109
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  • Untitled: Slide 11 11. Untitled: Slide 11 1088.8888888888889
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  • Universality, from nuclear scale energies to the chemical 12. Universality, from nuclear sca… 1152.8194861528195
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  • Here is our Hamiltonian, which we recast into hyperspherical coordinates in the usual way: 13. Here is our Hamiltonian, which… 1214.5812479145814
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  • Table 6 14. Table 6 1250.6172839506173
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  • 15. "Critical number for bosonic c… 1302.7360694027361
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  • Effect of renormalization 16. Effect of renormalization 1310.2769436102769
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  • Back to the quantum Hall problem: 17. Back to the quantum Hall probl… 1369.2025358692026
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  • Potential energy of just 1 2D electron in a B-field 18. Potential energy of just 1 2D … 1452.7861194527861
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  • Now go to collective N-body coordinates 19. Now go to collective N-body co… 1494.7614280947614
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  • Hypersperical coordinate transformation 20. Hypersperical coordinate trans… 1609.5762429095762
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  • In hyperspherical coordinates: 21. In hyperspherical coordinates: 1640.9409409409409
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  • Now apply this adiabatic hyperspherical method to the quantum Hall problem 22. Now apply this adiabatic hyper… 1734.7013680347016
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  • Potential energy curves for N noninteracting electrons in 2D in a B-field as a function of the hyperradius 23. Potential energy curves for N … 1828.1948615281949
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  • K=-M=8 3 particles 24. K=-M=8 3 particles 1921.187854521188
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  • K=-M=9 3 particles 25. K=-M=9 3 particles 1962.8962295628962
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  • K=-M=10 3 particles 26. K=-M=10 3 particles 2012.9462796129465
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  • The Laughlin 1/3 state is one of these, having K = -M =3N(N-1)/2 27. The Laughlin 1/3 state is one … 2164.9983316649982
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  • Noninteracting states for K=|M|=9,11,13,15, 28. Noninteracting states for K=|M… 2286.252919586253
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  • Now look at some quantitative measures of accuracy 29. Now look at some quantitative … 2293.5602268935604
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  • TESTING ADIABATICITY 30. TESTING ADIABATICITY 2335.3019686353023
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  • The composite-fermion view 31. The composite-fermion view 2462.2288955622289
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  • Semiconductor quantum dots in high magnetic fields 32. Semiconductor quantum dots in … 2542.475809142476
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  • Filling factor, n  33. Filling factor, n  2565.765765765766
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  • Potential energy landscape at fixed hyperradius for 6 particles, 34. Potential energy landscape at … 2576.50984317651
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  • Noninteracting Quantum fermions 35. Noninteracting Quantum fermion… 2653.7203870537205
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  • How does fixed-node Monte Carlo work for fermions? 36. How does fixed-node Monte Carl… 2716.2829496162831
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  • Minimum quantum Coulomb potential eigenvalues 37. Minimum quantum Coulomb potent… 2767.5342008675343
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  • Eigenenergies for 4 particles after quantizing also in the hyperradius R 38. Eigenenergies for 4 particles … 2811.5115115115118
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  • K= -M=9 for N=3 39. K= -M=9 for N=3 2816.8501835168504
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  • Next: an exploration of the role of DEGENERACY 40. Next: an exploration of the ro… 2818.8188188188187
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  • On the role of exceptional degeneracy 41. On the role of exceptional deg… 2914.2142142142143
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  • Connection between the high relative degeneracy states 42. Connection between the high re… 2973.7070403737071
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  • Devil's staircase 43. Devil's staircase 3062.92959626293
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  • Connections between hyperspherical and conventional filling factors 44. Connections between hyperspher… 3101.6683350016683
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  • Energy vs. Magnetic field 45. Energy vs. Magnetic field 3126.2929596262929
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  • Energy spectrum after solving for the hyperradial vibrational degree of freedom, as a function of magnetic field. 46. Energy spectrum after solving … 3130.1968635301969
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  • 47. "Devil's Staircase" 3134.9683016349686
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  • Fractional Quantum Hall Effect of Compositer Fermions 48. Fractional Quantum Hall Effect… 3200.8675342008678
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  • Breathing mode signatures of the Laughlin 1/3 state, a prediction (preliminary): 49. Breathing mode signatures of t… 3211.344678011345
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  • What have we learned 50. What have we learned 3278.2782782782783
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  • Other directions to understand: 51. Other directions to understand… 3396.3630296963634
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  • Conclusions 52. Conclusions 3437.6710043376711
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  • Demo 53. Demo 3445.8458458458458
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