Coupling of Electron Spin Dynamics and Nanomechanical Motion in Carbon Nanotubes

By Mark Rudner

Niels Bohr Institute, Copenhagen, Denmark

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Abstract

Due to their low masses and high stiffnesses, nanostructures made out of atomically-thin carbon- based materials such as graphene and carbon nanotubes (CNTs) feature high mechanical oscillation frequencies and large zero-point vibration amplitudes. These properties open many avenues for exploring both fundamental phenomena and potential applications based on the coupling of nanomechanical and electronic degrees of freedom. The recently discovered strong spin-orbit coupling in CNTs provides an intrinsic coupling between electron spins and flexural motion of the nanotube. For a long nanotube with a quasi-continuous phonon spectrum, we show that this coupling gives rise to a dramatic enhancement of the electron spin relaxation rate near a level crossing in the Zeeman spectrum of a few-electron nanotube quantum dot spin qubit, as observed in recent experiments. For a short suspended nanotube with well-separated discrete phonon modes, this system can provide a natural solid state realization of the Jaynes-Cummings model of quantum optics. Our estimates indicate that, with currently achievable experimental parameters, the strong coupling regime of coherent spin-phonon exchange is within reach. Detection schemes and potential applications will be discussed.

Bio

After earning his PhD in Physics at the Massachusetts Institute of Technology (2008), he spent 3 years as a postdoctoral fellow at Harvard University. In 2011 he joined the faculty of Ohio State University as an Assistant Professor, before moving to NBIA in the fall of 2012. Mark has worked on a wide range of topics, including electron- nuclear spin dynamics in semiconductor quantum dots, electron transport and photothermal effects in graphene, spin-orbit coupling in carbon nanotubes, and topological phenomena in dissipative and periodically-driven systems.

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Researchers should cite this work as follows:

  • Mark Rudner (2014), "Coupling of Electron Spin Dynamics and Nanomechanical Motion in Carbon Nanotubes," https://nanohub.org/resources/21268.

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Birck Nanotechnology Center, Rm 1001, Purdue University, West Lafayette, IN

Coupling of Electron Spin Dynamics and Nanomechanical Motion in Carbon Nanotubes
  • Coupling of spin and nanomechanical motion in carbon nanotubes Mark Rudner Niels Bohr Institute 1. Coupling of spin and nanomecha… 0
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  • Understand,control,and exploit electronic properties beyond charge 2. Understand,control,and exploit… 77.21054387721054
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  • Vibrant research community in Copenhagen 3. Vibrant research community in … 220.28695362028697
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  • Outline 4. Outline 296.46312979646314
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  • In nature,carbon comes in many forms 5. In nature,carbon comes in many… 341.10777444110778
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  • Graphite:stacked 2D sheets of carbon 6. Graphite:stacked 2D sheets of … 396.16282949616283
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  • Graphene:a single atomic plane of carbon 7. Graphene:a single atomic plane… 438.73873873873873
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  • Conduction and valence bands touch at Fermi Level 8. Conduction and valence bands t… 492.59259259259261
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  • Nanotube formed by 9. Nanotube formed by"rolling up"… 546.21287954621289
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  • States nearKand K carry opposite circulating currents kz 10. States nearKand K carry opposi… 781.54821488154823
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  • Electrons confined to quantum dots via electrostatic gates 11. Electrons confined to quantum… 894.1274607941275
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  • Degeneracy lifted in applied field by orbital,spin moments 12. Degeneracy lifted in applied … 1005.3053053053053
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  • Degeneracy partially lifted at B = 0 by spin-orbit coupling 13. Degeneracy partially lifted at… 1095.1284617951285
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  • Relativity:orbiting electron'sees' magnetic field from nucleus 14. Relativity:orbiting electron's… 1345.0450450450451
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  • (Atomic spin orbit) + (nanotube curvature) = sizable effect 15. (Atomic spin orbit) + (nanotub… 1464.7981314647982
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  • Spin-orbit coupling 16. Spin-orbit coupling"locks" spi… 1597.9312645979314
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  • Nanotube supports many vibrational modes 17. Nanotube supports many vibrati… 1784.0840840840842
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  • In flexural mode,local tube axis direction fluctuates 18. In flexural mode,local tube a… 1802.1688355021688
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  • Outline 19. Outline 1869.2025358692026
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  • Observation:minimum in spin lifetime 20. Observation:minimum in spin li… 2050.6172839506175
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  • Through spin-orbit interaction,spin couples to local direction of tube axis 21. Through spin-orbit interaction… 2234.6012679346013
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  • Spin couples to phonons through deflections 22. Spin couples to phonons throug… 2341.9085752419087
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  • Calculate spin relaxation rate from Fermi's Golden Rule 23. Calculate spin relaxation rate… 2377.1438104771437
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  • Vibration amplitudes grow large for long wavelengths 24. Vibration amplitudes grow larg… 2388.4884884884887
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  • Relaxation rate shows divergence at small energy transfer 25. Relaxation rate shows divergen… 2561.4280947614284
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  • Compare with 26. Compare with"usual" deformatio… 2627.4274274274276
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  • Outline 27. Outline 2717.9846513179846
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  • Ultraclean suspended CNTs act as 28. Ultraclean suspended CNTs act … 3006.43977310644
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  • Outlook:strong (coherent) coupling regime within reach D 29. Outlook:strong (coherent) coup… 3126.1261261261261
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  • Coupling leads to enhancement of transport near resonance 30. Coupling leads to enhancement … 3418.5185185185187
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  • Pulsed gate measurements may reveal coherent oscillations 31. Pulsed gate measurements may r… 3491.5582248915584
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  • Sense motion of CNT via coupling to microwave cavity? Concern:typical vibration amplitudes in 1-10 pm range Possible solution:use large electron number to get sizable dipole moment 32. Sense motion of CNT via coupli… 3506.1394728061396
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  • Quantum dots in suspended CNTs might make good qubits 33. Quantum dots in suspended CNTs… 3537.4040707374043
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