Electron spin relaxation in semiconducting carbon nanotubes: the role of hyperfine interaction

The time-window for processing electron spin information (spintronics) in solid-state quantum electronic devices is determined by the spin-lattice (T1) and spin-spin (T2) relaxation times of electrons. Minimising the effects of spin-orbit coupling and the local magnetic contributions of neighbouring atoms on T1 and T2 at room temperature remain substantial challenges to practical spintronics. Here, we report a record-high conduction electron T1=T2 of 175 ns at 300 K in 37 nm ...

Relaxation of conduction electron spins in a semiconductor owing to the hyperfine interaction with spin-1/2 nuclei, in zero applied magnetic field, is investigated. We calculate the electron spin relaxation time scales, in order to evaluate the importance of this relaxation mechanism. Master equations for the electron spin density matrix are derived and solved. Polarized nuclear spins can be used to polarize the electrons in spintronic devices.

We review the theoretical description of spin-orbit scattering and electron spin resonance in carbon nanotubes. Particular emphasis is laid on the effects of electron-electron interactions. The spin-orbit coupling is derived, and the resulting ESR spectrum is analyzed both using the effective low-energy field theory and numerical studies of finite-size Hubbard chains and two-leg Hubbard ladders. For single-wall tubes, the field theoretical description predicts a double peak s...

Hyperfine interaction (HF) is of key importance for the functionality of solid-state quantum information processing, as it affects qubit coherence and enables nuclear-spin quantum memories. In this work, we complete the theory of the basic hyperfine interaction mechanisms (Fermi contact, dipolar, orbital) in carbon nanotube quantum dots by providing a theoretical description of the orbital HF. We find that orbital HF induces an interaction between the nuclear spins of the nan...

We present formulas for the nuclear and electronic spin relaxation times due to the hyperfine interaction for nanostructed systems and show that the times depend on the square of the local density of electronic states at the nuclear position. A drastic sensitivity (orders of magnitude) of the electronic and nuclear spin coherence times to small electric fields is predicted for both uniformly distributed nuclear spins and for $\d$-doped layers of specific nuclei. This sensitiv...

An effective spin relaxation mechanism that leads to electron spin decoherence in a quantum dot is proposed. In contrast to the common calculations of spin-flip transitions between the Kramers doublets, we take into account a process of phonon-mediated fluctuation in the electron spin precession and subsequent spin phase diffusion. Specifically, we consider modulations in the longitudinal g-factor and hyperfine interaction induced by the phonon-assisted transitions between th...

We develop a quantum theory for a variety of nuclear spin dynamics such as dephasing, relaxation, squeezing, and narrowing due to the hyperfine interaction with a generic, dissipative electronic system. The first-order result of our theory reproduces and generalizes the nonlinear Hamiltonian for nuclear spin squeezing [M. S. Rudner, Phys. Rev. Lett. 107, 206806 (2011)]. The second-order result of our theory provides a good explanation to the experimentally observed $^{13}$C n...

Following the recent successful formation and manipulation of entangled $C^{13}$ atoms on the surface of Diamond we calculate the decoherence of the electron spin polarization in Diamond via a nonperturbative treatment of the time-dependent Greens function of the Central-Spin model, describing the phonon and Hyperfine couplings of the electron to a bath of $C^{13}$ atoms, for arbitrary initial polarizations, applied field strengths, and for up to eight entangled $C^{13}$ atom...

On the basis of the spin-polarized density functional theory calculations, we demonstrate that partially-open carbon nanotubes (CNTs) observed in recent experiments have rich electronic and magnetic properties which depend on the degree of the opening. A partially-open armchair CNT is converted from a metal to a semiconductor, and then to a spin-polarized semiconductor by increasing the length of the opening on the wall. Spin-polarized states become increasingly more stable t...

A chapter contribution to book: "Handbook of Spin Transport and Magnetism", ed. by Evegeny Y. Tsymbal and Igor Zutic (Chapman & Hall/CRC, 2011) http://www.crcpress.com/product/isbn/9781439803776 .