Electrically Controlled Nuclear Spin Polarization and Relaxation by Quantum-Hall States

Abstract

We investigate interactions between electrons and nuclear spins by using the resistance (R xx ) peak which develops near filling factor ν = 2/3 as a probe. By temporarily tuning ν to a different value, ν temp, with a gate, the R xx peak is shown to relax quickly on both sides of ν temp = 1. This is due to enhanced nuclear spin relaxation by Skyrmions, and demonstrates the dominant role of nuclear spin in the transport anomaly near ν = 2/3. We also observe an additional enhancement in the nuclear spin relaxation around ν = 1/2 and 3/2, which suggests a Fermi sea of partially-polarized composite fermions.

Spin and Charge Ordering in the Quantum Hall Regime

“…3.5). Similar relaxation behavior has been observed before [179,180,189]. It was attributed to the formation of skyrmions in the vicinity of the = 1 IQHS, more precisely, to the presence of the so-called Goldstone mode.…”

“…3.3b). On the other hand, the coexistence of unpolarized and polarized domains at the spin transition was found to facilitate a dynamic nuclear spin polarization when imposing an external current [8,179,180,186,187]. The underlying process can be understood in the following way [6].…”

“…This dynamic term is key to different ways of dynamic nuclear spin polarization, for example by electron spin resonance [176] and optical pumping [177,178]. It also provides an efficient channel for nuclear spin relaxation if the energies of an electronic and nuclear spin flip match [179,180]. The second, static term in equation 3.8 states that a polarized nuclear spin system alters the electronic Zeeman energy.…”

Resistively detected nuclear magnetic resonance via a single InSb two-dimensional electron gas at high temperature

“…Electrical manipulation of individual nuclei of Ga and As has been achieved in a GaAs two-dimensional electron gas (2DEG) by taking advantage of the resistively detected nuclear magnetic resonance (RDNMR), an emerging high-sensitivity NMR technique. [2][3][4][5][6] However, all of these experiments were performed only at millikelvin temperatures. More recently, electrical detection of coherent oscillations of nuclear spins has been realized in the breakdown regime of integer quantum Hall states of the GaAs 2DEG with an operating temperature up to 1.5 K. 7 Control and monitor of spin transfer between electrons and nuclei at elevated temperatures is undoubtedly valuable for practical applications of the nuclear spin based QIP.…”

Transient analysis of oblique Hanle signals observed in GaAs

“…The polarized nuclear spins will, in turn, affect the electron spins by enhancing electron spin relaxation in semiconductors [1]. Several instances of DNP in semiconductors induced by optical means or electrical means have been reported [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. Furthermore, coherent manipulation of nuclear spins, or Rabi oscillation, which is a key factor for nuclear-spin-based qubits, has been demonstrated electrically in GaAs/AlGaAs quantum Hall systems [18][19][20] and optically in GaAs/AlGaAs quantum wells [21,22].…”