Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userSimultaneous Measurement of Resistively and Optically Detected Nuclear Magnetic Resonance in the $ u=2/3$ Fractional Quantum Hall Regime
61
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
We observe nuclear magnetic resonance (NMR) in the fractional quantum Hall regime at Landau level filling factor $ u=2/3$ from simultaneous measurement of longitudinal resistance and photoluminescence (PL). The dynamic nuclear spin polarization is induced by applying a huge electronic current at the spin phase transition point of $ u=2/3$. The NMR spectra obtained from changes in resistance and PL intensity are qualitatively the same; that is, the Knight shift (spin polarized region) and zero-shift (spin unpolarized region) resonances are observed in both. The observed change in PL intensity is interpreted as a consequence of the trion scattering induced by polarized nuclear spins. We conclude that both detection methods probe almost the same local phenomena.
rate research
Read More
Nuclear electric resonance (NER) is based on nuclear magnetic resonance mediated by spatial oscillations of electron spin domains excited by a radio frequency (RF) electric field, and it allows us to investigate the spatial distribution of the nuclear spin polarization around domain walls (DWs). Here, NER measurements were made of the dynamic nuclear spin polarization (DNP) at the spin phase transition of the fractional quantum Hall state at a Landau level filling factor of $ u=2/3$. From the RF pulse power and pulse duration dependence of the NER spectrum, we show that the DNP occurs only within $sim 100$ nm around DWs, and that it does not occur in DWs. We also show that DWs are pinned by the hyperfine field from polarized nuclear spins.
We report on magnetotransport measurements of multi-terminal suspended graphene devices. Fully developed integer quantum Hall states appear in magnetic fields as low as 2 T. At higher fields the formation of longitudinal resistance minima and transverse resistance plateaus are seen corresponding to fractional quantum Hall states, most strongly for { u}= 1/3. By measuring the temperature dependence of these resistance minima, the energy gap for the 1/3 fractional state in graphene is determined to be at ~20 K at 14 T.
New low-lying excitations are observed by inelastic light scattering at filling factors $ u=p/(phi p pm 1)$ of the fractional quantum Hall regime with $phi=4$. Coexisting with these modes throughout the range $ u leq 1/3$ are $phi=2$ excitations seen at 1/3. Both $phi=2$ and $phi=4$ excitations have distinct behaviors with temperature and filling factor. The abrupt first appearance of the new modes in the low energy excitation spectrum at $ u lesssim 1/3$ suggests a marked change in the quantum ground state on crossing the $phi=2 to phi=4$ boundary at $ u = 1/3$.
Strong resonant enhancements of inelastic light scattering from the long wavelength inter-Landau level magnetoplasmon and the intra-Landau level spin wave excitations are seen for the fractional quantum Hall state at $ u = 1/3$. The energies of the sharp peaks (FWHM $lesssim 0.2meV$) in the profiles of resonant enhancement of inelastic light scattering intensities coincide with the energies of photoluminescence bands assigned to negatively charged exciton recombination. To interpret the observed enhancement profiles, we propose three-step light scattering mechanisms in which the intermediate resonant transitions are to states with charged excitonic excitations.
We observe geometric resonance features of composite fermions on the flanks of the even denominator { u} = 1/2 fractional quantum Hall state in high-mobility two-dimensional electron and hole systems confined to wide GaAs quantum wells and subjected to a weak, strain-induced, unidirectional periodic potential modulation. The features provide a measure of how close to { u} = 1/2 the system stays single-component and supports a composite fermion Fermi sea before transitioning into a { u} = 1/2 fractional quantum Hall state, presumably the two-component {Psi}331 state.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
