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Motivated by a recent experiment of Willett et al. [Phys. Rev. Lett. 78, 4478 (1997)], we employ semiclassical composite-fermion theory to study the effect of a periodic density modulation on a quantum Hall system near Landau level filling…
Motivated by the experimental results of Willett et al [Phys.Rev. Lett., {\bf 78}, 4478 (1997)] we develop a magneto-transport theory for the response of a two dimensional electron gas (2DEG) in the Fractional Quantum Hall Regime near…
The enigmatic even-denominator fractional quantum Hall state at Landau level filling factor $\nu=5/2$ is arguably the most promising candidate for harboring Majorana quasi-particles with non-Abelian statistics and thus of potential use for…
Using a 50-nm width, ultra-clean GaAs/AlGaAs quantum well, we have studied the Landau level filling factor $\nu = 5/2$ fractional quantum Hall effect in a perpendicular magnetic field $B \sim$ 1.7 T and determined its dependence on tilted…
A semiclassical theory for magnetotrasport in a quantum Hall system near filling factor $\nu = 1/2 $ based on the Composite Fermions physical picture is used to analyze the effect of local flattening of the Composite Fermion Fermi surface…
Using acoustic method we study dependences of transverse AC conductance, $\sigma (\omega)$, on magnetic field, temperature and the amplitude of AC electric field in a wide (75 nm) quantum well (QW) structure focusing on the vicinity of the…
The 5/2 fractional quantum Hall effect in the second Landau level of extremely clean two-dimensional electron gases has attracted much attention due to its topological order predicted to host quasiparticles that obey non-Abelian quantum…
By strictly adhering to the microscopic theory of composite fermions for the Landau-level filling fractions nu_e = p/(2 p + 1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by Willett…
By strictly adhering to the microscopic theory of composite fermions (CFs) for the Landau-level filling fractions \nu_e = p/(2 p + 1), we reproduce, with remarkable accuracy, the surface-acoustic-wave (SAW)-based experimental results by…
The interaction of surface acoustic waves (SAW) with $p$-type Si/Si$_{0.87}$Ge$_{0.13}$ heterostructures has been studied for SAW frequencies of 30-300 MHz. For temperatures in the range 0.7$<T<$1.6 K and magnetic fields up to 7 T, the SAW…
The pairing of composite fermions (CFs), electron-flux quasi-particles, is commonly proposed to explain the even-denominator fractional quantum Hall state observed at $\nu=5/2$ in the first excited ($N=1$) Landau level (LL) of a…
A standing problem in low dimensional electron systems is the nature of the 5/2 fractional quantum Hall state: its elementary excitations are a focus for both elucidating the state's properties and as candidates in methods to perform…
We study the effect of a periodic density modulation on surface acoustic wave (SAW) propagation along a 2D electron gas near Landau level filling $\nu=1/2$. Within the composite fermion theory, the problem is described in terms of fermions…
We propose that a new state with a fully gapless Fermi surface appears in quasi-2D multiband superconductors in magnetic field applied parallel to the plane. It is characterized by a paramagnetic moment caused by a finite density of states…
The propagation of a surface acoustic wave (SAW) on GaAs/AlGaAs heterostructures is studied in the case where the two-dimensional electron gas (2DEG) is subject to a strong magnetic field and a smooth random potential with correlation…
In a recent paper [Phys.Rev.Lett. 82, 3665 (1999)], magnetic field driven spin transitions in fractional quantum Hall (FQH) states were reported, and in particular, at filling factors 2/3 and 2/5, weak features were observed at half…
We report extensive measurements of quantum oscillations in the normal state of the Fe-based superconductor LaFePO, (Tc ~ 6 K) using low temperature torque magnetometry and transport in high static magnetic fields (45 T). We find that the…
It is demonstrated that an understanding of the 5/2 fractional quantum Hall effect can be achieved within the composite fermion theory without appealing to the Pfaffian wave function. The residual interaction between composite fermions…
We introduce a new generic model of a deformed Composite Fermion-Fermi Surface (CF-FS) for the Fractional Quantum Hall Effect near $/nu=1/2$ in the presence of a periodic density modulation. Our model permits us to explain recent Surface…
We report magneto-transport measurements in wide GaAs quantum wells with tunable density to probe the stability of the fractional quantum Hall effect at filling factor $\nu = $ 5/2 in the vicinity of the crossing between Landau levels (LLs)…