The fractional quantum Hall (FQH) effect at filling factor ν = 5/2 has recently come under close scrutiny, as its ground state may possess quasi-particle excitations obeying nonabelian statistics, a property sought for topologically protected operations. However, microscopic origin remains unknown, and candidate model wave functions include those with undesirable abelian statistics. We report direct measurements of the electron spin polarization FQH using resistively detected nuclear...

In 2005, Kane and Mele [Phys. Rev. Lett. 95, 226801 (2005)PRLTAO0031-900710.1103/PhysRevLett.95.226801] predicted that at sufficiently low energy, graphene exhibits a topological state of matter with an energy gap generated by the atomic spin-orbit interaction. However, this intrinsic has not been measured to date. Letter, we exploit chirality low-energy states resolve gap. We probe spin experimentally employing temperature microwave excitation in resistively detected electron-spin resonance...

Any departure from graphene's flatness leads to the emergence of artificial gauge fields that act on motion Dirac fermions through an associated pseudomagnetic field. Here, we demonstrate tunability strong in nonlocal experiments using a large planar graphene sheet conforms deformation piezoelectric layer by surface acoustic wave. The wave induces longitudinal and giant synthetic Hall voltage absence external magnetic fields. superposition potential conventional can annihilate sample's...

We have investigated the tunneling properties of an electron double quantum well system where lowest Landau level each is half filled. This expected to be a Bose condensate excitons. Our four-terminal dc measurements reveal nearly vanishing interlayer voltage and existence critical currents Icritical which depend on strength state.

Abstract MoS 2 has recently emerged as a promising material for enabling quantum devices and spintronic applications. In this context, an improved physical understanding of the g -factor depending on device geometry is great importance. Resistively detected electron spin resonance (RD-ESR) could be employed to determine in micron-scale However, its application RD-ESR studies have been limited by Schottky or high-resistance contacts . Here, we exploit naturally n-doped few-layer with ohmic...

The effect of tunneling on the transport properties quantum Hall double layers in regime excitonic condensate at a total filling factor one is studied counterflow experiments. If tunnel current I smaller than critical I{C}, large and effectively shorting two layers. For I>I{C} becomes negligible. Surprisingly, transition between regimes has only minor impact features filling-factor state as observed magnetotransport, but currents exceeding I{C} resistance along increases rapidly.

A prominent manifestation of the competition between repulsive and attractive interactions acting on different length scales is self-organized ordering electrons in a stripelike fashion material systems such as high-T_{c} superconductors. Such stripe phases are also believed to occur two-dimensional electron exposed perpendicular magnetic field, where they cause strong anisotropy transport. The addition an in-plane field even enables us expel fractional quantum Hall states, benefit...

Magnetotransport and drag measurements on a quasi-Corbino two-dimensional electron bilayer at total filling factor of 1 $({\ensuremath{\nu}}_{T}=1)$ reveal voltage that is equal in magnitude to the drive as soon two layers begin form expected ${\ensuremath{\nu}}_{T}=1$ exciton condensate. The identity both voltages remains present even elevated temperatures $0.25\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. conductance layer vanishes only limit strong coupling between...

We will discuss the relevant conditions to observe a critical tunneling current [New J. Phys. 10, 045018 (2008)] in electron double-layer systems at total filling factor of 1 and find they are related effective layer separation temperature. Our studies suggest that intensity behavior is also directly linked area sample.

The physics of moiré superlattices and the resulting formation mini-bands in van der Waals materials have opened up an exciting new field condensed matter physics.These systems exhibit a rich phase diagram novel physical phenomena exotic correlated phases that emerge low-dispersing bands.Transition metal dichalcogenides, particular, molybdenum disulfide (MoS 2 ), are potential candidates to extend studies on electronics beyond graphene.Our transport spectroscopy measurements analysis reveal...

The study of nuclear magnetic resonance and spin-lattice relaxation was conducted in an asymmetrically doped to $n\sim1.8\times10^{11}$ cm$^{-2}$ 16 nm AlAs quantum well grown the $[001]$-direction. Dynamic polarization spins due hyperfine interaction resulted so-called Overhauser shift two-dimensional conduction electron spin resonance. maximum shifts achieved experiments are several orders magnitude smaller than GaAs-based heterostructures indicating that is weak. time extracted from decay...

In this study, we demonstrate the possibility to tune Dirac surface states of a three-dimensional topological insulator (TI) by applying external strain single-crystalline Bi2Se3 nanowires (NWs). The NWs were placed over 200 nm deep trenches, which leads significant bending, resulting in tensile at bottom wire and compressive its top surface. By performing low-temperature magnetotransport measurements, able show that TI surfaces under or (ϵ=±0.1%) experience shift ΔE=∓30 meV as compared...

Electron spin resonance (ESR) was studied in an asymmetrically doped 16-nm AlAs quantum well grown the [001] direction. Surprisingly ESR detectable even if magnetic field parallel to surface of two-dimensional system. This allowed us investigate precisely in-plane anisotropy electron $g$ factor. In case aligned along [110] or $[1\overline{1}0]$ crystallographic axes only one peak observed, whereas it tended split into two well-separated peaks when component between these directions. fact...

We present a reliable method to obtain patterned back gates compatible with high mobility molecular beam epitaxy via local oxygen ion implantation that suppresses the conductivity of an 80 nm thick silicon doped GaAs epilayer. Our technique was optimized circumvent several constraints other gating and methods. The ion-implanted surface remains atomically flat which allows unperturbed epitaxial overgrowth. demonstrate practical application this by using magneto-transport spectroscopy on...

Spectra of magnetoplasma excitations have been investigated in two-dimensional electron systems AlAs quantum wells (QWs) different widths. The spectrum has found to change profoundly when the well width becomes thinner than 5.5 nm, indicating a drastic conduction energy spectrum. transformation can be interpreted terms transition from in-plane strongly anisotropic ${X}_{x}\ensuremath{-}{X}_{y}$ valley occupation out-of-plane isotropic ${X}_{z}$ QW plane. Strong enhancement cyclotron...

The spectra of plasma and magnetoplasma excitations in a two-dimensional system anisotropic heavy fermions are investigated. spectrum microwave absorption by disklike samples stressed AlAs quantum wells at low electron densities shows two resonances separated frequency gap. These correspond to mass principle values $(1.10\ifmmode\pm\else\textpm\fi{}0.05){m}_{0}$ $(0.20\ifmmode\pm\else\textpm\fi{}0.01){m}_{0}$. observed results the case single valley strongly Fermi surface. It is established...

Abstract Surface acoustic waves, the microcosmic cousins of seismic can be generated and precisely controlled on a microscopic scale by applying periodic electrical signal to piezoelectric substrate. Harnessing exploring their interactions with two-dimensional van der Waals (vdW) systems opens new frontiers in materials science engineering. As part special issue these guided elastic waves for hybrid nano- quantum technologies, our review highlights work focusing acoustically-induced...

Studies of spin degrees freedom near odd-integer filling $\ensuremath{\nu}=3$ in the second Landau level have engendered conflicting accounts properties this regime. Using resistively detected NMR as a probe local density, we explore nature ground state quantum Hall regime $\ensuremath{\nu}=3$. Our Knight shift measurements reveal anomalies spectral line shapes $\ensuremath{\nu}=3$, which demonstrate presence solid phases formed from charged quasiparticles, with maximal polarization (i.e.,...

We present a gating scheme to separate even strong parallel conductance from the magneto-transport signatures and properties of two-dimensional electron system. By varying density in conducting layer, we can study impact mobile charge carriers vicinity dopant layer on It is found that indeed capable screen remote ionized impurity potential fluctuations responsible for fragility fractional quantum Hall states.

The low-lying states of graphene contain exciting topological properties that depend on the interplay different symmetry-breaking terms. corresponding energy gaps remained unexplored until recently due to low-energy scale terms involved (few tens $\ensuremath{\mu}\mathrm{eV}$). These include sublattice splitting, Rashba coupling, and intrinsic spin-orbit whose balance determines properties. In this work, we unravel contributions arising from spin orbit splitting in hexagonal boron-nitride....

The spin resonance of two-dimensional (2D) electrons confined in a high-quality 4.5-nm AlAs quantum well was studied the regime integer Hall effect. electron $g$-factor extracted from magnetic field position at fixed microwave frequency demonstrated strong nonlinear dependence on with discontinuities around even filling factors. value tended to increase decrease each odd filling. Furthermore, exactly factor $\ensuremath{\nu}$ turned out be dependent $\ensuremath{\nu}$, suggesting...

We present an experimental study of the scattering mechanisms in a two-dimensional electron system which is either fully induced by field effect or resulting from remote doping. The quality criteria---the mobility, quantum time, and number development certain fractional Hall states---are analyzed compared. By eliminating off ionized impurities (RI) undoped systems, we can identify density regimes most susceptible to RI their impact on formation states.

Topological phenomena in two-dimensional materials are characterized by an electrical conductivity that is restricted to the edges of a sample. A heterostructure semiconductors indium arsenide and gallium antimonide, InAs/GaSb, can be quantum spin Hall insulator (QSHI), which exhibits spin-resolved channels at but has insulating bulk. The QSHI linked nontrivial inverted band structure emerges only for certain thicknesses InAs GaSb layers. Here, authors have exposed InAs/GaSb samples variable...