A Correlated Phase of Skyrmions Observed in Real Space

We conduct photoluminescence microscopy that is sensitive to both electron and nuclear spin polarization to investigate the changes that occur in the magnetic ordering in the vicinity of the first integer quantum Hall state in a GaAs 2D electron system (2DES). We observe a discontinuity in the electron spin polarization and nuclear spin longitudinal relaxation time which heralds […]

Spin helix dynamics

Electron spin transport and dynamics are investigated in a single, high-mobility, modulation-doped, GaAs quantum well using ultrafast two-color Kerr-rotation microspectroscopy, supported by qualitative kinetic theory simulations of spin diffusion and transport. Evolution of the spins is governed by the Dresselhaus bulk and Rashba structural inversion asymmetries, whichmanifest as an effectivemagnetic field that can be extracted directly from the experimental […]

Transmission and reflection of charge-density wave packets

Quantum energy teleportation (QET) is a proposed protocol related to quantum vacuum. The edge channels in a quantum Hall system are well suited for the experimental verification of QET. For this purpose, we examine a charge-density wave packet excited and detected by capacitively coupled front gate electrodes. We observe the waveform of the charge packet, […]

Nuclear spins detected by microscope

This work introduces a high-resolution, high-sensitivity method of imaging nuclear polarization by combining photoluminescence spectroscopy with a magnetic resonance technique similar to what is used in medical MRI. The stage for this research was the long-studied fractional quantum Hall liquid in which abrupt transitions occur in the degree to which electron spins are polarized. When […]

The direct-to-indirect band gap crossover in two-dimensional van der Waals crystals

The electronic band structure of van der Waals (vdW) layered crystals has properties that depend on the composition, thickness and stacking of the component layers. Here we use density functional theory and high field magneto-optics to investigate the metal chalcogenide InSe, a recent addition to the family of vdW layered crystals, which transforms from a […]

Hyperfine-controlled domain-wall motion observed in real space and time

Recently, a number of experimental methods have been found by which magnetic domains can be controlled and made to propagate through a host material. Theoretical schemes have also been devised to cleverly manipulate magnetic domains in space in order to enable new logic and memory devices with improved performance. Efforts to better understand the physics […]

Enhanced spin-polarization lifetimes

Enhanced spin-polarization lifetimes in a two-dimensional electron gas in a gate-controlled GaAs quantum well Exciton, trion, and electron spin dynamics in a 20-nm-wide modulation-doped GaAs single quantum well are investigated using resonant ultrafast two-color Kerr rotation spectroscopy. Excitons and trions are selectively detected by resonant probe pulses while their relative spectral weight is controlled by […]

Quantum state tomography

Quantum state tomography of large nuclear spins in a semiconductor quantum well: Optimal robustness against errors as quantified by condition numbers We discuss methods of quantum state tomography for solid-state systems with a large nuclear spin I=3/2 in nanometer-scale semiconductors devices based on a quantum well. Due to quadrupolar interactions, the Zeeman levels of these […]

Quantum energy teleportation without a limit of distance

Quantum energy teleportation (QET) is, from the operational viewpoint of distant protocol users, energy transportation via local operations and classical communication. QET has various links to fundamental research fields including black-hole physics, the quantum theory of Maxwell’s demon, and quantum entanglement in condensed-matter physics. However, the energy that has been extracted using a previous QET […]

Real-space imaging of fractional quantum Hall liquids

Electrons in semiconductors usually behave like a gas―independent particles. However, when confined to two dimensions under a perpendicular magnetic field at low temperatures, they condense into an incompressible quantum liquid. This phenomenon, known as the fractional quantum Hall (FQH) effect1, is a quantum mechanical manifestation of the macroscopic behaviour of correlated electrons that arises when […]