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 […]