Optoelectronic transport through quantum Hall edge states

Abstract

We use GaAs-based quantum point contacts as mesoscopic detectors to locally analyze the flow of photogenerated electrons in a two-dimensional electron gas (2DEG) at perpendicular, quantizing magnetic fields. The 2DEG is formed within a quantum well of a doped GaAs/AlGaAs-heterostructure. We find an optoelectronic signal along the lateral boundaries of the 2DEG, which is consistent with an optically induced quantum transport through quantum Hall edge channels. We demonstrate that photogenerated electrons can be directly injected into an edge channel, transported across several tens of micrometers and read-out on-chip by the quantum point contact.

Ultrafast and Local Optoelectronic Transport in Topological Insulators

“…[ 64 ] The long‐range detection stands in stark contrast to the Landauer–Büttiker description of quantized conductance and previous mesoscopic optoelectronic detection schemes, which require a coherent transport between the current and voltage probes. [ 65–67 ] The observed conductance of e 2 / h suggests spin‐polarized transport, which is consistent with the helical dispersion of the topological surface states. For excitation near the sample edge, a net photocurrent is locally generated if the propagation of charge carriers toward the sample edge is effectively cut off, possibly by localized scattering sources.…”

The Anomalous Photo‐Nernst Effect of Massive Dirac Fermions In HfTe5

“…[ 35 ] In such a scenario, the photocurrent amplitude would be expected to oscillate as the external magnetic field drives transitions through the 2D Landau levels. [ 36 ] Rather, photocurrent line scans (along the dotted line in Figure 2b) reveal a step‐like, quickly saturating behaviour up to the highest magnetic fields of our experiments (Figure 2c).…”

Observation of chiral photocurrent transport in the quantum Hall regime in graphene

“…Our photocurrent measurement provides deeper insights into the carrier transport behavior in the quantum Hall regime, in particular, their chirality above and below the Dirac point. Such optical probing permits the study of the quantum Hall states in an intermediate length-scale regime, which could be applied to other 2D material systems [31][32][33][34]. In addition, this work will contribute to developing novel ap-plications of semiconductor materials, such as engineering the Peltier coefficient [35].…”