Nanowerk April 15, 2024 Metrological applications of the quantum anomalous Hall effect are currently restricted by the need for low measurement currents and low temperatures. Researchers in Germany developed a measurement scheme that increases the robustness of a zero-magnetic-field quantum anomalous Hall resistor and extends its operating range to higher currents. In the scheme, they simultaneously injected current into two disconnected perimeters of a multi-terminal Corbino device to balance the electrochemical potential between the edges. This screened the electric field that drove backscattering through the bulk and thus improved the stability of the quantization at increased currents. According to the […]
Tag Archives: Quantum Hall effect
Electrons become fractions of themselves in graphene
Science Daily February 21, 2024 The fractional quantum anomalous Hall effect (FQAHE), the analogue of the fractional quantum Hall effect at zero magnetic field, is predicted to exist in topological flat bands under spontaneous time-reversal-symmetry breaking. The demonstration of FQAHE could lead to non-Abelian anyons that form the basis of topological quantum computation. So far, FQAHE has been observed only in twisted MoTe2 at a moiré filling factor v > 1/2. Graphene-based moiré superlattices are believed to host FQAHE with the potential advantage of superior material quality and higher electron mobility. At zero magnetic field, an international team of researchers (USA – […]
Communing with nothingness
Nanowerk November 6, 2023 Light–matter interaction in the ultrastrong coupling regime is attracting considerable attention owing to its applications to coherent control of material properties by a vacuum fluctuation field. However, electrical access to such an ultra-strongly coupled system is very challenging. Researchers in Japan have fabricated a gate-defined quantum point contact (QPC) near the gap of a terahertz (THz) split-ring resonator (SRR) fabricated on a GaAs two-dimensional (2D) electron system. By illuminating the system with external THz radiation, the QPC showed a photocurrent spectrum which exhibited significant anticrossing that came from coupling between the cyclotron resonance of the 2D […]
Vacuum fluctuations break topological protection
Phys.org March 4, 2022 The prospect of controlling the electronic properties of materials via the vacuum fields of cavity electromagnetic resonators is emerging as one of the frontiers of condensed matter physics. An international team of researchers (Switzerland, France) found that the enhancement of vacuum field fluctuations in subwavelength split-ring resonators strongly affects the quantum Hall electron transport in high-mobility two-dimensional electron gases. The observed breakdown of the topological protection of the integer quantum Hall effect is interpreted in terms of a long-range cavity-mediated electron hopping where the anti-resonant terms of the light-matter coupling develop into a finite resistivity induced […]