57 research outputs found
Zero-Energy Modes from Coalescing Andreev States in a Two-Dimensional Semiconductor-Superconductor Hybrid Platform
We investigate zero-bias conductance peaks that arise from coalescing subgap
Andreev states, consistent with emerging Majorana zero modes, in hybrid
semiconductor-superconductor wires defined in a two-dimensional InAs/Al
heterostructure using top-down lithography and gating. The measurements
indicate a hard superconducting gap, ballistic tunneling contact, and in-plane
critical fields up to ~T. Top-down lithography allows complex geometries,
branched structures, and straightforward scaling to multicomponent devices
compared to structures made from assembled nanowires.Comment: Includes Supplementary Materia
Dynamic detection of electron spin accumulation in ferromagnet-semiconductor devices by ferromagnetic resonance
A distinguishing feature of spin accumulation in ferromagnet-semiconductor
devices is precession of the non-equilibrium spin population of the
semiconductor in a magnetic field. This is the basis for detection techniques
such as the Hanle effect, but these approaches become less effective as the
spin lifetime in the semiconductor decreases. For this reason, no electrical
Hanle measurement has been demonstrated in GaAs at room temperature. We show
here that by forcing the magnetization in the ferromagnet (the spin injector
and detector) to precess at the ferromagnetic resonance frequency, an
electrically generated spin accumulation can be detected from 30 to 300 K. At
low temperatures, the distinct Larmor precession of the spin accumulation in
the semiconductor can be detected by ferromagnetic resonance in an oblique
field. We verify the effectiveness of this new spin detection technique by
comparing the injection bias and temperature dependence of the measured spin
signal to the results obtained using traditional methods. We further show that
this new approach enables a measurement of short spin lifetimes (< 100 psec), a
regime that is not accessible in semiconductors using traditional Hanle
techniques.Comment: 4 figure
Local Density of States and Interface Effects in Semimetallic ErAs Nanoparticles Embedded in GaAs
The atomic and electronic structures of ErAs nanoparticles embedded within a
GaAs matrix are examined via cross-sectional scanning tunneling microscopy and
spectroscopy (XSTM/XSTS). The local density of states (LDOS) exhibits a finite
minimum at the Fermi level demonstrating that the nanoparticles remain
semimetallic despite the predictions of previous models of quantum confinement
in ErAs. We also use XSTS to measure changes in the LDOS across the ErAs/GaAs
interface and propose that the interface atomic structure results in electronic
states that prevent the opening of a band gap.Comment: 9 pages, 3 figur
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