10 research outputs found
-factor engineering with InAsSb alloys toward zero band gap limit
Band gap is known as an effective parameter for tuning the Lande -factor
in semiconductors and can be manipulated in a wide range through the bowing
effect in ternary alloys. In this work, using the recently developed virtual
substrate technique, high-quality InAsSb alloys throughout the whole Sb
composition range are fabricated and a large -factor of at
the minimum band gap of eV, which is almost twice that in bulk InSb
is found. Further analysis to the zero gap limit reveals a possible gigantic
-factor of with a peculiar relativistic Zeeman effect that
disperses as the square root of magnetic field. Such a -factor enhancement
toward the narrow gap limit cannot be quantitatively described by the
conventional Roth formula, as the orbital interaction effect between the nearly
triply degenerated bands becomes the dominant source for the Zeeman splitting.
These results may provide new insights into realizing large -factors and
spin polarized states in semiconductors and topological materials
Giant -factors and fully spin-polarized states in metamorphic short-period InAsSb/InSb superlattices
Realizing a large Land\'{e} -factor of electrons in solid-state materials
has long been thought of as a rewarding task as it can trigger abundant
immediate applications in spintronics and quantum computing. Here, by using
metamorphic InAsSb/InSb superlattices (SLs), we demonstrate an unprecedented
high value of , twice larger than that in bulk InSb, and fully
spin-polarized states at low magnetic fields. In addition, we show that the
-factor can be tuned on demand from 20 to 110 via varying the SL period. The
key ingredients of such a wide tunability are the wavefunction mixing and
overlap between the electron and hole states, which have drawn little attention
in prior studies. Our work not only establishes metamorphic InAsSb/InSb as a
promising and competitive material platform for future quantum devices but also
provides a new route toward -factor engineering in semiconductor structures
Weyl Fermion magneto-electrodynamics and ultralow field quantum limit in TaAs
Topological semimetals are predicted to exhibit unconventional electrodynamics, but a central experimental challenge is singling out the contributions from the topological bands. TaAs is the prototypical example, where 24 Weyl points and 8 trivial Fermi surfaces make the interpretation of any experiment in terms of band topology ambiguous. We report magneto-infrared reflection spectroscopy measurements on TaAs. We observed sharp inter-Landau level transitions from a single pocket of Weyl Fermions in magnetic fields as low as 0.4 tesla. We determine the W2 Weyl point to be 8.3 meV below the Fermi energy, corresponding to a quantum limit—the field required to reach the lowest LL—of 0.8 tesla—unprecedentedly low for Weyl Fermions. LL spectroscopy allows us to isolate these Weyl Fermions from all other carriers in TaAs, and our result provides a way for directly exploring the more exotic quantum phenomena in Weyl semimetals, such as the chiral anomaly
Electronic correlations in nodal-line semimetals
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Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
Optical transitions between Landau levels (LL) in solids are described by selection rules associated with the LL index. Here, the authors perform photocurrent spectroscopy measurements on high-quality bilayer graphene to investigate the interband LL transitions, and observe valley-dependent optical transitions obeying unusual selection rules
Author Correction: Unconventional valley-dependent optical selection rules and landau level mixing in bilayer graphene
An amendment to this paper has been published and can be accessed via a link at the top of the paper
Engineering Dirac Materials: Metamorphic InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> Superlattices with Ultralow Bandgap
Quasiparticles
with Dirac-type dispersion can be observed in nearly
gapless bulk semiconductors alloys in which the bandgap is controlled
through the material composition. We demonstrate that the Dirac dispersion
can be realized in short-period InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> metamorphic superlattices with
the bandgap tuned to zero by adjusting the superlattice period and
layer strain. The new material has anisotropic carrier dispersion:
the carrier energy associated with the in-plane motion is proportional
to the wave vector and characterized by the Fermi velocity <i>v</i><sub>F</sub>, and the dispersion corresponding to the motion
in the growth direction is quadratic. Experimental estimate of the
Fermi velocity gives <i>v</i><sub>F</sub> = 6.7 × 10<sup>5</sup> m/s. Remarkably, the Fermi velocity in this system can be
controlled by varying the overlap between electron and hole states
in the superlattice. Extreme design flexibility makes the short-period
metamorphic InAs<sub>1–<i>x</i></sub>Sb<sub><i>x</i></sub>/InAs<sub>1–<i>y</i></sub>Sb<sub><i>y</i></sub> superlattice a new prospective platform
for studying the effects of charge-carrier chirality and topologically
nontrivial states in structures with the inverted bandgaps