48 research outputs found
Observation of spin-orbit coupling induced Weyl points and topologically protected Kondo effect in a two-electron double quantum dot
Recent years have brought an explosion of activities in the research of
topological aspects of condensed-matter systems. Topologically non-trivial
phases of matter are typically accompanied by protected surface states or
exotic degenerate excitations such as Majorana end states or Haldane's
localized spinons. Topologically protected degeneracies can, however, also
appear in the bulk. An intriguing example is provided by Weyl semimetals, where
topologically protected electronic band degeneracies and exotic surface states
emerge even in the absence of interactions. Here we demonstrate experimentally
and theoretically that Weyl degeneracies appear naturally in an interacting
quantum dot system, for specific values of the external magnetic field. These
magnetic Weyl points are robust against spin-orbit coupling unavoidably present
in most quantum dot devices. Our transport experiments through an InAs double
dot device placed in magnetic field reveal the presence of a pair of Weyl
points, exhibiting a robust ground state degeneracy and a corresponding
protected Kondo effect.Comment: 6 pages, 3 figures. Supplementary Information can be downloaded as an
ancillary pdf fil
Processing sweet sorghum into bioethanol - an integrated approach
Numerous evidences have been provided that juice of sweet sorghum and the leftover after squeezing, the bagasse can be a proper feedstock for bioethanol production. The possibility to integrate a side stream of sweet sorghum processing into the biomass-to-ethanol process was investigated in this study. The liquid fraction, a side stream of the necessary pretreatment of the bagasse was utilized as carbon source for Trichoderma reesei RUT-C30 to produce cellulase enzymes for biomass conversion. However, to overcome the inhibitory nature of the liquid fraction, pre-adaptation of the fungus on solid media was carried out previous to submerged fermentations. The results show that with this approach the lag phase caused by the inhibitors could be markedly shortened and an enhancement of the final enzyme production could be achieved when comparing the pre-adapted strains to reference
A kakasmandikó (Erythronium dens-canis L.) demográfiai kutatásának módszertani megalapozása
Point contacts in encapsulated graphene
We present a novel method to establish inner point contacts on hexagonal
boron nitride (hBN) encapsulated graphene heterostructures with dimensions as
small as 100 nm by pre-patterning the top-hBN in a separate step prior to
dry-stacking. 2 and 4-terminal field effect measurements between different lead
combinations are in qualitative agreement with an electrostatic model assuming
pointlike contacts. The measured contact resistances are 0.5-1.5 k per
contact, which is quite low for such small contacts. By applying a
perpendicular magnetic fields, an insulating behaviour in the quantum Hall
regime was observed, as expected for inner contacts. The fabricated contacts
are compatible with high mobility graphene structures and open up the field for
the realization of several electron optical proposals
Exfoliation of single layer BiTeI flakes
Spin orbit interaction can be strongly boosted when a heavy element is
embedded into an inversion asymmetric crystal field. A simple structure to
realize this concept in a 2D crystal contains three atomic layers, a middle one
built up from heavy elements generating strong atomic spin-orbit interaction
and two neighboring atomic layers with different electron negativity. BiTeI is
a promising candidate for such a 2D crystal, since it contains heavy Bi layer
between Te and I layers. Recently the bulk form of BiTeI attracted considerable
attention due to its giant Rashba interaction, however, 2D form of this crystal
was not yet created. In this work we report the first exfoliation of single
layer BiTeI using a recently developed exfoliation technique on stripped gold.
Our combined scanning probe studies and first principles calculations show that
SL BiTeI flakes with sizes of 100 m were achieved which are stable at
ambient conditions. The giant Rashba splitting and spin-momentum locking of
this new member of 2D crystals open the way towards novel spintronic
applications and synthetic topological heterostructures.Comment: 20 pages, 5 figure
Boosting proximity spin orbit coupling in graphene/WSe heterostructures via hydrostatic pressure
Van der Waals heterostructures composed of multiple few layer crystals allow
the engineering of novel materials with predefined properties. As an example,
coupling graphene weakly to materials with large spin orbit coupling (SOC)
allows to engineer a sizeable SOC in graphene via proximity effects. The
strength of the proximity effect depends on the overlap of the atomic orbitals,
therefore, changing the interlayer distance via hydrostatic pressure can be
utilized to enhance the interlayer coupling between the layers. In this work,
we report measurements on a graphene/WSe heterostructure exposed to
increasing hydrostatic pressure. A clear transition from weak localization to
weak anti-localization is visible as the pressure increases, demonstrating the
increase of induced SOC in graphene