28 research outputs found
Singular robust room-temperature spin response from topological Dirac fermions
Topological insulators are a class of solids in which the nontrivial inverted
bulk band structure gives rise to metallic surface states that are robust
against impurity scattering. In three-dimensional (3D) topological insulators,
however, the surface Dirac fermions intermix with the conducting bulk, thereby
complicating access to the low energy (Dirac point) charge transport or
magnetic response. Here we use differential magnetometry to probe spin rotation
in the 3D topological material family (BiSe, BiTe, and
SbTe). We report a paramagnetic singularity in the magnetic
susceptibility at low magnetic fields which persists up to room temperature,
and which we demonstrate to arise from the surfaces of the samples. The
singularity is universal to the entire family, largely independent of the bulk
carrier density, and consistent with the existence of electronic states near
the spin-degenerate Dirac point of the 2D helical metal. The exceptional
thermal stability of the signal points to an intrinsic surface cooling process,
likely of thermoelectric origin, and establishes a sustainable platform for the
singular field-tunable Dirac spin response.Comment: 20 pages, 14 figure
ΠΠΎΠ²ΡΡΠ΅Π½ΠΈΠ΅ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΠΈ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²ΡΠΈΠΊΠΎΠ² Π±ΠΎΡΡΠΎΠ²ΠΎΠΉ ΡΠ°Π΄ΠΈΠΎΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΉ Π°ΠΏΠΏΠ°ΡΠ°ΡΡΡΡ ΠΊΠΎΡΠΌΠΈΡΠ΅ΡΠΊΠΈΡ Π°ΠΏΠΏΠ°ΡΠ°ΡΠΎΠ² Π½Π° Π±Π°Π·Π΅ ΠΈΠ½ΡΠ΅Π³ΡΠ°ΡΠΈΠΈ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠΎΠ½Π½ΡΡ ΡΠΈΡΡΠ΅ΠΌ
ΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄ ΡΠ΅Π°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΈΠ½ΡΠΎΡΠΌΠ°ΡΠΈΠΎΠ½Π½ΠΎΠ³ΠΎ Π²Π·Π°ΠΈΠΌΠΎΠ΄Π΅ΠΉΡΡΠ²ΠΈΡ ΠΏΡΠΎΠ΅ΠΊΡΠΈΡΠΎΠ²ΡΠΈΠΊΠΎΠ² Π±ΠΎΡΡΠΎΠ²ΠΎΠΉ ΡΠ°Π΄ΠΈΠΎΡΠ»Π΅ΠΊΡΡΠΎΠ½Π½ΠΎΠΉ Π°ΠΏΠΏΠ°ΡΠ°ΡΡΡΡ, ΠΏΠΎΠ²ΡΡΠ°ΡΡΠΈΠΉ ΡΡΡΠ΅ΠΊΡΠΈΠ²Π½ΠΎΡΡΡ ΠΈΡΠΏΠΎΠ»ΡΠ·ΠΎΠ²Π°Π½ΠΈΡ ΡΠ΅ΡΡΡΡΠΎΠ² ΠΈ ΡΠΏΡΠ°Π²Π»Π΅Π½ΠΈΠ΅ ΠΏΡΠΎΠΈΠ·Π²ΠΎΠ΄ΡΡΠ²Π΅Π½Π½ΡΠΌΠΈ ΠΏΡΠΎΡΠ΅ΡΡΠ°ΠΌΠΈ. ΠΡΠ΅Π΄ΡΡΠ°Π²Π»Π΅Π½Π° ΠΊΠΎΠ½ΡΠ΅ΠΏΡΠΈΡ ΠΏΡΠ°ΠΊΡΠΈΡΠ΅ΡΠΊΠΎΠΉ ΡΠ΅Π°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΏΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Π½ΠΎΠ³ΠΎ ΠΏΠΎΠ΄Ρ
ΠΎΠ΄Π° Π² ΡΡΠ΅Π΄Π΅ PLM-ΡΠΈΡΡΠ΅ΠΌΡ Enovia SmarTeam. Π Π°Π·ΡΠ°Π±ΠΎΡΠ°Π½ Π°Π»Π³ΠΎΡΠΈΡΠΌ ΡΠΎΡ
ΡΠ°Π½Π΅Π½ΠΈΡ Π΄Π°Π½Π½ΡΡ
ΠΏΡΠΎΠ΅ΠΊΡΠΎΠ² EDA-ΡΠΈΡΡΠ΅ΠΌΡ Altium Designer Π² Ρ
ΡΠ°Π½ΠΈΠ»ΠΈΡΠ΅ Π΄Π°Π½Π½ΡΡ
PLM-ΡΠΈΡΡΠ΅ΠΌΡ Enovia SmarTeam. Π‘ΡΠΎΡΠΌΠΈΡΠΎΠ²Π°Π½ ΠΌΠ΅Ρ
Π°Π½ΠΈΠ·ΠΌ Π³Π΅Π½Π΅ΡΠ°ΡΠΈΠΈ ΠΊΠΎΠ½ΡΡΡΡΠΊΡΠΎΡΡΠΊΠΈΡ
Π΄ΠΎΠΊΡΠΌΠ΅Π½ΡΠΎΠ² Π½Π° Π±Π°Π·Π΅ ΡΠΎΡΠΌΠ°ΡΠ° Ρ
ΡΠ°Π½Π΅Π½ΠΈΡ Π΄Π°Π½Π½ΡΡ
JSON
Stable topological insulators achieved using high energy electron beams
Topological insulators are transformative quantum solids with
immune-to-disorder metallic surface states having Dirac band structure.
Ubiquitous charged bulk defects, however, pull the Fermi energy into the bulk
bands, denying access to surface charge transport. Here we demonstrate that
irradiation with swift ( MeV energy) electron beams allows to
compensate these defects, bring the Fermi level back into the bulk gap, and
reach the charge neutrality point (CNP). Controlling the beam fluence we tune
bulk conductivity from \textit{p}- (hole-like) to \textit{n}-type
(electron-like), crossing the Dirac point and back, while preserving the Dirac
energy dispersion. The CNP conductance has a two-dimensional (2D) character on
the order of ten conductance quanta , and reveals, both in
BiTe and BiSe, the presence of only two quantum channels
corresponding to two topological surfaces. The intrinsic quantum transport of
the topological states is accessible disregarding the bulk size.Comment: Main manuscript - 12 pages, 4 figures; Supplementary file - 15 pages,
11 figures, 1 Table, 4 Note
Tunable magnetic domains in ferrimagnetic MnSbTe
Highly tunable properties make Mn(Bi,Sb)Te a rich playground for
exploring the interplay between band topology and magnetism: On one end,
MnBiTe is an antiferromagnetic topological insulator, while the
magnetic structure of MnSbTe (MST) can be tuned between
antiferromagnetic and ferrimagnetic. Motivated to control electronic properties
through real-space magnetic textures, we use magnetic force microscopy (MFM) to
image the domains of ferrimagnetic MST. We find that magnetic field tunes
between stripe and bubble domain morphologies, raising the possibility of
topological spin textures. Moreover, we combine in situ transport with domain
manipulation and imaging to both write MST device properties and directly
measure the scaling of the Hall response with domain area. This work
demonstrates measurement of the local anomalous Hall response using MFM, and
opens the door to reconfigurable domain-based devices in the M(B,S)T family
Hydrogen induces chiral conduction channels in the topological magnet
Chirality, a characteristic handedness that distinguishes 'left' from
'right', cuts widely across all of nature, from the structure of DNA to
opposite chirality of particles and antiparticles. In condensed matter
chiral fermions have been identified in Weyl semimetals through their
unconventional electrodynamics arising from 'axial' charge imbalance between
chiral Weyl nodes of topologically nontrivial electronic bands. Up to now it
has been challenging or impossible to create transport channels of Weyl
fermions in a single material that could be easily configured for advancing
chiral logic or spintronics. Here we generate chirality-directed
conduction channels in inversion-symmetric Weyl ferromagnet (FM) ,
emergent from a deep connection between chirality in reciprocal and real space.
We alter the bandstructure on-demand with an intake and a subsequent release of
ionic hydrogen () a process we show to induce the tilt and rotation of
Weyl bands. The transformed Weyl FM states feature a doubled Curie temperature
and an enhanced angular transport chirality synchronous with a rare
field-antisymmetric longitudinal resistance a low-field tunable 'chiral
switch' that roots in the interplay of Berry curvature, chiral anomaly
and hydrogen-engendered mutation of Weyl nodes
Structural and magnetic properties of molecular beam epitaxy (MnSb2Te4)x(Sb2Te3)1-x topological materials with exceedingly high Curie temperature
Tuning magnetic properties of magnetic topological materials is of interest
to realize elusive physical phenomena such as quantum anomalous hall effect
(QAHE) at higher temperatures and design topological spintronic devices.
However, current topological materials exhibit Curie temperature (TC) values
far below room temperature. In recent years, significant progress has been made
to control and optimize TC, particularly through defect engineering of these
structures. Most recently we showed evidence of TC values up to 80K for
(MnSb2Te4)x(Sb2Te3)1-x, where x is greater than or equal to 0.7 and less than
or equal to 0.85, by controlling the compositions and Mn content in these
structures. Here we show further enhancement of the TC, as high as 100K, by
maintaining high Mn content and reducing the growth rate from 0.9 nm/min to 0.5
nm/min. Derivative curves reveal the presence of two TC components contributing
to the overall value and propose TC1 and TC2 have distinct origins: excess Mn
in SLs and Mn in Sb2-yMnyTe3QLs alloys, respectively. In pursuit of elucidating
the mechanisms promoting higher Curie temperature values in this system, we
show evidence of structural disorder where Mn is occupying not only Sb sites
but also Te sites, providing evidence of significant excess Mn and a new
crystal structure:(Mn1+ySb2-yTe4)x(Sb2-yMnyTe3)1-x. Our work shows progress in
understanding how to control magnetic defects to enhance desired magnetic
properties and the mechanism promoting these high TC in magnetic topological
materials such as (Mn1+ySb2-yTe4)x(Sb2-yMnyTe3)1-x