Abstract
As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm’s law. Depending on the length scales of momentum conserving (
l
MC
) and ...relaxing (
l
MR
) electron scattering, and the device size (
d
), current flows may shift from ohmic to ballistic to hydrodynamic regimes. So far, an in situ methodology to obtain these parameters within a micro/nanodevice is critically lacking. In this context, we exploit Sondheimer oscillations, semi-classical magnetoresistance oscillations due to helical electronic motion, as a method to obtain
l
MR
even when
l
MR
≫
d
. We extract
l
MR
from the Sondheimer amplitude in WP
2
, at temperatures up to
T
~ 40 K, a range most relevant for hydrodynamic transport phenomena. Our data on
μ
m-sized devices are in excellent agreement with experimental reports of the bulk
l
MR
and confirm that WP
2
can be microfabricated without degradation. These results conclusively establish Sondheimer oscillations as a quantitative probe of
l
MR
in micro-devices.
Weyl semimetals, characterized by nodal points in the bulk and Fermi arc states on the surface, have recently attracted extensive attention due to their potential application as materials for ...low‐energy‐consumption electronics. The thermodynamic and transport properties of a theoretically predicted Weyl semimetal NbIrTe4 is measured in high magnetic fields up to 35 T and low temperatures down to 0.4 K. Remarkably, NbIrTe4 exhibits a nonsaturating transverse magnetoresistance that follows a power‐law dependence in B. Low‐field Hall measurements reveal that hole‐like carriers dominate the transport for T > 80 K, while the significant enhancement of electron mobilities obtained by lowering T results in a non‐negligible contribution from electron‐like carriers, which is responsible for the observed nonlinear Hall resistivity at low T. The Shubnikov‐de Haas oscillations of the Hall resistivity under high B give the light effective masses of charge carriers and the nontrivial Berry phase associated with Weyl fermions. Further first‐principles calculations confirm the existence of 16 Weyl points located at kz
= 0, ± 0.02, and ± 0.2 planes in the Brillouin zone.
The unique band topology of Dirac/Weyl semimetals can often lead to interesting charge‐carrier‐transport phenomena. A large nonsaturating power‐law magnetoresistance is observed in NbIrTe4. Detailed low‐temperature Hall effect and quantum oscillation measurements point to coexistence of conventional charge carriers and “relativistic” carriers, which is consistent with the band structure calculation results, revealing 16 Weyl points.
The motivation to search for signatures of superconductivity in Weyl semi-metals and other topological phases lies in their potential for hosting exotic phenomena such as nonzero-momentum pairing or ...the Majorana fermion, a viable candidate for the ultimate realization of a scalable quantum computer. Until now, however, all known reports of superconductivity in type-I Weyl semi-metals have arisen through surface contact with a sharp tip, focused ion-beam surface treatment or the application of high pressures. Here, we demonstrate the observation of superconductivity in single crystals, even an as-grown crystal, of the Weyl semi-metal tantalum phosphide (TaP), at ambient pressure. A superconducting transition temperature, T c , varying between 1.7 and 5.3 K, is observed in different samples, both as-grown and microscopic samples processed with focused ion beam (FIB) etching. Our data show that the superconductivity present in the as-grown crystal is inhomogeneous yet three-dimensional. For samples fabricated with FIB, we observe, in addition to the three-dimensional superconductivity, a second superconducting phase that resides on the sample surface. Through measurements of the characteristic fields as a function of temperature and angle, we are able to confirm the dimensionality of the two distinct superconducting phases.
Abstract The kagome metals AV 3 Sb 5 (A = K, Rb, Cs) present an ideal sandbox to study the interrelation between multiple coexisting correlated phases such as charge order and superconductivity. So ...far, no consensus on the microscopic nature of these states has been reached as the proposals struggle to explain all their exotic physical properties. Among these, field-switchable electric magneto-chiral anisotropy (eMChA) in CsV 3 Sb 5 provides intriguing evidence for a rewindable electronic chirality, yet the other family members have not been likewise investigated. Here, we present a comparative study of magneto-chiral transport between CsV 3 Sb 5 and KV 3 Sb 5 . Despite their similar electronic structure, KV 3 Sb 5 displays negligible eMChA, if any, and with no field switchability. This is in stark contrast to the non-saturating eMChA in CsV 3 Sb 5 even in high fields up to 35 T. In light of their similar band structures, the stark difference in eMChA suggests its origin in the correlated states. Clearly, the V kagome nets alone are not sufficient to describe the physics and the interactions with their environment are crucial in determining the nature of their low-temperature state.
As conductors in electronic applications shrink, microscopic conduction processes lead to strong deviations from Ohm's law. Depending on the length scales of momentum conserving (l
) and relaxing (l
...) electron scattering, and the device size (d), current flows may shift from ohmic to ballistic to hydrodynamic regimes. So far, an in situ methodology to obtain these parameters within a micro/nanodevice is critically lacking. In this context, we exploit Sondheimer oscillations, semi-classical magnetoresistance oscillations due to helical electronic motion, as a method to obtain l
even when l
≫ d. We extract l
from the Sondheimer amplitude in WP
, at temperatures up to T ~ 40 K, a range most relevant for hydrodynamic transport phenomena. Our data on μm-sized devices are in excellent agreement with experimental reports of the bulk l
and confirm that WP
can be microfabricated without degradation. These results conclusively establish Sondheimer oscillations as a quantitative probe of l
in micro-devices.
Abstract
Weyl semimetals, characterized by nodal points in the bulk and Fermi arc states on the surface, have recently attracted extensive attention due to their potential application as materials ...for low‐energy‐consumption electronics. The thermodynamic and transport properties of a theoretically predicted Weyl semimetal NbIrTe
4
is measured in high magnetic fields up to 35 T and low temperatures down to 0.4 K. Remarkably, NbIrTe
4
exhibits a nonsaturating transverse magnetoresistance that follows a power‐law dependence in
B
. Low‐field Hall measurements reveal that hole‐like carriers dominate the transport for
T >
80 K, while the significant enhancement of electron mobilities obtained by lowering
T
results in a non‐negligible contribution from electron‐like carriers, which is responsible for the observed nonlinear Hall resistivity at low
T
. The Shubnikov‐de Haas oscillations of the Hall resistivity under high
B
give the light effective masses of charge carriers and the nontrivial Berry phase associated with Weyl fermions. Further first‐principles calculations confirm the existence of 16 Weyl points located at
k
z
= 0, ± 0.02, and ± 0.2 planes in the Brillouin zone.
npj Quantum Materials, 9, 20 (2024) The kagome metals AV$_3$Sb$_5$ (A=K,Rb,Cs) present an ideal sandbox to study
the interrelation between multiple coexisting correlated phases such as charge
order ...and superconductivity. So far, no consensus on the microscopic nature of
these states has been reached as the proposals struggle to explain all their
exotic physical properties. Among these, field-switchable electric
magneto-chiral anisotropy (eMChA) in CsV$_3$Sb$_5$ provides intriguing evidence
for a rewindable electronic chirality, yet the other family members have not
been likewise investigated. Here, we present a comparative study of
magneto-chiral transport between CsV$_3$Sb$_5$ and KV$_3$Sb$_5$. Despite their
similar electronic structure, KV$_3$Sb$_5$ displays negligible eMChA, if any,
and with no field switchability. This is in stark contrast to the
non-saturating eMChA in CsV$_3$Sb$_5$ even in high fields up to 35 T. In light
of their similar band structures, the stark difference in eMChA suggests its
origin in the correlated states. Clearly, the V kagome nets alone are not
sufficient to describe the physics and the interactions with their environment
are crucial in determining the nature of their low-temperature state.
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