10 research outputs found
Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.
In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe2). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe2 thin films with a high precision rotation stage, we map the upper critical field Hc2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field Hc2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of Hc2 in Ising superconductors
Hysteretic Magnetotransport in SmB6 at Low Magnetic Fields
Utilizing Corbino disc structures, we have examined the magnetic field
response of resistivity for the surface states of SmB6 on different crystalline
surfaces at low temperatures. Our results reveal a hysteretic behavior whose
magnitude depends on the magnetic field sweep rate and temperature. Although
this feature becomes smaller when the field sweep is slower, a complete
elimination or saturation is not observed in our slowest sweep-rate
measurements, which is much slower than a typical magnetotransport trace. These
observations cannot be explained by quantum interference corrections such as
weak anti-localization. Instead, they are consistent with behaviors of glassy
surface magnetic ordering, whose magnetic origin is most likely from samarium
oxide (Sm2O3) forming on the surface during exposure to ambient conditions
Emergent superconducting fluctuations in a compressed kagome superconductor
The recent discovery of superconductivity (SC) and charge density wave (CDW)
in kagome metals AV3Sb5 (A = K, Rb, Cs) provides an ideal playground for the
study of emergent electronic orders. Application of moderate pressure leads to
a two-dome-shaped SC phase regime in CsV3Sb5 accompanied by the destabilizing
of CDW phase; such unconventional evolution of SC may involve the
pressure-induced formation of a new stripe-like CDW order resembling that in
La-214 cuprate superconductors. Nonetheless, the nature of this pressure-tuned
SC state and its interplay with the stripe order are yet to be explored. Here,
we perform soft point-contact spectroscopy (SPCS) measurements in CsV3Sb5 to
investigate the evolution of superconducting order parameter with pressure.
Surprisingly, we find that the superconducting gap is significantly enhanced
between the two SC domes, at which the zero-resistance temperature is
suppressed and the transition is remarkably broadened. Moreover, the
temperature dependence of the SC gap in this pressure range severely deviates
from the conventional BCS behavior, evidencing for strong Cooper pair phase
fluctuations. These findings reveal the complex intertwining of the stripe-like
CDW with SC in the compressed CsV3Sb5, suggesting striking parallel to the
cuprate superconductor La2-xBaxCuO4. Our results point to the essential role of
charge degree of freedom in the development of intertwining electronic orders,
thus provides new constraints for theories.Comment: 16 pages, 4 figure
Spin-orbit-coupled triangular-lattice spin liquid in rare-earth chalcogenides
Spin-orbit coupling is an important ingredient in many spin liquid candidate
materials, especially among the rare-earth magnets and Kitaev materials. We
explore the rare-earth chalcogenides NaYbS where the Yb ions form a
perfect triangular lattice. Unlike its isostructural counterpart YbMgGaO
and the kagom\'{e} lattice herbertsmithite, this material does not have any
site disorders both in magnetic and non-magnetic sites. We carried out the
thermodynamic and inelastic neutron scattering measurements. The magnetic
dynamics could be observed with a broad gapless excitation band up to 1.0 meV
at 50 mK and 0 T, no static long-range magnetic ordering is detected down to 50
mK. We discuss the possibility of Dirac spin liquid for NaYbS. We identify
the experimental signatures of field-induced transitions from the disordered
spin liquid to an ordered antiferromagnet with an excitation gap at finite
magnetic fields and discuss this result with our Monte Carlo calculation of the
proposed spin model. Our findings could inspire further interests in the
spin-orbit-coupled spin liquids and the magnetic ordering transition from them
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Magnetic Field Enhanced Superconductivity in Epitaxial Thin Film WTe2.
In conventional superconductors an external magnetic field generally suppresses superconductivity. This results from a simple thermodynamic competition of the superconducting and magnetic free energies. In this study, we report the unconventional features in the superconducting epitaxial thin film tungsten telluride (WTe2). Measuring the electrical transport properties of Molecular Beam Epitaxy (MBE) grown WTe2 thin films with a high precision rotation stage, we map the upper critical field Hc2 at different temperatures T. We observe the superconducting transition temperature T c is enhanced by in-plane magnetic fields. The upper critical field Hc2 is observed to establish an unconventional non-monotonic dependence on temperature. We suggest that this unconventional feature is due to the lifting of inversion symmetry, which leads to the enhancement of Hc2 in Ising superconductors
A new class of bilayer kagome lattice compounds with Dirac nodal lines and pressure-induced superconductivity
Kagome lattice composed of transition-metal ions provides a great opportunity
to explore the intertwining between geometry, electronic orders and band
topology. The discovery of multiple competing orders that connect intimately
with the underlying topological band structure in nonmagnetic kagome metals
VSb ( = K, Rb, Cs) further pushes this topic to the quantum
frontier. Here we report the discovery and characterization of a new class of
vanadium-based compounds with kagome bilayers, namely VSb ( = K,
Rb, Cs) and VSb, which, together with VSb, compose a series
of kagome compounds with a generic chemical formula
(Sb)(VSb) (m = 1, 2; n = 1, 2). Theoretical
calculations combined with angle-resolved photoemission measurements reveal
that these compounds feature Dirac nodal lines in close vicinity to the Fermi
level. Pressure-induced superconductivity in VSb further suggests
promising emergent phenomena in these materials. The establishment of a new
family of layered kagome materials paves the way for designer of fascinating
kagome systems with diverse topological nontrivialities and collective ground
states.Comment: 16 pages, 4 figure
Two-dimensional phase diagram of the charge density wave in doped CsV3Sb5
Abstract Kagome superconductors AV3Sb5 (A = K, Rb and Cs) have attracted much recent attention due to the coexistence of multiple exotic orders. Among them, the charge density wave (CDW) order has been shown to host various unconventional behaviors. Here, we investigate the CDW order by a combination of both bulk and surface doping methods. While element substitutions in bulk doping change both carriers and the crystal lattice, the surface doping primarily tunes the carrier concentration. As such, our results reveal a two-dimensional phase diagram of the CDW in doped CsV3Sb5. In the lightly bulk doped regime, the existence of CDW order is reversible by tuning the carrier concentration. But excessive bulk doping permanently destroys the CDW, regardless of the carrier doping level. These results provide insights to the origin of the CDW from both electronic and structural degrees of freedom. They also open an avenue for manipulating the exotic CDW order in Kagome superconductors