29 research outputs found
A phase transition driven by subtle distortion without broken symmetry on spin, charge and lattice in Layered LnCu4-{\delta}P2(Ln=Eu, Sr)
In the scenario of Landau phase transition theory in condensed matter
physics, any thermal dynamic phase transition must be subject to some kind of
broken symmetries, that are relative to its spin, charge, orbital and lattice.
Here we report a rare phase transition at Tp ~120 K or 140 K in layered
materials LnCu4-{\delta}P2 (Ln=Eu, Sr) driven by a subtle structural-distortion
without any broken symmetry on charge, spin and lattice. The variations of the
lattice parameters, ({\Delta}Lc/Lc) ~ 0.013% or 0.062%, verified by thermal
expansion, is much less than that for a typical crystalline phase transition
(~0.5-1%), but the significant anomaly in heat capacity provides clear evidence
of its intrinsic nature of thermodynamic transition.Comment: 13 pages, 4 figure
Tailoring Dzyaloshinskii-Moriya interaction in a transition metal dichalcogenide by dual-intercalation
Dzyaloshinskii-Moriya interaction (DMI) is vital to form various chiral spin
textures, novel behaviors of magnons and permits their potential applications
in energy-efficient spintronic devices. Here, we realize a sizable bulk DMI in
a transition metal dichalcogenide (TMD) 2H-TaS2 by intercalating Fe atoms,
which form the chiral supercells with broken spatial inversion symmetry and
also act as the source of magnetic orderings. Using a newly developed protonic
gate technology, gate-controlled protons intercalation could further change the
carrier density and intensely tune DMI via the Ruderman-Kittel-Kasuya-Yosida
mechanism. The resultant giant topological Hall resistivity of 1.4 uohm.cm at
-5.2V (about 460% of the zero-bias value) is larger than most of the known
magnetic materials. Theoretical analysis indicates that such a large
topological Hall effect originates from the two-dimensional Bloch-type chiral
spin textures stabilized by DMI, while the large anomalous Hall effect comes
from the gapped Dirac nodal lines by spin-orbit interaction. Dual-intercalation
in 2HTaS2 provides a model system to reveal the nature of DMI in the large
family of TMDs and a promising way of gate tuning of DMI, which further enables
an electrical control of the chiral spin textures and related electromagnetic
phenomena.Comment: 21 pages, 4 figure
Pressure-induced superconductivity in quasi-one-dimensional semimetal
Here we report the discovery of pressure-induced superconductivity in
quasi-one-dimensional , through a combination of
electrical transport, synchrotron x-ray diffraction, and theoretical
calculations. Our transport measurements show that the superconductivity
appears at a critical pressure GPa and is robust
upon further compression up to GPa. The estimated upper critical field
in the pressurized
is much lower than the Pauli limiting field, in contrast to the case in its
isostructural analogs , Ta;
. Concomitant with the occurrence of
superconductivity, anomalies in pressuredependent transport properties are
observed, including sign reversal of Hall coefficient, abnormally enhanced
resistance, and dramatically suppressed magnetoresistance. Meanwhile,
room-temperature synchrotron x-ray diffraction experiments reveal the stability
of the pristine monoclinic structure (space group ) upon compression.
Combined with the density functional theory calculations, we argue that a
pressure-induced Lifshitz transition could be the electronic origin of the
emergent superconductivity in .Comment: 7 pages, 7 figure
Surface skyrmions and dual topological Hall effect in antiferromagnetic topological insulator EuCdAs
In this work, we synthesized single crystal of EuCdAs, which exhibits
A-type antiferromagnetic (AFM) order with in-plane spin orientation below
= 9.5~K.Optical spectroscopy and transport measurements suggest its topological
insulator (TI) nature with an insulating gap around 0.1eV. Remarkably, a dual
topological Hall resistivity that exhibits same magnitude but opposite signs in
the positive to negative and negative to positive magnetic field hysteresis
branches emerges below 20~K. With magnetic force microscopy (MFM) images and
numerical simulations, we attribute the dual topological Hall effect to the
N\'{e}el-type skyrmions stabilized by the interactions between topological
surface states and magnetism, and the sign reversal in different hysteresis
branches indicates potential coexistence of skyrmions and antiskyrmions. Our
work uncovers a unique two-dimensional (2D) magnetism on the surface of
intrinsic AFM TI, providing a promising platform for novel topological quantum
states and AFM spintronic applications.Comment: 7 pages, 3 figure