107 research outputs found
Detection of electronic nematicity using scanning tunneling microscopy
Electronic nematic phases have been proposed to occur in various correlated
electron systems and were recently claimed to have been detected in scanning
tunneling microscopy (STM) conductance maps of the pseudogap states of the
cuprate high-temperature superconductor Bi2Sr2CaCu2O8+x (Bi-2212). We
investigate the influence of anisotropic STM tip structures on such
measurements and establish, with a model calculation, the presence of a
tunneling interference effect within an STM junction that induces
energy-dependent symmetry-breaking features in the conductance maps. We
experimentally confirm this phenomenon on different correlated electron
systems, including measurements in the pseudogap state of Bi-2212, showing that
the apparent nematic behavior of the imaged crystal lattice is likely not due
to nematic order but is related to how a realistic STM tip probes the band
structure of a material. We further establish that this interference effect can
be used as a sensitive probe of changes in the momentum structure of the
sample's quasiparticles as a function of energy.Comment: Accepted for publication (PRB - Rapid Communications). Main text (5
pages, 4 figures) + Supplemental Material (4 pages, 4 figures
Field-Induced Magnetic States in the Metallic Rare-Earth Layered Triangular Antiferromagnet TbAuAlGe
Magnetic frustration in metallic rare earth lanthanides () with
-electrons is crucial for producing interesting magnetic phases with high
magnetic anisotropy where intertwined charge and spin degrees of freedom lead
to novel phenomena. Here we report on the magnetic, thermodynamic, and
electrical transport properties of TbAuAlGe. Tb ions form 2-dimensional
triangular lattice layers which stack along the crystalline -axis. The
magnetic phase diagram reveals multiple nearly degenerate ordered states upon
applying field along the magnetically easy -plane before saturation. The
magnetoresistance in this configuration exhibits intricate field dependence
that closely follows that of the magnetization while the specific heat reveals
a region of highly enhanced entropy, suggesting the possibility of a
non-trivial spin textured phase. For fields applied along the -axis (hard
axis), we find linear magnetoresistance over a wide range of fields. We compare
the magnetic properties and magnetoresistance with an isostructral
GdAuAlGe single crystals. These results identify TbAuAlGe as an
environment for complex quantum spin states and pave the way for further
investigations of the broader AuAlGe family of materials.Comment: 8 pages, 5 figure
One-Component Order Parameter in URuSi Uncovered by Resonant Ultrasound Spectroscopy and Machine Learning
The unusual correlated state that emerges in URuSi below T =
17.5 K is known as "hidden order" because even basic characteristics of the
order parameter, such as its dimensionality (whether it has one component or
two), are "hidden". We use resonant ultrasound spectroscopy to measure the
symmetry-resolved elastic anomalies across T. We observe no anomalies in
the shear elastic moduli, providing strong thermodynamic evidence for a
one-component order parameter. We develop a machine learning framework that
reaches this conclusion directly from the raw data, even in a crystal that is
too small for traditional resonant ultrasound. Our result rules out a broad
class of theories of hidden order based on two-component order parameters, and
constrains the nature of the fluctuations from which unconventional
superconductivity emerges at lower temperature. Our machine learning framework
is a powerful new tool for classifying the ubiquitous competing orders in
correlated electron systems
Magnetic-Field-Independent Ultrasonic Dispersions in the Magnetically Robust Heavy Fermion System SmOs4Sb12
Elastic properties of the filled skutterudite compound SmOsSb have
been investigated by ultrasonic measurements. The elastic constant
shows two ultrasonic dispersions at 15 K and 53 K
for frequencies between 33 and 316 MHz, which follow a Debye-type
formula with Arrhenius-type temperature-dependent relaxation times, and remain
unchanged even with applied magnetic fields up to 10 T. The corresponding
activation energies were estimated to be = 105 K and = 409 K,
respectively. The latter, , is the highest value reported so far in the
Sb-based filled skutterudites. The presence of magnetically robust ultrasonic
dispersions in SmOsSb implies a possibility that an emergence of a
magnetically insensitive heavy fermion state in this system is associated with
a novel local charge degree of freedom which causes the ultrasonic dispersion.Comment: 5 pages, 4 figure
Theory-guided investigation on magnetic evolution of MnPtPdP and discovery of anti-CeCoIn-type ferromagnetic MnPdP
We report the magnetic changes from canted antiferromagnetic to ferromagnetic
orderings in anti-115-type MnPtPdP ( = 1, 2, 2.5, 3, 4, and 5)
and the discovery of a new rare-earth-free ferromagnet, MnPdP by both
theoretical prediction and experimental investigation. The family compounds
were synthesized using high temperature solid state method and characterized to
crystalize in the anti-CeCoIn type with the space group P4/mmm exhibiting a
two-dimensional layered structural feature. The magnetic property measurements
indicate that the compounds ordered from canted A-type antiferromagnet in
MnPtP to ferromagnet above the room temperature with varying degrees of
coercivity and magnetic moments in MnPdP by reducing the spin orbital
coupling. The results of the MnPtPdP have been analyzed in
comparison to the other candidates of the 151 family of Mn(Pt/Pd)(P/As) to
understand the complex structure-magnetism relationships
Observation of odd-parity superconductivity in UTe2
Symmetry properties of the order parameter are among the most fundamental
characteristics of a superconductor. The pairing symmetry of recently
discovered heavy fermion superconductor UTe2 featuring an exceedingly large
upper critical field has attracted a great deal of attention. Even though it is
widely believed that UTe2 possesses an odd-parity, spin-triplet pairing
symmetry, direct evidence for it is lacking, especially at zero or low magnetic
fields. We report here the selection-rule results of Josephson coupling between
In, an s-wave superconductor, and UTe2. The orientation dependence of the
Josephson coupling suggests very strongly that UTe2 possess an odd-parity
pairing state of B_1u in zero magnetic fields. We also report the formation of
Andreev surface bound states on the (1-10) surface of UTe2.Comment: 16 pages, 4 figures, 2 table
- …