119 research outputs found
Balanced electron-hole transport in spin-orbit semimetal SrIrO3 heterostructures
Relating the band structure of correlated semimetals to their transport
properties is a complex and often open issue. The partial occupation of
numerous electron and hole bands can result in properties that are seemingly in
contrast with one another, complicating the extraction of the transport
coefficients of different bands. The 5d oxide SrIrO3 hosts parabolic bands of
heavy holes and light electrons in gapped Dirac cones due to the interplay
between electron-electron interactions and spin-orbit coupling. We present a
multifold approach relying on different experimental techniques and theoretical
calculations to disentangle its complex electronic properties. By combining
magnetotransport and thermoelectric measurements in a field-effect geometry
with first-principles calculations, we quantitatively determine the transport
coefficients of different conduction channels. Despite their different
dispersion relationships, electrons and holes are found to have strikingly
similar transport coefficients, yielding a holelike response under field-effect
and thermoelectric measurements and a linear, electronlike Hall effect up to 33
T.Comment: 5 pages, 4 figure
Inverse Proximity Effects at Spin-Triplet Superconductor-Ferromagnet Interface
We investigate inverse proximity effects in a spin-triplet superconductor
(TSC) interfaced with a ferromagnet (FM), assuming different types of magnetic
profiles and chiral or helical pairings. The region of the coexistence of
spin-triplet superconductivity and magnetism is significantly influenced by the
orientation and spatial extension of the magnetization with respect to the spin
configuration of the Cooper pairs, resulting into clearcut anisotropy
signatures. A characteristic mark of the inverse proximity effect arises in the
induced spin-polarization at the TSC interface. This is unexpectedly stronger
when the magnetic proximity is weaker, thus unveiling immediate detection
signatures for spin-triplet pairs. We show that an anomalous magnetic proximity
can occur at the interface between the itinerant ferromagnet, SrRuO, and
the unconventional superconductor SrRuO. Such scenario indicates the
potential to design characteristic inverse proximity effects in experimentally
available SrRuO-SrRuO heterostructures and to assess the occurrence
of spin-triplet pairs in the highly debated superconducting phase of
SrRuO.Comment: 11 pages, 6 figure
Coupling charge and topological reconstructions at polar oxide interfaces
In oxide heterostructures, different materials are integrated into a single
artificial crystal, resulting in a breaking of inversion-symmetry across the
heterointerfaces. A notable example is the interface between polar and
non-polar materials, where valence discontinuities lead to otherwise
inaccessible charge and spin states. This approach paved the way to the
discovery of numerous unconventional properties absent in the bulk
constituents. However, control of the geometric structure of the electronic
wavefunctions in correlated oxides remains an open challenge. Here, we create
heterostructures consisting of ultrathin SrRuO, an itinerant ferromagnet
hosting momentum-space sources of Berry curvature, and LaAlO, a polar
wide-bandgap insulator. Transmission electron microscopy reveals an atomically
sharp LaO/RuO/SrO interface configuration, leading to excess charge being
pinned near the LaAlO/SrRuO interface. We demonstrate through
magneto-optical characterization, theoretical calculations and transport
measurements that the real-space charge reconstruction modifies the
momentum-space Berry curvature in SrRuO, driving a reorganization of the
topological charges in the band structure. Our results illustrate how the
topological and magnetic features of oxides can be manipulated by engineering
charge discontinuities at oxide interfaces.Comment: 5 pages main text (4 figures), 29 pages of supplementary informatio
Topologically-Driven Linear Magnetoresistance in Helimagnetic FeP
The helimagnet FeP is part of a family of binary pnictide materials with the
MnP-type structure which share a nonsymmorphic crystal symmetry that preserves
generic band structure characteristics through changes in elemental
composition. It shows many similarities, including in its magnetic order, to
isostructural CrAs and MnP, two compounds that are driven to superconductivity
under applied pressure. Here we present a series of high magnetic field
experiments on high quality single crystals of FeP, showing that the resistance
not only increases without saturation by up to several hundred times its zero
field value by 35 T, but that it also exhibits an anomalously linear field
dependence over the entire field range when the field is aligned precisely
along the crystallographic c-axis. A close comparison of quantum oscillation
frequencies to electronic structure calculations links this orientation to a
semi-Dirac point in the band structure which disperses linearly in a single
direction in the plane perpendicular to field, a symmetry-protected feature of
this entire material family. We show that the two striking features of MR-large
amplitude and linear field dependence-arise separately in this system, with the
latter likely due to a combination of ordered magnetism and topological band
structure.Comment: 10 pages, 6 figure
Scale-Free model for governing universe dynamics
We investigate the effects of scale-free model on cosmology, providing, in
this way, a statistical background in the framework of general relativity. In
order to discuss properties and time evolution of some relevant universe
dynamical parameters (cosmographic parameters), such as (Hubble
parameter), (deceleration parameter), (jerk parameter) and
(snap parameter), which are well re-defined in the framework of scale-free
model, we analyze a comparison between WMAP data. Hence the basic purpose of
the work is to consider this statistical interpretation of mass distribution of
universe, in order to have a mass density dynamics, not inferred from
Friedmann equations, via scale factor . This model, indeed, has been used
also to explain a possible origin and a viable explanation of cosmological
constant, which assumes a statistical interpretation without the presence of
extended theories of gravity; hence the problem of dark energy could be
revisited in the context of a classical probability distribution of mass, which
is, in particular, for the scale-free model, , with
. The CDM model becomes, with these considerations, a
consequence of the particular statistics together with the use of general
relativity.Comment: 7 pages, 4 figure
Electronic Band Structure Changes across the Antiferromagnetic Phase Transition of Exfoliated MnPS3 Flakes Probed by μ-ARPES
Exfoliated magnetic 2D materials enable versatile tuning of magnetization, e.g., by gating or providing proximity-induced exchange interaction. However, their electronic band structure after exfoliation has not been probed, presumably due to their photochemical sensitivity. Here, we provide micrometer-scale angle-resolved photoelectron spectroscopy of the exfoliated intralayer antiferromagnet MnPS3 above and below the Néel temperature down to one monolayer. Favorable comparison with density functional theory calculations enables identifying the orbital character of the observed bands. Consistently, we find pronounced changes across the Néel temperature for bands consisting of Mn 3d and 3p levels of adjacent S atoms. The deduced orbital mixture indicates that the superexchange is relevant for the magnetic interaction. There are only minor changes between monolayer and thicker films, demonstrating the predominant 2D character of MnPS3. The novel access is transferable to other MPX3 materials (M: transition metal, P: phosphorus, X: chalcogenide), providing several antiferromagnetic arrangements
Exchange interactions of CaMnO3 in the bulk and at the surface
We present electronic and magnetic properties of CaMnO3 (CMO) as obtained from ab initio calculations. We identify the preferable magnetic order by means of density functional theory plus Hubbard U calculations and extract the effective exchange parameters (Jij's) using the magnetic force theorem. We find that the effects of geometrical relaxation at the surface as well as the change of crystal field are very strong and are able to influence the lower-energy magnetic configuration. In particular, our analysis reveals that the exchange interaction between the Mn atoms belonging to the surface and the subsurface layers is very sensitive to the structural changes. An earlier study [A. Filippetti and W. E. Pickett, Phys. Rev. Lett. 83, 4184 (1999)PRLTAO0031-900710.1103/PhysRevLett.83.4184] suggested that this coupling is ferromagnetic and gives rise to the spin-flip (SF) process on the surface of CMO. In our work, we confirm their finding for an unrelaxed geometry, but once the structural relaxations are taken into account, this exchange coupling changes its sign. Thus, we suggest that the surface of CMO should have the same G-type antiferromagnetic order as in the bulk. Finally, we show that the suggested SF can be induced in the system by introducing an excess of electrons. © 2017 American Physical Society
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