41 research outputs found
Strange bedfellows inside a superconductor
The discovery of superconducting cuprates in 1986 is considered a watershed moment in the study of superconductivity—not only because of their high superconducting temperatures (TC’s) but also on account of their highly exotic properties, which are still largely enigmatic (1). On page 1506 of this issue, Wahlberg et al. (2) bring insights into the intriguing physics of cuprates’ nonsuperconducting state by connecting two widely studied phenomena previously believed to be completely independent of each other: the linear resistivity of the strange metallic phase and charge density waves (CDWs)
Bosonic excitation spectra of superconducting and extracted from scanning tunneling spectra
A detailed interpretation of scanning tunneling spectra obtained on
unconventional superconductors enables one to gain information on the pairing
boson. Decisive for this approach are inelastic tunneling events. Due to the
lack of momentum conservation in tunneling from or to the sharp tip, those are
enhanced in the geometry of a scanning tunneling microscope compared to planar
tunnel junctions. This work extends the method of obtaining the bosonic
excitation spectrum by deconvolution from tunneling spectra to nodal -wave
superconductors. In particular, scanning tunneling spectra of slightly
underdoped with a of
and optimally doped with a
of reveal a resonance mode in their bosonic excitation
spectrum at and
respectively. In both cases, the
overall shape of the bosonic excitation spectrum is indicative of predominant
spin scattering with a resonant mode at and
overdamped spin fluctuations for energies larger than . To perform the
deconvolution of the experimental data, we implemented an efficient iterative
algorithm that significantly enhances the reliability of our analysis
Giant non-volatile electric field control of proximity induced magnetism in the spin-orbit semimetal SrIrO3
With its potential for drastically reduced operation power of information
processing devices, electric field control of magnetism has generated huge
research interest. Recently, novel perspectives offered by the inherently large
spin-orbit coupling of 5d transition metals have emerged. Here, we demonstrate
non-volatile electrical control of the proximity induced magnetism in SrIrO3
based back-gated heterostructures. We report up to a 700 % variation of the
anomalous Hall conductivity {\sigma}_AHE and Hall angle {\theta}_AHE as
function of the applied gate voltage Vg. In contrast, the Curie temperature TC
= 100K and magnetic anisotropy of the system remain essentially unaffected by
Vg indicating a robust ferromagnetic state in SrIrO3 which strongly hints to
gating-induced changes of the anomalous Berry curvature. The electric-field
induced ferroelectric-like state of SrTiO3 enables non-volatile switching
behavior of {\sigma}_AHE and {\theta}_AHE below 60 K. The large tunability of
this system, opens new avenues towards efficient electric-field manipulation of
magnetism.Comment: 13 pages, 5 figures, to be published in Advanced Functional Material
Direct Observation of Strong Anomalous Hall Effect and Proximity-induced Ferromagnetic State in SrIrO₃
The 5d iridium-based transition metal oxides have gained broad interest because of their strong spin-orbit coupling which favors new or exotic quantum electronic states. On the other hand, they rarely exhibit more mainstream orders like ferromagnetism due to generally weak electron-electron correlation strength. Here, we show a proximity-induced ferromagnetic (FM) state with TC ≈ 100 K and strong magnetocrystalline anisotropy in a SrIrO3 (SIO) heterostructure via interfacial charge transfer by using a ferromagnetic insulator in contact with SIO. Electrical transport allows to selectively probe the FM state of the SIO layer and the direct observation of a strong, intrinsic and positive anomalous Hall effect (AHE). For T ≤ 20 K, the AHE displays unusually large coercive and saturation field, a fingerprint of a strong pseudospin-lattice coupling. A Hall angle, σxyAHE/σxx, larger by an order of magnitude than in typical 3d metals and a FM net moment of about 0.1 μB/Ir, is reported. This emphasizes how efficiently the nontrivial topological band properties of SIO can be manipulated by structural modifications and the exchange interaction with 3d TMOs
Strange semimetal dynamics in SrIrO
The interplay of electronic correlations, multi-orbital excitations, and
strong spin-orbit coupling is a fertile ground for new states of matter in
quantum materials. Here, we report on a confocal Raman scattering study of
momentum-resolved charge dynamics from a thin film of semimetallic perovskite
. We demonstrate that the charge dynamics, characterized by a
broad continuum, is well described in terms of the marginal Fermi liquid
phenomenology. In addition, over a wide temperature regime, the inverse
scattering time is for all momenta close to the Planckian limit
. Thus, is a
semimetallic multi-band system that is as correlated as, for example, the
cuprate superconductors. The usual challenge to resolve the charge dynamics in
multi-band systems with very different mobilities is circumvented by taking
advantage of the momentum space selectivity of polarized electronic Raman
scattering. The Raman responses of both hole- and electron-pockets display an
electronic continuum extending far beyond 1000\icm (125 meV), much larger
than allowed by the phase space for creating particle-hole pairs in a regular
Fermi liquid. Analyzing this response in the framework of a memory function
formalism, we are able to extract the frequency dependent scattering rate and
mass enhancement factor of both types of charge carriers, which in turn allows
us to determine the carrier-dependent mobilities and electrical resistivities.
The results are well consistent with transport measurement and demonstrate the
potential of this approach to investigate the charge dynamics in multi-band
systems
From valence fluctuations to long-range magnetic order in EuPd(SiGe) single crystals
EuPdSi is a valence-fluctuating system undergoing a
temperature-induced valence crossover at K. We present the
successful single crystal growth using the Czochralski method for the
substitution series EuPd(SiGe), with substitution levels
. A careful determination of the germanium content revealed that
only half of the nominal concentration is build into the crystal structure.
From thermodynamic measurements it is established that is strongly
suppressed for small substitution levels and antiferromagnetic order from
stable divalent europium emerges for . The valence transition is
accompanied by a pronounced change of the lattice parameter of order 1.8%.
In the antiferromagnetically ordered state below K, we find sizeable
magnetic anisotropy with an easy plane perpendicular to the crystallographic c
direction. An entropy analysis revealed that no valence fluctuations are
present for the magnetically ordered materials. Combining the obtained
thermodynamic and structural data, we construct a concentration-temperature
phase diagram demonstrating a rather abrupt change from a valence-fluctuating
to a magnetically-ordered state in EuPd(SiGe)