Ferroelectric domain walls exhibit a range of interesting electrical properties and are now widely recognized as functional two-dimensional systems for the development of next-generation nanoelectronics. A major achievement in the field was the devel
opment of a fundamental framework that explains the emergence of enhanced electronic direct-current (DC) conduction at the domain walls. In this Review, we discuss the much less explored behavior of ferroelectric domain walls under applied alternating-current (AC) voltages. We provide an overview of the recent advances in the nanoscale characterization that allow for resolving the dynamic responses of individual domain walls to AC fields. In addition, different examples are presented, showing the unusual AC electronic properties that arise at neutral and charged domain walls in the kilo- to gigahertz regime. We conclude with a discussion about the future direction of the field and novel application opportunities, expanding domain-wall based nanoelectronics into the realm of AC technologies.
Exponential tail bounds for sums play an important role in statistics, but the example of the $t$-statistic shows that the exponential tail decay may be lost when population parameters need to be estimated from the data. However, it turns out that if
Studentizing is accompanied by estimating the location parameter in a suitable way, then the $t$-statistic regains the exponential tail behavior. Motivated by this example, the paper analyzes other ways of empirically standardizing sums and establishes tail bounds that are sub-Gaussian or even closer to normal for the following settings: Standardization with Studentized contrasts for normal observations, standardization with the log likelihood ratio statistic for observations from an exponential family, and standardization via self-normalization for observations from a symmetric distribution with unknown center of symmetry. The latter standardization gives rise to a novel scan statistic for heteroscedastic data whose asymptotic power is analyzed.
Many researchers studying online social communities seek to make such communities better. However, understanding what better means is challenging, due to the divergent opinions of community members, and the multitude of possible community values whic
h often conflict with one another. Community members own values for their communities are not well understood, and how these values align with one another is an open question. Previous research has mostly focused on specific and comparatively well-defined harms within online communities, such as harassment, rule-breaking, and misinformation. In this work, we ask 39 community members on reddit to describe their values for their communities. We gather 301 responses in members own words, spanning 125 unique communities, and use iterative categorization to produce a taxonomy of 29 different community values across 9 major categories. We find that members value a broad range of topics ranging from technical features to the diversity of the community, and most frequently prioritize content quality. We identify important understudied topics such as content quality and community size, highlight where values conflict with one another, and call for research into governance methods for communities that protect vulnerable members.
We aim to make use of the measurements from the Giraffe Inner Bulge Survey (GIBS) and the Gaia$-$ESO survey (GES) to study the kinematics and distance of the carrier of DIB$,lambda$8620, as well as other properties. We successfully detected and measu
red DIB$,lambda$8620 in 760 of 4117 GES spectra. Combined with the DIBs measured in GIBS spectra, we confirmed a tight relation between EW and $E(J-K_{rm S})$ as well as $A_{rm V}$, with similar fitting coefficients to those found by previous works. With a more accurate sample and the consideration of the solar motion, the rest-frame wavelength of DIB$,lambda$8620 was redetermined as 8620.83 r{A}, with a mean fit error of 0.36 r{A}. We studied the kinematics of the DIB carriers by tracing their median radial velocities in each field in the local standard of rest ($V_{rm LSR}$) and into the galactocentric frame ($V_{rm GC}$), respectively, as a function of the Galactic longitudes. Based on the median $V_{rm LSR}$ and two Galactic rotation models, we obtained valid kinematic distances of the DIB carriers for nine GIBS and ten GES fields. We also found a linear relation between the DIB$,lambda$8620 measured in this work and the near-infrared DIB in APOGEE spectra at $1.5273,mu m$. We demonstrate that the DIB carriers can be located much closer to the observer than the background stars based on the following arguments: (i) qualitatively, the carriers occupy in the Galactic longitude$-$velocity diagram typical rotation velocities of stars in the local Galactic disk, while the background stars in the GIBS survey are mainly located in the Galactic bulge; (ii) quantitatively, all the derived kinematic distances of the DIB carriers are smaller than the median distances to background stars in each field.
We count the numbers of primitive periodic orbits on families of 4-regular directed circulant graphs with $n$ vertices. The relevant counting techniques are then extended to count the numbers of primitive pseudo orbits (sets of distinct primitive per
iodic orbits) up to length $n$ that lack self-intersections, or that never intersect at more than a single vertex at a time repeated exactly twice for each self-intersection (2-encounters of length zero), for two particular families of graphs. We then regard these two families of graphs as families of quantum graphs and use the counting results to compute the variance of the coefficients of the quantum graphs characteristic polynomial.
Unconventional superconductors are of high interest due to their rich physics, a topical example being topological edge-states associated with $p$-wave superconductivity. A practical obstacle in studying such systems is the very low critical temperat
ure $T_text{c}$ that is required to realize a $p$-wave superconducting phase in a material. We predict that the $T_text{c}$ of an intrinsic $p$-wave superconductor can be significantly enhanced by coupling it via an atomically thin ferromagnetic layer (F) to a conventional $s$-wave or a $d$-wave superconductor with a higher critical temperature. We show that this $T_text{c}$-boost is tunable via the direction of the magnetization in F. Moreover, we show that the enhancement in $T_text{c}$ can also be achieved using the Zeeman-effect of an external magnetic field. Our findings provide a way to increase $T_text{c}$ in $p$-wave superconductors in a controllable way and make the exotic physics associated with such materials more easily accessible experimentally.
While deep learning has revolutionized research and applications in NLP and computer vision, this has not yet been the case for behavioral modeling and behavioral health applications. This is because the domains datasets are smaller, have heterogeneo
us datatypes, and typically exhibit a large degree of missingness. Therefore, off-the-shelf deep learning models require significant, often prohibitive, adaptation. Accordingly, many research applications still rely on manually coded features with boosted tree models, sometimes with task-specific features handcrafted by experts. Here, we address these challenges by providing a neural architecture framework for mobile sensing data that can learn generalizable feature representations from time series and demonstrates the feasibility of transfer learning on small data domains through finetuning. This architecture combines benefits from CNN and Trans-former architectures to (1) enable better prediction performance by learning directly from raw minute-level sensor data without the need for handcrafted features by up to 0.33 ROC AUC, and (2) use pretraining to outperform simpler neural models and boosted decision trees with data from as few a dozen participants.
To harness technological opportunities arising from optically controlled quantum many-body states a deeper theoretical understanding of driven-dissipative interacting systems and their nonequilibrium phase transitions is essential. Here we provide nu
merical evidence for a dynamical phase transition in the nonequilibrium steady state of interacting magnons in the prototypical two-dimensional Heisenberg antiferromagnet with drive and dissipation. This nonthermal transition is characterized by a qualitative change in the magnon distribution, from subthermal at low drive to a generalized Bose-Einstein form including a nonvanishing condensate fraction at high drive. A finite-size analysis reveals static and dynamical critical scaling, with a discontinuous slope of the magnon number versus driving field strength and critical slowing down at the transition point. Implications for experiments on quantum materials and polariton condensates are discussed.
The recent observation of high-lying Rydberg states of excitons in semiconductors with relatively high binding energy motivates exploring their applications in quantum nonlinear optics and quantum information processing. Here, we study Rydberg excita
tion dynamics of a mesoscopic array of excitons to demonstrate its application in simulation of quantum many-body dynamics. We show that the $mathbb{Z}_2$-ordered phase can be reached using physical parameters available for cuprous oxide (Cu$_2$O) by optimizing driving laser parameters such as duration, intensity, and frequency. In an example, we study the application of our proposed system to solving the Maximum Independent Set (MIS) problem based on the Rydberg blockade effect.
