This PDF file contains the front matter associated with SPIE Proceedings Volume 12205, including the Title Page, Copyright information, Table of Contents, and Conference Committee Page.

We demonstrated that thin films of bismuth emit helicity-dependent terahertz-waves when illuminated with circularly polarized near-infrared femtosecond laser pulses from an oblique incidence. The helicity-dependent terahertz-wave appears only in the polarization perpendicular to the incident plane and is the most dominant contribution to terahertz emission in this polarization. By increasing the thickness of the film, the helicity-dependent terahertz-wave emission enhances significantly, taking a maximum at around 70-nm-thickness, which is well beyond the penetration depth of the near-infrared laser. From this thickness dependence, we identify the photoinduced inverse spin Hall effect as the most plausible mechanism behind the helicity-dependent terahertz emission. By lowering the temperature, we find a significant enhancement of the high-frequency component of the helicity-dependent terahertz-waves for the 30-nm-thick sample. The current dynamics are extracted from the terahertz-waves, and we find that the enhancement comes from the increasing photocurrent’s relaxation rate when the temperature is lowered. By considering two different spin relaxation mechanisms, namely the Elliott-Yafet mechanism and the D’yakonov-Perel’ mechanism, we attribute the sharp increase of the relaxation rate seen for the 30-nm-thick film to the D’yakonov-Perel’ mechanism. Our findings highlight the unique characteristics of bismuth as a beneficial platform for terahertz spintronics, and the potential of terahertz emission spectroscopy as a useful probe for ultrafast spin/charge dynamics.

The role of topological insulator (TI) bulk states in the the enormous spin torques recorded at TI/ferromagnet (FM) interfaces is poorly understood. Here we study spin torques due to TI bulk states focusing on magnetized TIs. We find that there is a novel spin transfer torque on an inhomogeneous magnetization, it is small in our idealized

A diverse set of novel materials, physical phenomena, logic/memory devices, and circuit/system options/concepts are being pursued globally to design and develop the next generations of information storage and processing platforms. Many of these potential options are vastly different compared to their conventional counterparts and cannot be used as drop-in replacements. This research should therefore include several levels of abstraction, and must take a holistic approach to truly leverage the benefits offered by the promising options. Among the emerging materials and devices, magnetic and multiferroic devices are of particular interest thanks to their non-volatility, density, energy efficiency and durability. This paper presents a co-design framework for magnetic materials, devices, and memory arrays based on a hierarchy of physical models. Two major categories of devices are considered: spin-orbit-torque (SOT) and magnetoelectric (ME) random access memories. Circuit compatible experimentally validated/calibrated physical models for such devices is presented and used to optimize material and device parameters to minimize energy/delay for read and write operations for various target error rates. Finally, novel SOT and ME based cell designs for ternary content-addressable memories (TCAM) are presented and their potential performance is quantified against their SRAM and FeFET based designs using a comprehensive modeling and benchmarking framework.

Typical demands for magnetic field sensor applications are high dynamic magnetic field ranges, ambient temperature operation, small dimensions, necessary for high spatial resolution, and low energy consumption. In the case of sensors for biomagnetic sensing very high requirements in case of sensitivity and limit of detection (LOD) in the pT/Hz^1/2 to fT/Hz^1/2 range arise.

Surface acoustic wave (SAW) sensors based on the delta E effect combine the advantages of small form factor, ambient temperature operation and high sensitivity. The SAW sensor consists of a piezoelectric quartz substrate, a silicon oxide layer and a magnetoelastic (Fe₉₀Co₁₀)₇₈Si₁₂B₁₀ layer, deposited on top of the oxide layer. Between interdigital transducers (IDTs) at the ports of the sensor, horizontal shear (Love) waves propagate. The oxide layer serves as a guiding layer. If an external magnetic field is applied, the magnetization alterations in the FeCoSiB layer are accompanied by changes of the shear modulus G and the wave propagation changes.

The phase change of a transmitted signal serves as a measure of a magnetic field. Very low phase noise read out electronics is required to detect the phase changes. Heterodyne and homodyne electronic read out circuits are equivalent in performance while homodyne systems are advantages in terms of monolithic integration.

The presented SAW sensors reach a high sensitivity with an LOD of 152 pT/Hz^1/2 at 10 Hz and 52 pT/Hz^1/2 at 100 Hz. ed signal serves as a measure of a magnetic field. Very low phase noise read out electronics is required to detect the phase changes.

The coupling of spin and charge in magnetic semiconductors lies at the heart of the field of spintronics and has attracted significant interest for new computing technologies. In this paper, we will review our recent progress in studying and controlling magneto-exciton coupling in the layered antiferromagnetic semiconductor CrSBr. The anisotropic Wannier-type excitons in this material serve as a sensor of the interlayer magnetic coupling. Using this exciton sensor, we found that the magnetic order is extremely tunable by the application of tensile strain, with a reversible AFM to FM transition occurring at large but experimentally feasible strains. These results establish CrSBr as an exciting platform for harnessing spin-charge-lattice coupling to the 2D limit.

The spin and valley physics in 2-dimensional van der Waals materials provides a unique platform for novel applications in spintronics and valleytronics. 2H phase transition metal dichalcogenides (TMD) monolayers possesses broken inversion symmetry and strong spin-orbit coupling, leading to a coupled spin and valley physics that makes them better candidates for these applications. For practical device applications, spin and valley Hall effect (SVHE) is a good way of charge to spin and charge to valley conversion, making the electrical generation of spin and valley polarization possible. While SVHE has been observed via optical measurements at cryotemperatures below 30 K, the behavior at elevated temperatures and thorough understanding of the data are still lacking. In this work we conduct spatial Kerr rotation (KR) measurements on monolayer tungsten diselenide (WSe₂) field effect transistors and study the electrical control and temperature dependence of SVHE. We image the distribution of the spin and valley polarization directly and find clear evidence of the spin and valley accumulation at the edges. We show that the SVHE can be electrically modulated by the gate and drain bias, and the polarization persists at elevated temperatures. We then conduct four-port electrical test reflection spectra measurement and use a drift-diffusion model to interpret the data and extract key parameters. A lower-bound spin/valley lifetime is predicted of 40 ns and a mean free path of 240 nm below 90 K. The spin/valley polarization on the edge is calculated to be ~4% at 45 K. WSe₂-on-hBN samples are prepared as well, and the KR measurements on these samples are discussed.

We demonstrate the use of external field protocols to control optical properties of quantum spins for optimized photon-mediated operations in quantum information processing. Specifically, we study two-photon interference operations between spectrally different quantum emitters with realistic control protocols. We show that, well beyond their idealized versions, appropriate external field protocols can suppress spectral diffusion, mitigate inhomogeneous broadening and restore photon indistinguishability between spectrally different quantum emitters. These protocols can play an important role in enabling more efficient light-matter interfaces that are essential for scalable quantum information processing platforms.

We numerically investigate characteristics of spin-controlled vertical-cavity surface-emitting lasers (spin-VCSELs) under injection locking by using spin-flip rate equations. Generation of a modulation sideband whose phase is correlated with an injected light into a spin-VCSEL, is an attractive application of spin-VCSELs to frequency-shifted local oscillators in coherent optical communication systems. Our results indicate that the spin polarization modulation with a high degree of spin polarization is important for efficient generation of strong modulation sideband. Additionally, matching the modulation frequency and polarization mode splitting in the spin-VCSEL contribute to achieve efficient and ideal single sideband generation.

Spin-VCSELs offer particularly rich polarization dynamics due to non-trivial interplay of spin-induced circular gain dichroism with microcavity-related linear anisotropies. One of their promising applications is a data transfer technology in which the information is carried by spin of electrons and photons, surpassing the standard intensity modulation technology in both speed and energy consumption. Over the years, modeling of spin-VCSELs has been basically monopolized by the so-called spin-flip model, which is however constructed assuming degenerate orthogonal modes. Moreover, any amplitude anisotropies are treated in a perturbative way using linear coupling terms. This can be misleading in case of gain anisotropies originating from QW strain or asymmetric light confinement. The situation is even more complicated in highly-birefringent devices such as grating-based spin-VCSELs, where the mode profile asymmetry leads to new coupling mechanisms of optical field components with opposite helicity. The aim of this work is to (i) explore the role of linear gain anisotropy in spin-VCSELs within the extended spin-flip model based on polarization-resolved coupled-mode theory and (ii) to further analyze the consequences of recently predicted coupling mechanisms appearing in highly-birefringent spin-VCSELs.

The Einstein-Podolsky-Rosen (EPR) paradox that argues for the incompleteness of quantum mechanics as a description of physical reality has been put to rest by John Bell’s famous theorem, which inspired numerous experimental tests and brought about further affirmations of quantum reality. Nevertheless, in his writings and public presentations, Richard Feynman never acknowledged the significance of Bell’s contribution to the resolution of the EPR paradox. In this paper, we discuss several variants of the Bell inequalities (including one that was specifically espoused by Feynman), and explore the ways in which they demolish the arguments in favor of local hidden-variable theories. We also examine the roots of Feynman’s attitude toward Bell’s theorem in the context of Feynman’s special perspective on quantum mechanics.