Manipulating chiral-spin transport with ferroelectric polarization

A collective excitation of the spin structure in a magnetic insulator can transmit spin-angular momentum with negligible dissipation. This quantum of a spin wave, introduced more than nine decades ago, has always been manipulated through magnetic dipoles, (i.e., timereversal symmetry). Here, we report the experimental observation of chiral-spin transport in multiferroic BiFeO3, where the spin transport is controlled by reversing the ferroelectric polarization (i.e., spatial inversion symmetry). The ferroelectrically controlled magnons produce an unprecedented ratio of up to 18% rectification at room temperature. The spin torque that the magnons in BiFeO3 carry can be used to efficiently switch the magnetization of adja-cent magnets, with a spin-torque efficiency being comparable to the spin Hall effect in heavy metals. Utilizing such a controllable magnon generation and transmission in BiFeO3, an alloxide, energy-scalable logic is demonstrated composed of spin-orbit injection, detection, and magnetoelectric control. This observation opens a new chapter of multiferroic magnons and paves an alternative pathway towards low-dissipation nanoelectronics

Synthesis of alloys and lateral heterostructures of atomically thin transition-metal dichalcogenides for optoelectronic applications

The development of novel material platforms is the driving force behind steady advancements in microelectronics and optical sciences. Demonstrating novel functionalities, achieving faster data processing speeds, and minimizing the power consumption are the most important figures of merit, which shape the research roadmap for the discovery of new applied materials. Along this venue, most often, combing heterogeneous material is the most viable approach for simultaneously achieving these figures of merit all in one single chip. Motivated by this precedent, the objective of my research is oriented towards the implementation of a holist material platform for the synthesis of atomically thin lateral heterostructures (HSs) with engineerable morphologies and tunable optoelectronic properties in addressable sites on an electron chip. Employing the multipotent transition-metal dichalcogenide (TMD) material system, I first establish a technique for the post-growth alloying of binary TMDs and then harness it for the synthesis of patterned lateral TMD HSs using a CMOS-compatible fabrication protocol. Following a complete set of spectroscopies and characterizations, I provide detailed insights into the HS synthesis mechanism and further discuss technical challenges and viable solutions. I believe the developed knowledge in my PhD research can find immediate applications in multiple technologies including quantum information-processing, wearable devices, and the next generation of optoelectronics.Ph.D

Controlled ovarian stimulation with r-FSH plus r-LH vs. HMG plus r-FSH in patients candidate for IVF/ICSI cycles: An RCT

Background: Different combination of gonadotropin preparation has been introduced with no definite superiority of one over others in in vitro fertilization (IVF), but individualized regimens for each patient are needed. Objective: The aim of the present study was to investigate the effect of controlled ovarian stimulation with recombinant- follicle stimulating hormone (r-FSH) plus recombinant-luteinizing hormone (rLH) versus human menopausal gonadotropin (HMG) plus r-FSH on fertility outcomes in IVF patients. Materials and Methods: This is a randomized clinical trial study that was performed from October 2014-April 2016 on 140 infertile patients with a set of inclusion criteria that referred to infertility clinics in Vali- asr and Gandhi Hospital in Tehran. The women were randomly divided into two treatment groups. The first group (n=70) received rFSH from the second day of cycle and was added HMG in 6th day and the 2nd group (n=70), received rFSH from the second day of cycle and was added recombinant-LH in 6th day. Then ovum Pick-Up and embryo transfer were performed. In this study, we assessed the outcomes such as; chemical and clinical pregnancy rate, live birth and abortion rate. Results: Number of follicles in ovaries, total number of oocytes or M2 oocytes and quality of fetuses has no significant differences between two groups (p>0.05). Total number of fetuses were significantly higher in patients who received rFSH + HMG (p=0.02). Fertility outcomes consisted of: live birth rate, chemical pregnancy and clinical pregnancy rate were higher in rFSH + HMG group in comparison to rFSH +r-LH group (p<0.05). Conclusion: It seems that in IVF patients, HMG + rFSH used for controlled ovarian hyperstimulation have better effects on fertility outcomes, but in order to verify the results, it is recommended to implement studies on more patients

Ultrafast Control of Phase and Polarization of Light Expedited by Hot-Electron Transfer

All-optical modulation is an entangled part of ultrafast nonlinear optics with promising impacts on tunable optical devices in the future. Current advancements in all-optical control predominantly offer modulation by means of altering light intensity, while the ultrafast manipulation of other attributes of light have yet to be further explored. Here, we demonstrate the active modulation of the phase, polarization, and amplitude of light through the nonlinear modification of the optical response of a plasmonic crystal that supports subradiant, high Q, and polarization-selective resonance modes. The designed mode is exclusively accessible via TM-polarized light, which enables significant phase modulation and polarization conversion within the visible spectrum. To tailor the device performance in the time domain, we exploit the ultrafast transport dynamics of hot electrons at the interface of plasmonic metals and charge acceptor materials to facilitate an ultrafast switching speed. In addition, the operating wavelength of the proposed device can be tuned through the control of the in-plane momentum of light. Our work reveals the viability of dynamic phase and polarization control in plasmonic systems for all-optical switching and data processing

Strain relaxation via formation of cracks in compositionally modulated two-dimensional semiconductor alloys

2D alloys: intrinsic strain in MoS2xSe2(1-x) ternary crystals Composition modulation synthesis of ternary alloys of atomically thin transition metal dichalcogenides gives rise to intrinsic biaxial strain. A team led by Ali Adibi at Georgia Institute of Technology reported the onset of a substantial biaxial strain in monolayer MoS2xSe2(1-x) that is intrinsically linked to the two-step composition modulation synthesis used to grow the ternary alloy. As the S atoms replace the Se atoms of the starting MoSe2 host crystal, the resulting alloy forms a stretched lattice and develops a large biaxial tensile strain. Morphological and spectroscopic characterisations suggest that such strain results in the onset of fracture in the crystal, and further relaxes via formation of cracks within the crystal domains. Theoretical modelling indicates that pre-existing cracks give a substantial contribution in weakening the strength of the synthesized van der Waals alloy