arXiv subjects

H. Meng

Publications and source records attributed to H. Meng.

6 recordsLinked to original sources

arXiv2025

On a class of involutive Yang-Baxter groups

A group is called an involutive Yang-Baxter group (IYB-group) if it is isomorphic to the permutation group of an involutive, non-degenerate set-theoretic solution of the Yang-Baxter equation. This paper investigates finite soluble groups whose Sylow subgroups have nilpotency class at most two, addressing Ced\'{o} and Okni\'{n}ski's question~\cite{CedoOkninski2025} of whether such groups are IYB-groups. We establish that a finite soluble group with Sylow subgroups of class at most two is an IYB-group if its nilpotent residual is $\Q_8$-free. We also prove that a finite soluble group with Sylow subgroups of class at most two and Sylow $2$-subgroups isomorphic to $Q_8$ is an IYB-group.

math.GR↗

arXiv2025

On finitely generated left nilpotent braces

A description of finitely generated left nilpotent braces of class at most two is presented in this paper. The description heavily depends on the fact that if $B$ is left nilpotent of class at most $2$, that is $B^3 = 0$, then $B$ is right nilpotent of class at most $3$, that is $B^{(4)} = 0$. In addition, we construct a free object in the category of finitely generated left nilpotent braces of class at most $2$.

math.GR↗

arXiv2024

Experimental demonstration of dark current mitigation by an over-inserted plug in a normal conducting VHF gun

The room temperature continuous wave (CW) very-high-frequency (VHF) gun is one of the candidates for the electron gun of the high-repetition-rate free-electron lasers (FELs). The VHF gun operates with a cathode gradient of ~ 20 MV/m and an accelerating voltage of ~ 750 kV. The gun dark current emission leads to beam loss along the FEL machine, therefore is a critical parameter for the performance of the CW gun. In this paper, we presents a systematic study of the dark current reduction of the VHF gun, including cathode region optimizations, dark current tracking simulations and measurements. Over-inserted cathode plugs were tested in two VHF guns of different acceleration gap sizes, and both demonstrated significant dark current reduction ratios of more than two orders of magnitude.

physics.acc-ph↗

arXiv2023

Adiabatic phase pumping in S/F/S hybrids with non-coplanar magnetization

We study the distinctive features of the phase pumping effect in Josephson transport through a three-layered ferromagnet F$_1$/F/F$_2$ with non-coplanar magnetization. Using Gor'kov and Bogoliubov-de Gennes formalisms we go beyond the quasiclassical approximation and analyze the dependence of the spontaneous Josephson phase $\psi$ on the exchange field $h$ in the F layer and details of magnetization profile. The pumping of the Josephson phase can be generated by the mutual rotation of magnetizations in F$_1$ and F$_2$ layers resulting in the nontrivial phase gain at the rotation period (Berry phase). The increase in $h$ is shown to cause changes in the topology of the phase evolution: the gain of the Josephson phase at the pumping period switches from $0$ to $2\pi$. We study the scenario of these switchings originating from the interplay between several competing local minima of the free energy of the junction versus the superconducting phase difference. Our analysis provides the basis for the search of experimental setup realizing the phase pumping phenomenon.

cond-mat.supr-con↗

arXiv2020

Magnetic Flux Pumping in Superconducting Loop Containing a Josephson $\psi$ Junction

We demonstrate that a Josephson junction with a half-metallic weak link integrated into the superconducting loop enables the pumping of magnetic flux piercing the loop. In such junctions, the ground state phase $\psi$ is determined by the mutual orientation of magnetic moments in two ferromagnets surrounding the half-metal. Thus, the precession of magnetic moment in one of two ferromagnets controlled, e.g., by the microwave radiation, results in the accumulation of the phase $\psi$ and subsequent switching between the states with different vorticities. The proposed flux pumping mechanism does not require the application of voltage or external magnetic field which enables the design of electrically decoupled memory cells in superconducting spintronics.

cond-mat.supr-con↗

arXiv2013

Electric-field-induced strain-mediated magnetoelectric effect in CoFeB-MgO magnetic tunnel junctions

Magnetoelectric coupling between magnetic and electric dipoles is one of the cornerstones of modern physics towards developing the most energy-efficient magnetic data storage. Conventionally, magnetoelectric coupling is achieved in single-phase multiferroics or in magnetoelectric composite nanostructures consisting of ferromagnetic and ferroelectric/piezoelectric materials. Here, we demonstrate an electric-field-induced strain-mediated magnetoelectric effect in ultrathin CoFeB/MgO magnetic tunnel junction employing non-piezoelectric material, which is a vitally important structure for spintronic devices, by using dynamical magnetoelectric and piezoresponse force microscopy measurement techniques. We show that the applied electric-field induces strain in a few atomic layers of dielectric MgO which is transferred to magnetostrictive CoFeB layer, resulting in a magnetoelectric effect of magnitude up to 80.8 V cm-1 Oe-1 under -0.5 V. The demonstrated strain-mediated magnetoelectric effect with an electric field in magnetic tunnel junctions is a significant step towards exploring magnetoelectrically controlled spintronic devices for low-power and high density magnetic data storage applications.

cond-mat.mes-hall↗