arXiv subjects

J. Y. Zeng

Publications and source records attributed to J. Y. Zeng.

4 recordsLinked to original sources

arXiv2020

Intrinsic mechanism for anisotropic magnetoresistance and experimental confirmation in Co$_x$Fe$_{1-x}$ single-crystal films

Using first-principles transport calculations, we predict that the anisotropic magnetoresistance (AMR) of single-crystal Co$_x$Fe$_{1-x}$ alloys is strongly dependent on the current orientation and alloy concentration. An intrinsic mechanism for AMR is found to arise from the band crossing due to magnetization-dependent symmetry protection. These special $k$-points can be shifted towards or away from the Fermi energy by varying the alloy composition and hence the exchange splitting, thus allowing AMR tunability. The prediction is confirmed by delicate transport measurements, which further reveal a reciprocal relationship of the longitudinal and transverse resistivities along different crystal axes.

cond-mat.mtrl-sci↗

arXiv2019

Absence of magnetic thermal conductivity in the quantum spin liquid candidate EtMe3Sb[Pd(dmit)2]2 -- revisited

We present the ultralow-temperature specific heat and thermal conductivity measurements on single crystals of triangular-lattice organic compound EtMe$_3$Sb[Pd(dmit)$_2$]$_2$, which has long been considered as a gapless quantum spin liquid candidate. In specific heat measurements, a finite linear term is observed, consistent with the previous work [S. Yamashita $et$ $al.$, Nat. Commun. {\bf 2}, 275 (2011)]. However, we do not observe a finite residual linear term in the thermal conductivity measurements, and the thermal conductivity does not change in a magnetic field of 6 Tesla. These results are in sharp contrast to previous thermal conductivity measurements on EtMe$_3$Sb[Pd(dmit)$_2$]$_2$ [M. Yamashita $et$ $al.$ Science {\bf 328}, 1246 (2010)], in which a huge residual linear term was observed and attributed to highly mobile gapless excitations, likely the spinons of a quantum spin liquid. In this context, the true ground state of EtMe$_3$Sb[Pd(dmit)$_2$]$_2$ has to be reconsidered.

cond-mat.str-el↗

arXiv2011

Nuclear pairing reduction due to rotation and blocking

Nuclear pairing gaps of normally deformed and superdeformed nuclei are investigated using the particle-number conserving (PNC) formalism for the cranked shell model, in which the blocking effects are treated exactly. Both rotational frequency $ω$-dependence and seniority (number of unpaired particles) $ν$-dependence of the pairing gap $\tildeΔ$ are investigated. For the ground-state bands of even-even nuclei, PNC calculations show that in general $\tildeΔ$ decreases with increasing $ω$, but the $ω$-dependence is much weaker than that calculated by the number-projected Hartree-Fock-Bogolyubov approach. For the multiquasiparticle bands (seniority $ν> 2$), the pairing gaps keep almost $ω$-independent. As a function of the seniority $ν$, the bandhead pairing gaps $\tildeΔ(ν,ω=0)$ decrease slowly with increasing $ν$. Even for the highest seniority $ν$ bands identified so far, $\tildeΔ(ν,ω=0)$ remains greater than 70% of $\tildeΔ(ν=0,ω=0)$.

nucl-th↗

arXiv2001

Isospin and Z$^{1/3}$ Dependence of the Nuclear Charge Radii

Based on the systematic investigation of the data available for $A \geq 40$, a $Z^{1/3}$ dependence for the nuclear charge radii is shown to be superior to the generally accepted $A^{1/3}$ law. A delicate scattering of data around $R_c/Z^{1/3}$ is infered as owing to the isospin effect and a linear dependence of $R_c/Z^{1/3}$ on $N/Z$ (or $(N-Z)/2$) is found. This inference is well supported by the microscopic Relativistic Continuum Hartree-Bogoliubov (RCHB) calculation conducted for the proton magic Ca, Ni, Zr, Sn and Pb isotopes including the exotic nuclei close to the neutron drip line. With the linear isospin dependence provided by the data and RCHB theory, a new isospin dependent $Z^{1/3}$ formula for the nuclear charge radii is proposed.

nucl-th↗