arXiv subjects

Weishu Liu

Publications and source records attributed to Weishu Liu.

22 records · Page 2Linked to original sources

arXiv2016

Funding acknowledgment analysis:Queries and Caveats

Thomson Reuters' Web of Science (WoS) began systematically collecting acknowledgment information in August 2008. Since then, bibliometric analysis of funding acknowledgment (FA) has been growing and has aroused intense interest and attention from both academia and policy makers. Examining the distribution of FA by citation index database, by language, and by acknowledgment type, we noted coverage limitations and potential biases in each analysis. We argue that in spite of its great value, bibliometric analysis of FA should be used with caution.

cs.DL↗

arXiv2014

Anomalous CDW ground state in Cu$_2$Se: a wave-like fluctuation of $\it{dc}$ I-V curve near 50 K

A charge density wave (CDW) ground state is observed in polycrystalline Cu$_2$Se below 125 K, which corresponds to an energy gap of 40.9 meV and an electron-phonon coupling constant of 0.6. Due to the polycrystalline structure, the Peierls transition process has been expanded to a wide temperature range from 90 to 160 K. The Hall carrier concentration shows a continuous decrease from 2.1$\times$10$^{20}$ to 1.6$\times$10$^{20}$ cm$^{-3}$ in the temperature range from 160 K to 80 K, while almost unchanged above 160 K and below 90 K. After entering the CDW ground state, a wave-like fluctuation was observed in the I-V curve near 50 K, which exhibits as a periodic negative differential resistivity in an applied electric field due to the current. We also investigated the doping effect of Zn, Ni, and Te on the CDW ground state. Both Zn and Ni doped Cu$_2$Se show a CDW character with increased energy gap and electron-phonon coupling constant, but no notable Peierls transition was observed in Te doped Cu$_2$Se. Similar wave-like I-V curve was also seen in Cu$_{1.98}$Zn$_{0.02}$Se near 40 K. The regular fluctuation in $\it{dc}$ I-V curve was not magnetic field sensitive, but temperature and sample size sensitive.

cond-mat.mtrl-sci↗

arXiv2013

Topological Effect of Surface Plasmon Excitation in Gapped Isotropic Topological Insulator Nanowires

We present a theoretical investigation of the surface plasmon (SP) at the interface between topologically non-trivial cylindrical core and topological-trivial surrounding material, from the axion electrodynamics and modified constitutive relations. We find that the topological effect always leads to a red-shift of SP energy, while the energy red-shift decreases monotonically as core diameter decreases. A qualitative picture based on classical perturbation theory is given to explain these phenomena, from which we also infer that in order to enhance the shift, the difference between the inverse of dielectric constants of two materials shall be increased. We also find that the surrounding magnetic environment suppresses the topological effect. All these features can be well described by a simple ansatz surface wave, which is in good agreement with full electromagnetic eigenmodes. In addition, bulk plasmon energy at ω_{P}=17.5\pm0.2eV for semiconducting Bi2Se3 nanoparticle is observed from high-resolution Electron Energy Loss Spectrum Image measurements.

cond-mat.mes-hall↗

arXiv2012

Transport Properties of Ni, Co, Fe, Mn Doped Cu0.01Bi2Te2.7Se0.3 for Thermoelectric Device Applications

Bi2Te3 based thermoelectric devices typically use a nickel layer as a diffusion barrier to block the diffusion of solder or copper atoms from the electrode into the thermoelectric material. Previous studies have shown degradation in the efficiency of these thermoelectric devices may be due to the diffusion of the barrier layer into the thermoelectric material. In this work Ni, Co, Fe, and Mn are intentionally doped into Cu0.01Bi2Te2.7Se0.3 in order to understand their effects on the thermoelectric material. Thermoelectric transport properties including the Seebeck coefficient, thermal conductivity, electrical resistivity, carrier concentration, and carrier mobility of Cu0.01Bi2Te2.7Se0.3 doped with 2 atomic percent M (M=Ni, Co, Fe, Mn) as Cu0.01Bi2Te2.7Se0.3M0.02, are studied in a temperature range of 5-525 K.

cond-mat.mtrl-sci↗