arXiv subjects

Zhenkai Xie

Publications and source records attributed to Zhenkai Xie.

5 recordsLinked to original sources

arXiv2026

Emergent interweaved CDW unoccupied states in hole-doping LaTe2 with element substitution

Multiple CDW-ordered layered rare-earth tellurides have increasingly emerged as a research hotspot, owing to their unconventional CDW formation, high transition temperature, and confirmed existence of axial Higgs modes. Recently, interweaved CDW in LaTe2 and its element-substituted phase LaTe2-xSbx have been investigated through TEM and ARPES measurements, revealing their distinct origins. Nevertheless, several complex diffraction features observed in TEM patterns remain unelucidated. In this work, we carried out scanning tunneling microscopy (STM) on LaTe1.6Sb0.4 crystals at 9 K. Three interweaved CDW wave vectors, q1=8/11a*, q2=5/11a* and q3=3/11a* were observed, which are induced by hole doping in unoccupied states. The q1 and q3 are theoretically verified to be nesting vectors connecting px- and py- bands. Furthermore, the satellite spots relative to the main Bragg spots p corresponding to a 11-a-superlattice have also been detected. Our findings provide critical insights for further exploring the origin of the interweaved CDW in hole/electron doping materials.

cond-mat.str-el↗

arXiv2024

Weakly Coupled Type-II Superconductivity in a Laves compound ZrRe2

We present a comprehensive investigation of the superconducting properties of ZrRe2, a Re-based hexagonal Laves compounds. ZrRe2 crystallizes in a C14-type structure (space group P63/mmc), with cell parameters a=b=5.2682(5) and c=8.63045 . Resistivity and magnetic susceptibility data both suggest that ZrRe2 exhibits a sharp superconducting transition above 6.1 K. The measured lower and upper critical fields are 6.27 mT and 12.77 T, respectively, with a large upper critical field that approached the Pauli limit.Measurements of the heat capacity confirm the presence of bulk superconductivity, with a normalized specific heat change of 1.24 and an electron-phonon strength of 0.69 . DFT calculations revealed that the band structure of ZrRe2 is intricate and without van-Hove singularity. The observed large specific heat jump, combined with the electron-phonon strength , suggests that ZrRe2 is a weakly coupled type II superconductor.

cond-mat.supr-con↗

arXiv2023

High quality and wafer-scale cubic silicon carbide single crystals

Silicon carbide (SiC) is an important semiconductor material for fabricating power electronic devices that exhibit higher switch frequency, lower energy loss and substantial reduction both in size and weight in comparison with its Si-based counterparts1-4. Currently, most devices, such as metal-oxide-semiconductor field effect transistors, which are core devices used in electric vehicles, photovoltaic industry and other applications, are fabricated on a hexagonal polytype 4H-SiC because of its commercial availability5. Cubic silicon carbide (3C-SiC), the only cubic polytype, has a moderate band gap of 2.36 eV at room-temperature, but a superior mobility and thermal conduction than 4H-SiC4,6-11. Moreover, the much lower concentration of interfacial traps between insulating oxide gate and 3C-SiC helps fabricate reliable and long-life devices7-10,12-14. The growth of 3C-SiC crystals, however, has remained a challenge up to now despite of decades-long efforts by researchers because of its easy transformation into other polytypes during growth15-19, limiting the 3C-SiC based devices. Here, we report that 3C-SiC can be made thermodynamically favored from nucleation to growth on a 4H-SiC substrate by top-seeded solution growth technique(TSSG), beyond what's expected by classic nucleation theory. This enables the steady growth of quality and large sized 3C-SiC crystals (2~4-inch in diameter and 4.0~10.0 mm in thickness) sustainable. Our findings broaden the mechanism of hetero-seed crystal growth and provide a feasible route to mass production of 3C-SiC crystals,offering new opportunities to develop power electronic devices potentially with better performances than those based on 4H-SiC.

cond-mat.mtrl-sci↗

arXiv2022

A revisit of superconductivity in 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ single crystals

Previous investigations of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ mainly focused on the direct competition between superconductivity and charge density wave (CDW). However, the superconductivity itself, although has been prominently enhanced by isovalent Se substitution, has not been adequately investigated. Here, we performed a detailed electrical transport measurement down to 0.1 K on a series of 4$H_b$-TaS$_{2-2x}$Se$_{2x}$ single crystals. A systematic fitting of the temperature-dependent resistance demonstrates that the decreased Debye temperatures ($Θ_{D}$) and higher electron-phonon coupling constants ($λ_{e-p}$) at the optimal Se doping content raise the superconducting transition temperature ($T_c$). Additionally, we discovered that the incorporation of Se diminishes the degree of anisotropy of the superconductivity in the highly layered structure. More prominently, a comprehensive analysis of the vortex liquid phase region reveals that the optimally doped sample deviates from the canonical 2D Tinkham prediction but favors a linear trend with the variation of the external magnetic field. These findings emphasize the importance of interlayer interaction in this segregated superconducting-Mott-insulating system.

cond-mat.supr-con↗

arXiv2022

Pressure-induced superconductivity in charge-density-wave compound LaTe2-xSbx (x=0 and 0.4)

Here, we have grown single crystals of LaTe2-xSbx (x=0 and 0.4) with continuously adjustable CDW. High-pressure x-ray diffraction show LaTe2 does not undergo phase transition and keep robust below 40 GPa. In-situ high-pressure electrical measurements show LaTe2-xSbx undergo semiconductor-metal-superconductivity transition at 4.6 and 2.5 GPa, respectively. With the doping of Sb, the highest Tc increases from 4.6 to 6.5 K. Theoretical calculations reveal that the CDW has been completely suppressed and the calculated Tc is about 2.97 K at 4.5 GPa, consistent with the measured value. Then, the pressure-induced superconductivity in LaTe2-xSbx can be explained in the framework of the BCS theory.

cond-mat.supr-con↗