Experimental investigation on the crystal structure and superconductivity of germanium-intercalated 2H–NbSe2 system

IF 5.3 3区材料科学 Q2 MATERIALS SCIENCE, MULTIDISCIPLINARY

Materials Research Bulletin Pub Date : 2024-09-18 DOI:10.1016/j.materresbull.2024.113103

Junkun Yi , Menghu Zhou , Lewei Chen , Yunqing Shi , Yadong Gu , Binbin Ruan , Qingsong Yang , Genfu Chen , Zhian Ren

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Abstract

We report the structural and superconducting properties of Ge-intercalated 2H–NbSe₂ polycrystals. Ge_xNbSe₂ samples with nominal 0 ≤ x ≤ 0.1 crystallize in the space group P6₃/mmc with Ge disorderedly occupying the interlayer Se₆ octahedral interstices. Superconducting critical temperature T_c monotonically decreases from 7.2 K in NbSe₂ to 4.9 K in Ge_0.1NbSe₂. Studies on resistivity, magnetization and specific heat derive the superconducting- and normal-state parameters, indicating that the suppression of the two-gap superconductivity is mostly caused by the lowered electron-phonon coupling parameter λ_e-p and density of states at the Fermi level N(E_F). Surprisingly, the upper critical field H_c2 and irreversible field H_irr of the low Ge-level samples are enhanced compared with those of the undoped one, which may ascribe to the electron scattering and vortex pinning by nonmagnetic Ge. This study suggests the feasibility for improving high-field performance by slight impurity doping and advances the understanding of superconductivity in transition-metal dichalcogenides.

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锗掺杂 2H-NbSe2 系统晶体结构和超导性的实验研究

我们报告了掺杂 Ge 的 2H-NbSe2 多晶体的结构和超导特性。标称 0 ≤ x ≤ 0.1 的 GexNbSe2 样品在 P63/mmc 空间群中结晶，Ge 无序占据层间 Se6 八面体间隙。超导临界温度 Tc 从 NbSe2 的 7.2 K 单调下降到 Ge0.1NbSe2 的 4.9 K。对电阻率、磁化率和比热的研究得出了超导态和正常态参数，表明两隙超导性的抑制主要是由费米级 N(EF) 的电子-声子耦合参数λe-p 和状态密度降低造成的。令人惊讶的是，与未掺杂样品相比，低Ge电平样品的上临界磁场Hc2和不可逆磁场Hirr得到了增强，这可能是由于非磁性Ge的电子散射和涡旋钉扎作用。这项研究表明，通过轻微的杂质掺杂来提高高磁场性能是可行的，同时也加深了人们对过渡金属二卤化物超导性的理解。

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来源期刊

Materials Research Bulletin 工程技术-材料科学：综合

CiteScore

9.80

自引率

5.60%

发文量

372

审稿时长

42 days

期刊介绍： Materials Research Bulletin is an international journal reporting high-impact research on processing-structure-property relationships in functional materials and nanomaterials with interesting electronic, magnetic, optical, thermal, mechanical or catalytic properties. Papers purely on thermodynamics or theoretical calculations (e.g., density functional theory) do not fall within the scope of the journal unless they also demonstrate a clear link to physical properties. Topics covered include functional materials (e.g., dielectrics, pyroelectrics, piezoelectrics, ferroelectrics, relaxors, thermoelectrics, etc.); electrochemistry and solid-state ionics (e.g., photovoltaics, batteries, sensors, and fuel cells); nanomaterials, graphene, and nanocomposites; luminescence and photocatalysis; crystal-structure and defect-structure analysis; novel electronics; non-crystalline solids; flexible electronics; protein-material interactions; and polymeric ion-exchange membranes.