Synthesis, Structural, and Transport Properties of Cr-Doped BaTi₂As₂O

Abstract

Abstract:The interplay between unconventional superconductivity and the ordering of charge/spin density wave is one of the most vital issues in both condensed matter physics and material science. The Ti-based compound BaTi 2 As 2 O, which can be seen as the parent phase of superconducting BaTi 2 Sb 2 O, has a layered structure with a space group P4/mmm, similar to that of cuprate and iron-based superconductors. This material exhibits a charge density wave (CDW) ordering transition revealed by an anomaly at around 200 K in transport measurements. Here, we report the synthesis and systematical study of the physical properties in Cr-doped BaTi 2-x Cr x As 2 O (x = 0 -0.154), and demonstrate that the transition temperature of the CDW ordering is suppressed gradually by the doped Cr element. The magnetization measurements confirm the evolution of the CDW ordering transition. These observed behaviors are similar to that observed in iron-based superconductors, but no superconductivity emerges down to 2 K. In addition, the first-principles calculations are also carried out for well-understanding the nature of experimental observations.

Effects of electron correlation, electron-phonon coupling, and spin-orbit coupling on the isovalent Pd-substituted superconductorSrPt3P

“…We note that this is a common phenomenon in some chemical doped materials and such a saturated features has been reported elsewhere. [14] B. Superconducting Properties…”

Titanium Pnictide Oxide Superconductors

“…In contrast, in BaTi 2 As 2 O, electron doping by Li + intercalation has been reported as mentioned above. Recently, another electron doping system, Ba(Ti 1-x Cr x ) 2 As 2 O, has been synthesized where the T DW is gradually suppressed with increasing x and reaches 139 K at the solubility limit (x = 0.077) but no superconductivity is emerged [56]. These results may suggest electron-doping is not suitable for the superconductivity in titanium pnictide oxides.…”

Investigation into Structural Phase Transitions in Layered Titanium-Oxypnictides by a Computational Phonon Analysis

“…Recently discovered layered titanium-oxypnictides, ATi 2 Pn 2 O [A = Na 2 , Ba, (SrF) 2 , and (SmO) 2 ; Pn = As, Sb, and Bi], − comprise a new superconducting family, and this superconducting mechanism has attracted intensive attentions because the crystal and electronic structures are similar to those of exotic superconductors such as cuprates or iron arsenides . The superconducting mechanism has been expected to be electron–phonon driven, − and the accompanying singularities in resistivity and susceptibility at low temperature are regarded as being due to conventional charge density wave (CDW). ,− Though our latest phonon evaluation using GGA-PBE without assuming any magnetic orderings revealed that the singularities could be explained within the conventional CDW for Pn = As, it is still unknown if this is the case for Pn = Sb and Bi. , Interestingly, recent works are pointing out the possibility of exotic mechanism of the structural transition for these compounds: For BaTi 2 Pn 2 O (Pn = As and Sb), Frandsen et al reported the breaking of the 4-fold symmetry at low temperature without any superstructure peaks by neutron and electron diffractions and suggested the possibility of intra-unit-cell nematic CDW, which is observed in cuprates and iron arsenides superconductors, − to account for the breaking.…”