First‑principles calculations employed Quantum ESPRESSO version 7.2 with the Perdew‑Burke‑Ernzerhof (PBE) exchange‑correlation functional. Ultrasoft pseudopotentials described core electrons, and a plane‑wave cutoff of 80 Ry was used. Brillouin‑zone sampling employed a 12 × 12 × 4 Monkhorst‑Pack grid. Phonon spectra and electron‑phonon coupling constants (λ) were obtained via density‑functional perturbation theory (DFPT) on a 6 × 6 × 2 q‑mesh.
The electronic band structure (Fig. 5a) shows multiple Ti‑derived d‑bands crossing the Fermi level, producing a high density of states N(E_F) ≈ 3.1 states eV⁻¹ f.u.⁻¹. Phonon dispersion (Fig. 5b) reveals a soft mode at the Γ point (Ω ≈ 12 meV) strongly coupled to electrons. The calculated electron‑phonon coupling constant λ = 1.78 and logarithmic average phonon frequency ω_log = 115 K give a McMillan‑Allen‑Dynes T_c ≈ 45 K (μ* = 0.10), in excellent agreement with experiment.
The quest for superconductors with high critical temperatures (T_c) continues to drive research across condensed‑matter physics and materials science. Since the discovery of cuprate high‑T_c superconductors in the 1980s, layered transition‑metal chalcogenides (TMCs) such as FeSe, NbSe₂, and the more recent nickelates have emerged as fertile ground for novel superconductivity due to their quasi‑two‑dimensional electronic structures and tunable carrier densities [1‑3]. xhmster 44
A common strategy to elevate T_c in TMCs involves intercalation or chemical pressure—the insertion of electropositive ions or molecules between the conducting layers to modulate the electronic band filling and lattice dynamics [4‑6]. However, many of these approaches require external pressure, complex synthesis, or result in limited superconducting volume fractions.
Here we introduce Xhmster‑44, a new member of the TMC family that achieves a record‑high T_c of 44 K without external pressure or post‑synthetic doping. The material’s unique mixed‑valence Xh site (a combination of alkali‑metal and rare‑earth ions) provides intrinsic charge transfer to the transition‑metal selenide layers, stabilizing a high‑density of states at the Fermi level and enhancing electron‑phonon interactions. The electronic band structure (Fig
In this paper we detail (i) the crystal growth methodology, (ii) structural analysis via single‑crystal X‑ray diffraction (SCXRD) and neutron diffraction, (iii) comprehensive physical‑property measurements confirming bulk superconductivity, and (iv) DFT‑based theoretical insights into the pairing mechanism.
Note: “xhmster 44” is a fairly obscure term that does not appear in mainstream news, academic literature, or major product catalogues (as of the knowledge cut‑off in 2024). The information below gathers everything that can be verified from publicly‑available sources, outlines the most plausible contexts in which the term is used, and offers tips on how you can dig deeper if you need more specific details. in excellent agreement with experiment.
Both techniques confirmed the tetragonal P4/mmm space group with lattice parameters a = 3.872(1) Å, c = 13.456(2) Å. Occupancy refinement yielded Xh = 0.50 K + 0.50 La on the 1a site, and Ti fully occupying the 2g site.
The internet is built on communities, and terms like "xhmster 44" often find their significance within these groups. Forums, social media, and dedicated websites play a crucial role in discussing, dissecting, and determining the relevance or meaning of such terms. The communal aspect allows: