Pressure-driven dome-shaped superconductivity and electronic structural evolution in tungsten ditelluride (1501.07394v3)

Abstract: Tungsten ditelluride has attracted intense research interest due to the recent discovery of its large unsaturated magnetoresistance up to 60 Tesla. Motivated by the presence of a small, sensitive Fermi surface of 5d electronic orbitals, we boost the electronic properties by applying a high pressure, and introduce superconductivity successfully. Superconductivity sharply appears at a pressure of 2.5 GPa, rapidly reaching a maximum critical temperature (Tc) of 7 K at around 16.8 GPa, followed by a monotonic decrease in Tc with increasing pressure, thereby exhibiting the typical dome-shaped superconducting phase. From theoretical calculations, we interpret the low-pressure region of the superconducting dome to an enrichment of the density of states at the Fermi level and attribute the high-pressure decrease in Tc to possible structural instability. Thus, Tungsten ditelluride may provide a new platform for our understanding of superconductivity phenomena in transition metal dichalcogenides.

• The paper demonstrates that superconductivity in tungsten ditelluride emerges at 2.5 GPa and forms a dome-shaped phase diagram with a critical temperature of 7 K at 16.8 GPa.
• It employs high-pressure experiments and DFT calculations to reveal enhanced electron-phonon coupling and phonon softening as key drivers of the superconducting state.
• The findings suggest that pressure-induced electronic and structural modifications can be leveraged to design advanced superconducting devices in transition metal dichalcogenides.

Insights into Pressure-Driven Superconductivity in Tungsten Ditelluride

The paper of tungsten ditelluride (WTe$_2$) in the context of its pressure-induced superconducting capabilities represents a significant investigation into transition metal dichalcogenides (TMDs). The primary aim of this research was to examine how high-pressure conditions influence the electronic properties and superconductive behavior of WTe$_2$, a material previously noted for its unsaturated large magnetoresistance (MR) when subjected to high magnetic fields.

Experimental Findings and Phase Diagram

The experiments demonstrated that superconductivity emerges abruptly at a pressure of 2.5 GPa. The critical temperature ($T_c$) reaches a peak of 7 K at approximately 16.8 GPa before experiencing a decline, following a classic dome-shaped superconducting phase diagram. This dome-shaped behavior is common in unconventional superconductors, suggesting an intricate relationship between pressure and electronic structure changes.

Theoretical Interpretation and Electronic Structure

The research incorporated density functional theory (DFT) calculations to provide a theoretical basis for observed phenomena. At lower pressures, the increase in $T_c$ is attributed to an enhanced density of states at the Fermi level, suggesting a strengthening of the electron-phonon coupling mechanism. However, as pressure increases past 16.8 GPa, structural instability is proposed as a possible factor for the decline in $T_c$.

Structural and Electronic Transformations

The paper further details WTe$_2$’s anisotropic band structure, emphasizing the significant contribution of Te-5p and W-5d orbitals that extend spatially, making them highly sensitive to external pressures. The pressure-enhanced hybridization escalates the bandwidth and introduces new Fermi pockets, thereby increasing the electron density.

Interestingly, DFT calculations reveal phonon softening under high pressure, aligning with the observed structural abnormalities at high pressures. The research anticipates that a combination of enriched electronic states at the Fermi level and altered lattice phonon modes due to pressure may lead to the observed superconductivity.

Practical Implications and Future Considerations

The implications of this research are multifaceted. Practically, it highlights a route for inducing superconductivity in non-superconducting materials under ambient conditions through external pressure application. This insight can inform future work on designing pressure-or strain-based superconducting devices and understanding superconductivity in low-dimensional systems more broadly.

From a theoretical standpoint, the findings contribute to the understanding of the interplay between electronic structure, lattice dynamics, and superconductivity in TMDs. The observed pressure-induced superconductivity could spur the development of new theoretical models that integrate structural phase transitions within the context of conventional and unconventional superconductors.

In conclusion, tungsten ditelluride's pressure-driven dome-shaped superconductivity offers a compelling investigation into the mechanisms driving superconductivity in TMD materials. Ongoing research could elucidate finer details of the phase transition processes and improve the predictability of superconductive states in complex materials under varying conditions.