Lifshitz transition enabling superconducting dome around the quantum critical point in TiSe${}_2$

Abstract

Superconductivity often emerges as a dome around a quantum critical point (QCP) where long-range order is suppressed to zero temperature. So far, this has been mostly studied in magnetically ordered materials. By contrast, the interplay between charge order and superconductivity at a QCP is not fully understood. Here, we present resistance measurements proving that a dome of superconductivity surrounds the charge-density-wave (CDW) QCP in pristine samples of 1$T$-TiSe${}_2$ tuned with hydrostatic pressure. Furthermore, we use quantum oscillation measurements to show that the superconductivity sets in at a Lifshitz transition in the electronic band structure. We use density functional theory to identify the Fermi pockets enabling superconductivity: large electron and hole pockets connected by the CDW wave vector $\vec{Q}$ which emerge upon partial suppression of the zero-pressure CDW gap. Hence, we conclude that superconductivity is of interband type enabled by the presence of hole and electron bands connected by the CDW $\vec{Q}$ vector. Earlier calculations show that interband interactions are repulsive, which suggests that unconventional s${}_{\pm }$ superconductivity is realised in TiSe${}_2$ - similar to the iron pnictides. These results highlight the importance of Lifshitz transitions in realising unconventional superconductivity and help understand its interaction with CDW order in numerous materials.

arXiv comment21 pages, 5 figures

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Cited by in corpus (5)

• Charge-density-wave quantum critical point under pressure in 2$H$-TaSe${}_2$
• Electron-phonon-dominated charge-density-wave fluctuations in TiSe${}_2$ accessed by ultrafast nonequilibrium dynamics
• Emergent Pair Density Wave Order Across a Lifshitz Transition
• $H$-linear magnetoresistance in NbSe${}_2$ due to impeded cyclotron motion
• Direct evidence for two-gap superconductivity in hydrogen-intercalated titanium diselenide