Pressure-induced suppression of charge density wave and emergence of superconductivity in 1T−VSe2

Abstract

We report pressure evolution of charge density wave (CDW) order and emergence of superconductivity (SC) in 1T-VSe2 single crystal by studying resistance and magnetoresistance behavior under high pressure. With increasing quasi-hydrostatic pressure the CDW order enhances with increase of the ordering temperature up to 240K at 12 GPa. Upon further increase of pressure, the resistance anomaly due to CDW order gets suppressed drastically and superconductivity emerges at ∼15 GPa, with the onset critical temperature (Tc) ∼4K. The pressure dependence of Tc is found negligible, different from the significant increase or a dome-shape seen in iso-structural layered diselenide superconductors. The high pressure magnetoresistance and Hall measurements suggest successive electronic structural changes with Fermi surface modifications at 6 GPa and 12 GPa. From the observed negative magnetoresistance in this pressure range and absence of coexisting CDW and SC phases, we propose that intra-layer spin-fluctuation can play a role in the emergence of superconductivity in the high pressure phase. PACS numbers:Layered transition metal dichalcogenide (TMDC) compounds provide an ideal platform to explore exotic ground-state electronic orders by tuning the Fermi surface topology and many-body effects through various external stimulations. 1 Among these, 1T-structured correlated metals (e.g., 1T-TaS 2 , 1T-TaSe 2 , 1T-TiSe 2 and 1T-TiTe 2 ) have been extensively studied for understanding the mechanism of charge density wave (CDW) order at low temperature and its coexistence with superconductivity (SC) in some part of the phase diagram. 2-8 An unconventional (exciton or band-type Jahn-Teller) mechanism for the CDW ordering has been established in these compounds by several experimental and theoretical studies, rather than the conventional Fermi surface nesting mechanism. However, the underlying mechanism for superconductivity is not conclusive so far. In some systems, the dome-shaped superconducting window in the vicinity of the CDW suppressed quantum critical point (QCP) supports unconventional SC scenario where CDW amplitude fluctuation is believed to be responsible for the Cooper pair formation. [9][10][11] In some other systems phonon mediated (BCS type) SC appears in the phase diagram window (separated from the CDW region) that is believed to originate in phase-separated metallic domains. 12,13 1T-VSe 2 is one of the rare correlated metallic systems where three dimensional (3D) nesting of the Fermi surface gives rise to 3D-CDW ordering (having commensurate in-plane wave vector 0.25a* with an incommensurate out-of-plane component). [14][15][16][17] The CDW transition temperature (T CDW ) is ∼110K, as seen in resistivity and susceptibility measurements. 18,19 Due to weak nesting condition, the CDW distortion (amplitude) is small, making the superstructure bands not observable below T CDW in ARPES measurements . 15,16 Although the high resolution ARPES measurements on single crystal 1T-VSe 2 show the presence of only hole pocket (of V 3d...

Novel Superstructure-Phase Two-Dimensional Material 1T-VSe2 at High Pressure

“…The layers are linked with weak van der Waals forces allowing various creative materials-design possibilities, such as the intercalation of foreign atoms and molecules 13 , exfoliation of the sample to the desired number of layers 14,15 , as well as applications in electronic devices 16,17 . Intriguingly, recent studies of VSe 2 revealed dramatic changes in the CDW and new physical properties such as a pseudo-gap, Fermi arc, and emergent superconductivity [18][19][20][21] ; naturally, this motivates us to investigate the behavior of this material under high pressure.…”

“…In Figure 4, we plot the temperature-pressure dependent structural change from trigonal ̅ to monoclinic together with the CDW and superconductivity results from Ref. 21.…”

Recent Developments on Emerging Properties, Growth Approaches, and Advanced Applications of Metallic 2D Layered Vanadium Dichalcogenides

“…[ 32 ] VSe 2 nanosheets grown on mica substrates via a single‐step chemical vapor deposition showed the excellent metallic feature with conductivity of up to 10 6 S m −1 , which is 1–4 orders of magnitude greater than that of several conductive 2D materials. [ 38 ] 1T‐VSe 2 single crystals, with increasing quasi‐hydrostatic pressure up to 12 GPa CDW order enhances up to temperature of 240 K, but further increment in pressure(until 15 GPa) suppresses CDW ordering and emergence of superconductivity come into picture at a critical temperature of 4 K. [ 107 ] Resistivity measurements with a six‐terminal Hall bar devices showed increase in electrical resistivity with increase in temperature, indicating the metallic behavior of the VSe 2 nanosheets. Similarly, VTe 2 nanosheets show the metallic nature with electrical conductivity of 1.7 × 10 6 S m −1 at room temperature and is comparable with other metallic 2D materials.…”

Structural and Transport Properties of 1T-VSe2 Single Crystal Under High Pressures

“…As for the transport properties of 1T-VSe 2 under pressure, controversial results have been reported. Specifically, Sahoo et al reported that the CDW transition temperature (T CDW ) first increases marginally up to 5 GPa and then increases rapidly, and accompanying by nonhydrostatic pressure-induced suppression of CDW, superconductivity emerges at ∼15 GPa (Sahoo et al, 2020). However, soon after, Feng et al found that the CDW transition temperature was enhanced linearly by increasing pressure, reaching 358 K at 14.6 GPa and no superconducting transition is observed under quasi-hydrostatic pressure up to 29.6 GPa (Feng et al, 2020).…”

“…Obviously, the detailed properties of 1T-VSe 2 under pressure remain far from being well explored. In addition, in these reports, the pressures applied in the XRD, Raman, and resistance measurements are below 30-35 GPa (Friend et al, 1978;Sereika et al, 2020;Feng et al, 2020;Sahoo et al, 2020). For pressures above 35 GPa, the evolution of structural and transport properties are still unclear.…”