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TT: Fachverband Tiefe Temperaturen

TT 70: Correlated Electrons: Charge Order

TT 70.1: Vortrag

Freitag, 20. März 2020, 09:30–09:45, HSZ 103

Interplay of superconductivity and charge-density-wave in NbSe₂ at high pressures — •Owen Moulding, Israel Osmond, Takaki Muramatsu, and Sven Friedemann — University of Bristol, Bristol, UK

The transition metal dichalcogenide NbSe₂ has well-documented charge density wave (CDW) and superconducting transitions at 33 K and 7 K at ambient pressure. The CDW transition is suppressed under high pressure and is absent beyond its quantum critical point (QCP). The effect of this QCP on superconductivity is of great interest and stimulates discussions on the relation between superconductivity and the CDW order. So far, resistivity, magnetic susceptibility, and X-ray measurements have explored the vicinity of this QCP and they indicate a weak relation between superconductivity and the CDW: either a weak competition between CDW order and superconductivity or a weak promotion of superconductivity by fluctuations at the CDW QCP.

Here, we present high-pressure Hall effect measurements as a clear probe of the CDW order and trace the CDW transition to higher pressures than previously measured with transport methods. The sign-change in the Hall coefficient marking the CDW transition is suppressed. Above the critical pressure of the CDW, the Hall effect remains hole-like consistent as observed by ARPES. We observe the superconducting temperature increase with pressure and then saturate beyond the critical pressure of the CDW at 4.8 GPa, indicating weak competition between superconductivity and charge order.