Emergence of charge density wave domain walls above the superconducting dome in 1T-TiSe2

Abstract

Superconductivity in so-called unconventional superconductors is nearly always found in the vicinity of another ordered state, such as antiferromagnetism, charge density wave (CDW), or stripe order. This suggests a fundamental connection between superconductivity and fluctuations in some other order parameter. To better understand this connection, we used high-pressure X-ray scattering to directly study the CDW order in the layered dichalcogenide TiSe2, which was previously shown to exhibit superconductivity when the CDW is suppressed by pressure1 or intercalation of Cu atoms2. We succeeded in suppressing the CDW fully to zero temperature, establishing for the first time the existence of a quantum critical point (QCP) at Pc = 5.1 ± 0.2 GPa, which is more than 1 GPa beyond the end of the superconducting region. Unexpectedly, at P = 3 GPa we observed a reentrant, weakly first order, incommensurate phase, indicating the presence of a Lifshitz tricritical point somewhere above the superconducting dome. Our study suggests that superconductivity in TiSe2 may not be connected to the QCP itself, but to the formation of CDW domain walls.

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Figure 1: Suppression of the charge density wave in 1T-TiSe2 with temperature and pressure.
Figure 2: Summary pressure–temperature phase diagram of TiSe2.
Figure 3: Precision measurement of the charge density wave commensurability in TiSe2 at two selected pressures, using the two-energy technique introduced in the text.

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Acknowledgements

We gratefully acknowledge discussions with P. B. Littlewood, M. R. Norman, R. Osborn and W-C. Lee. High-pressure X-ray experiments were supported by the US Department of Energy under grant No. DE-FG02-06ER46285. Crystal growth was supported by DOE grant No. DE-FG02-07ER46453. Use of the CHESS was supported by the National Science Foundation and the National Institutes of Health/National Institute of General Medical Sciences under NSF award DMR-0936384. T.C.C. was supported by DOE grant No. DE-FG02-07ER46383.

Author information

Y.I.J. and P.A. designed the experiment. Y.I.J., K.D.F. and P.A. built the experimental apparatus. Y.I.J., X.M.C., K.D.F., G.A.P., Y.G., J.C.T.L., J.G. and P.A. performed the X-ray experiments. S.Y., Y.I.J. and S.L.C. grew the crystals. Y.I.J., P.G., G.J.M., S.L.C., T.C.C., E.F. and P.A. analysed and interpreted the data. P.A. wrote the paper.

Correspondence to P. Abbamonte.

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Joe, Y., Chen, X., Ghaemi, P. et al. Emergence of charge density wave domain walls above the superconducting dome in 1T-TiSe2. Nature Phys 10, 421–425 (2014). https://doi.org/10.1038/nphys2935

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