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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Kusmartseva, A. F., Sipos, B., Berger, H., Forró, L. & Tutiš, E. Pressure induced superconductivity in 1T-TiSe2 . Phys. Rev. Lett. 103, 236401 (2009).
Morosan, E. et al. Superconductivity in CuxTiSe2 . Nature Phys. 2, 544–550 (2006).
Mathur, N. D. et al. Magnetically mediated superconductivity in heavy fermion compounds. Nature 394, 39–43 (1998).
Canfield, P. C. & Bud’ko, S. L. FeAs-based superconductivity: A case study of the effects of transition metal doping on BaFe2As2 . Ann. Rev. Cond. Matter Phys. 1, 27–50 (2010).
Nakatsuji, S. & Maeno, Y. Quasi-two-dimensional Mott transition system Ca2 − xSrxRuO4 . Phys. Rev. Lett. 84, 2666–2669 (2000).
Tranquada, J. M., Sternlieb, B. J., Axe, J. D., Nakamura, Y. & Uchida, S. Evidence for stripe correlations of spins and holes in copper-oxide superconductors. Nature 375, 561–563 (1995).
Rossnagel, K. On the origin of charge density waves in select layered transition-metal dichalcogenides. J. Phys. Condens. Matter 23, 213001 (2011).
DiSalvo, F. J., Moncton, D. E. & Waszczak, J. V. Electronic properties and superlattice formation in the semimetal TiSe2 . Phys. Rev. B 14, 4321–4328 (1976).
Barath, H. et al. Quantum and classical mode softening near the charge-density-wave/superconductor transition of CuxTiSe2 . Phys. Rev. Lett. 100, 106402 (2008).
Snow, C. S., Karpus, J. F., Cooper, S. L., Kidd, T. E. & Chiang, T-C. Quantum melting of the charge-density-wave state in 1T-TiSe2 . Phys. Rev. Lett. 91, 136402 (2003).
May, M. M., Brabetz, C., Janowitz, C. & Manzke, R. Charge-density-wave phase of 1T-TiSe2: The influence of conduction band population. Phys. Rev. Lett. 107, 176405 (2011).
Kidd, T. E., Miller, T., Chou, M. Y. & Chiang, T-C. Electron–hole coupling and the charge density wave transition in TiSe2 . Phys. Rev. Lett. 88, 226402 (2002).
Van Wezel, J., Nahai-Williamson, P. & Saxena, S. S. Exciton-phonon-driven charge density wave in TiSe2 . Phys. Rev B 81, 165109 (2010).
Monney, C., Battaglia, C., Cercellier, H., Aebi, P. & Beck, H. Exciton condensation driving the periodic lattice distortion of 1T-TiSe2 . Phys. Rev. Lett. 106, 106404 (2011).
Hellmann, S. et al. Time-domain classification of charge-density-wave insulators. Nature Commun. 3, 1039 (2012).
Castellan, J-P. et al. Chiral phase transition in charge-ordered 1T-TiSe2 . Phys. Rev. Lett. 110, 196404 (2013).
Weber, F. et al. Electron–phonon coupling and the soft phonon mode in TiSe2 . Phys. Rev. Lett. 107, 266401 (2011).
Abbamonte, P. et al. Ultrafast imaging and the phase problem for inelastic X-ray scattering. Adv. Mater. 22, 1141–1147 (2010).
Holt, M., Zschack, P., Hong, H., Chou, M. Y. & Chiang, T-C. X-ray studies of phonon softening in TiSe2 . Phys. Rev. Lett. 86, 3799–3802 (2001).
Hertz, J. A. Quantum critical phenomena. Phys. Rev. B 14, 1165–1184 (1976).
Millis, A. J. Effect of nonzero temperature on quantum critical points in itinerant fermion systems. Phys. Rev. B 48, 7183–7196 (1993).
McMillan, W. L. Microscopic model of charge-density waves in 2H-TaSe2 . Phys. Rev. B 16, 643–650 (1977).
Calandra, M. & Mauri, F. Charge-density wave and superconducting dome in TiSe2 from electron–phonon interaction. Phys. Rev. Lett. 106, 196406 (2011).
Hornreich, R. M. The Lifshitz point: Phase diagrams and critical behavior. J. Magn. Magn. Mater. 15-18, 387–392 (1980).
Moncton, D. E., Axe, J. D. & DiSalvo, F. J. Study of superlattice formation in 2H-NbSe2 and 2H-TaSe2 by neutron scattering. Phys. Rev. Lett. 34, 734 (1975).
Sipos, B. et al. From Mott state to superconductivity in 1T-TaS2 . Nature Mater. 7, 960–965 (2008).
Fradkin, E. & Kivelson, S. A. High-temperature superconductivity: Ineluctable complexity. Nature Phys. 8, 864–866 (2012).
Mesaros, A. et al. Topological defects coupling smectic modulations to intra-unit-cell nematicity in cuprates. Science 333, 426–430 (2011).
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.
The authors declare no competing financial interests.
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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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