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Strong enhancement of superconductivity at high pressures within the charge-density-wave states of 2H−TaS2 and 2H−TaSe2

D. C. Freitas, P. Rodière, M. R. Osorio, E. Navarro-Moratalla, N. M. Nemes, V. G. Tissen, L. Cario, E. Coronado, M. García-Hernández, S. Vieira, M. Núñez-Regueiro, and H. Suderow
Phys. Rev. B 93, 184512 – Published 24 May 2016
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  • INTRODUCTION
  • EXPERIMENT
  • RESULTS
  • DISCUSSION AND CONCLUSIONS
  • ACKNOWLEDGMENTS
    • References

    Abstract

    We present measurements of the superconducting and charge-density-wave (CDW) critical temperatures (Tc and TCDW) as a function of pressure in the transition metal dichalchogenides 2H−TaSe2 and 2H−TaS2. Resistance and susceptibility measurements show that Tc increases from temperatures below 1 K up to 8.5 K at 9.5 GPa in 2H−TaS2 and 8.2 K at 23 GPa in 2H−TaSe2. We observe a kink in the pressure dependence of TCDW at about 4 GPa that we attribute to the lock-in transition from incommensurate CDW to commensurate CDW. Above this pressure, the commensurate TCDW slowly decreases, coexisting with superconductivity within our full pressure range.

    • Figure
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    • Received 21 October 2015
    • Revised 30 March 2016

    DOI:https://doi.org/10.1103/PhysRevB.93.184512

    ©2016 American Physical Society

    Authors & Affiliations

    D. C. Freitas1,2,3, P. Rodière1,2, M. R. Osorio4, E. Navarro-Moratalla5, N. M. Nemes6, V. G. Tissen4,7,*, L. Cario8, E. Coronado5, M. García-Hernández9,10, S. Vieira4,10, M. Núñez-Regueiro1,2,†, and H. Suderow4,10

    • 1Université Grenoble Alpes, Institut Néel, F-38000 Grenoble, France
    • 2CNRS, Institut Néel, F-38000 Grenoble, France
    • 3Centro Brasileiro de Pesquisas Físicas, Rua Dr. Xavier Sigaud, 150, Urca, Rio de Janeiro–RJ, Brazil
    • 4Laboratorio de Bajas Temperaturas, Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales Nicolás Cabrera, Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, E-28049 Madrid, Spain
    • 5Instituto de Ciencia Molecular (ICMol), Universidad de Valencia, Catedrático José Beltrán 2, E-46980 Paterna, Spain
    • 6GFMC, Departamento de Física Aplicada III, Universidad Complutense de Madrid, Campus Moncloa, E-28040 Madrid, Spain
    • 7Institute of Solid State Physics, Chernogolovka, 142432 Moscow Region, Russia
    • 8Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP 32229, F-44322 Nantes Cedex 03, France
    • 9Instituto de Ciencia de Materiales de Madrid-CSIC, Cantoblanco E-28049 Madrid, Spain
    • 10Unidad Asociada de Bajas Temperaturas y Altos Campos Magnéticos, UAM, CSIC, Madrid, Spain

    • *Deceased.
    • †Corresponding author: nunez@neel.cnrs.fr

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    Issue

    Vol. 93, Iss. 18 — 1 May 2016

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    • Figure 1
      Figure 1

      Upper panels: Susceptibility of 2H−TaSe2 (left panel) and 2H−TaS2 (right panel) as a function of temperature for several applied pressures (5.3, 8.1, 11.7, 16.7, and 19.4 GPa for 2H−TaSe2 and 3.1, 5.8, 7.9, 9.8, 14.8, and 17.1 GPa for 2H−TaS2). Susceptibility has been normalized to the value found at 10 K, and the low-temperature value has been modified to give zero. Lower panels: Resistance as a function of temperature for 2H−TaSe2 (left panel) and for 2H−TaS2 (right panel) for several applied pressures (from 7.5 to 15 by 1.5 GPa steps and then every GPa up to 19 GPa for 2H−TaSe2 and every GPa from 1 to 20 GPa for 2H−TaS2). The resistance has been normalized to its value at 10 K.

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    • Figure 2
      Figure 2

      Derivative of the resistance close to the CDW ordering temperature for respectively 2H−TaSe2 (left panel) and 2H−TaS2 (right panel) for different pressures [1, 2, 3, 4, 5, 6, 7.5, 9, 10.5, 12, 13.5, 15, 16, 17, 18, and 19 GPa (left) and every GPa from 1 to 17 GPa (right)]. Curves are shifted in the y axis for clarity. An arrow is used to mark the position where we take TCDW to give the pressure dependence discussed in Fig. 3

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    • Figure 3
      Figure 3

      Phase diagram of the superconducting transition obtained from susceptibility (blue solid circles), resistance (light blue lozenges), and of the CDW transition (red triangles). Solid triangles at low pressures have been obtained from Smith et al. [25]. Typical error bars are shown. Blue lines are guides to the eyes. Green dashed lines in the top panel are the positions of the CDW as found in previous works for 2H−TaSe2 [26, 28, 29]. Inset: Proposed phase diagram for both compounds. Black dashed lines are extrapolations of the low-pressure range data (see text).

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