- Jun Gouchi: Pressure effect on the complex phase diagram of heavy-fermion superconductor UPt3
- 28. 8. 2019, 14:00
- lecture room F2, first floor Ke Karlovu 5
- more information
Abstract:
The heavy-fermion superconductor UPt3 is one of the famous unconventional superconductors. It is known to be in an odd-parity pairing state, which has a complex field - temperature phase diagram [1]. Two favorable candidates: pairing function E2u [2] and E1u scenarios [3] have been proposed. These scenarios are still controversial.
Josephson effect is very sensitive to the phase and spin state of the order parameter. For example, anisotropic temperature dependence of Josephson critical current have been observed at the transition from A to B of superconducting phase [4]. Whether superconducting state is a time-reversal symmetry breaking (TRSB) which can be clarified from field dependence of measurements.
In our researches, superconducting states of UPt3 is not BTRS [5]. The superconducting state at ambient pressure can be explained by E1u scenario. In the tri-critical point of UPt3 under pressure, the Meissner fraction at 0.2 K reaches a minimum value at . and the penetration depth decrease. These results suggest that the superconducting phase is modified above .[6].
Recent development of the ISSP high-pressure labs about two-stage multi anvil apparatus generating pressure over 20 GPa and specially designed the clamp type Palm CAC working down to 10 mK and magnetic field 9 T will be introduced.
[1] G. Bruls et al. Phys. Rev. Lett. 65 2294 (1990).
[2] J. A. Sauls J. Low Temp. Phys. 95, 153 (1994).
[3] Y. Machida et al. Phys. Rev. Lett. 108, 157002 (2012).
[4] A. Sumiyama et al. Phys. Rev. Lett. 81, 5213 (1998).
[5] J. Gouchi et al. J. Phys. Soc. Jpn. 81, 113701 (2012).
[6] J. Gouchi et al. Phys. Rev. B 93, 174514 (2016).
Figure. (a) Magnetic field modulation of for the c-axis junction. The solid line indicates fit using the Fraunhofer diffraction pattern. (b)Pressure dependence of Meissner fraction and superconducting transition temperature .