Superconductivity under Pressure in(U1−xThx)

Abstract

The inAuence of pressure P on the superconducting transition temperature T, has been determined for the {Ui "Th")Bei3 system. The magnitude of dT, /dP increases by a factor of 3 for x ) 1.7'/o where an increase of T, is observed at ambient pressure. The phase diagram of T, {x)for I' = 10 kbar shows two distinct regions of superconductivity.

Pressure tuning of the double transition in thoriatedUBe13

“…Earlier susceptibility [12] and thermal expansion [18] measurements have conflicting implications for dT, 2/dP. Our dT, /dP values agree roughly with the susceptibility studies on samples with x-0.02, taken over a larger pressure range but with a coarser grid [12] (dT, 2/dP is not, of course, directly accessible in a susceptibility measurement).…”

“…6 mg; in order to achieve higher pressures we later spark cut the sample to 3 [12]. We find that dT, /dP varies from -29~5 mK/kbar at low pressures (P =0.5 kbar) to -100~10 mK/kbar approaching P, =2.1 kbar.…”

“…1 We apply uniaxial stress at room temperature with a superconducting NbTi cell [13]. We apply uniaxial rather than hydrostatic pressure in order to avoid a large background heat capacity from the pressure cell and because we are able to make controlled adjustments in pressure at intervals an order of magnitude smaller than those reported in previous measurements on (U,Th)Be}3 [12,14]. Our minimum step size of 0.1 kbar corresponds to a change in x of less than 0.0002 [Eq.…”

Heavy fermion superconductivity: 5f vs 4f

“…Further, when magnetic field is applied, the second superconducting region completely separates from the first, appearing very much like the schematic phase diagram in Fig. 8 [17]. However, that the second dome is coming from valence fluctuations seems unlikely, given the small variation in entropy recovered by T C in the various alloys.…”

Evidence for unconventional superconductivity in single crystals of the antiferromagnetic heavy-electron compound URu2Si2

“…One of the most striking recent developments is the apparent occurrence of two or more distinct superconducting phases in (U 1 _Th,)Be 13 as a function of Th composition x [20] as revealed by high-pressure experiments [21] and in UPt, in the H-T plane . The case of UPt, has been studied extensively and is the subject of several theoretical investigations in which the multiple superconducting transitions have been attributed to coupled antiferromagnetic and multicomponent superconducting order parameters [25,261.…”