Enhancement and reentrance of spin triplet superconductivity in ${\mathrm{UTe}}_{2}$ under pressure

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Enhancement and reentrance of spin triplet superconductivity in ${UTe}_{2}$ under pressure

Sheng Ran, Hyunsoo Kim, I-Lin Liu, Shanta R. Saha, Ian Hayes, Tristin Metz, Yun Suk Eo, Johnpierre Paglione, and Nicholas P. Butch

Phys. Rev. B 101, 140503(R) – Published 14 April 2020

Abstract

Spin triplet superconductivity in the Kondo lattice ${UTe}_{2}$ appears to be associated with spin fluctuations originating from incipient ferromagnetic order. Here we show clear evidence of twofold enhancement of superconductivity under pressure, which discontinuously transitions to magnetic order, likely of ferromagnetic nature, at higher pressures. The application of a magnetic field tunes the system back across a first-order phase boundary. Straddling this phase boundary, we find another example of reentrant superconductivity in ${UTe}_{2}$ . As the superconductivity and magnetism exist on two opposite sides of the first-order phase boundary, our results indicate other microscopic mechanisms may be playing a role in stabilizing spin triplet superconductivity in addition to spin fluctuations associated with magnetism.

Received 29 September 2019
Revised 16 March 2020
Accepted 19 March 2020

DOI:https://doi.org/10.1103/PhysRevB.101.140503

Physics Subject Headings (PhySH)

Kondo effect Spin-triplet pairing Superconductivity

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Sheng Ran ^1,2,3, Hyunsoo Kim¹, I-Lin Liu ^1,2,3, Shanta R. Saha^1,2, Ian Hayes¹, Tristin Metz¹, Yun Suk Eo¹, Johnpierre Paglione^1,2, and Nicholas P. Butch^1,2

¹Quantum Materials Center, Department of Physics, University of Maryland, College Park, Maryland 20742, USA
²NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
³Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA

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Vol. 101, Iss. 14 — 1 April 2020

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Figure 1
Phase diagram of ${UTe}_{2}$ under pressure in zero magnetic field. (a) Color contour plot of the resistivity data as a function of both temperature and pressures in zero magnetic field, and the resulting phase diagram. Solid red dots represent the $T_{c}$ of superconductivity determined from resistance measurements. Error bars are defined by the onset and offset of superconducting transition. The half open red dots represent the $T_{c}$ of superconductivity determined from magnetization measurements. Brown dots represent the kinks in the $R (T)$ data in the low-pressure range. Blue and green dots represent the local minimums in the $R (T)$ data in the high-pressure range. The gray region indicates the critical pressure region of finite width. Note that for 1.4 GPa, the resistance shows a dramatic drop without reaching zero. Superconductivity reenters in the magnetic field. (b) The temperature dependence of resistivity data in zero magnetic field for selected pressure values. The low-temperature resistivity exhibits a clear evolution in slope, from positive to negative, as pressure increases.
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Figure 2
Magnetic field as a tuning parameter. (a),(b) Resistance data as a function of temperature for different magnetic fields, for 1.18 and 1.4 GPa. Negative normal-state magnetoresistance and sharp upper critical fields are evident. (c),(d) Resistance data as a function of magnetic field for different temperatures, for 1.18 and 1.4 GPa. Reentrant SC is readily apparent in the low-temperature magnetoresistance.
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Figure 3
Hysteresis in temperature and magnetic field for 1.4 GPa. (a) Magnetic and superconducting phase boundaries at 1.4 GPa. In the pink region hysteresis is observed in the temperature-dependent resistance data. In the gray region, superconductivity coexists with magnetism, and hysteresis is observed in the field-dependent resistance data. Error bars of $T_{c}$ are defined by the onset and offset of superconducting transition. (b) Resistance data as a function of temperature for $H = 0$ and 6 T, showing clear hysteresis in temperature when the magnetic phase is suppressed to low enough temperature. (c) Resistance data as a function of magnetic field from $- 1$ to 1 T for 0.3, 1, 2, and 3 K, showing hysteresis in magnetic field in the region where superconductivity coexists with magnetism.
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Figure 4
Schematic phase diagram of ${UTe}_{2}$ , emphasizing the opposing roles of pressure $P$ and magnetic field $H$ as tuning parameters. For clarity, only one of the phase transitions in the high-pressure region is plotted. In the low-pressure region, paramagnetic superconductivity ${SC}_{PM}$ (in yellow) exists below $T^{*}$ . On the high-pressure side of the critical pressure $P_{c}$ , magnetic order (green) is suppressed by field, and reentrant superconductivity ${SC}_{FM}$ is observed at low temperature (blue). Coexistence of magnetism and SC is observed at these pressures. Constant pressure slices are shown for low pressure (i), 1.35 GPa (ii), and 1.4 GPa (iii). In (i), the $T$ and $H$ limits of superconductivity are rather pressure insensitive. In (ii) and (iii), the magnetism/SC coexistence regions are marked in gray, and the relationship between optimal SC and suppression of magnetism are clearly seen. Error bars of $T_{c}$ are defined by the onset and offset of superconducting transition.
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Physical Review B

covering condensed matter and materials physics

Enhancement and reentrance of spin triplet superconductivity in ${UTe}_{2}$ under pressure

Sheng Ran, Hyunsoo Kim, I-Lin Liu, Shanta R. Saha, Ian Hayes, Tristin Metz, Yun Suk Eo, Johnpierre Paglione, and Nicholas P. Butch

Phys. Rev. B 101, 140503(R) – Published 14 April 2020

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Physical Review B

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Enhancement and reentrance of spin triplet superconductivity in UTe2 under pressure

Sheng Ran, Hyunsoo Kim, I-Lin Liu, Shanta R. Saha, Ian Hayes, Tristin Metz, Yun Suk Eo, Johnpierre Paglione, and Nicholas P. Butch

Phys. Rev. B 101, 140503(R) – Published 14 April 2020

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Enhancement and reentrance of spin triplet superconductivity in ${UTe}_{2}$ under pressure