Emergence of Superconductivity on the Border of Antiferromagnetic Order in RbMn<sub>6</sub>Bi<sub>5</sub> under High Pressure: A New Family of Mn-Based Superconductors
Pengtao Yang, Qingxin Dong, Pengfei Shan, Ziyi Liu, Jianping Sun, Zhiling Dun, Yoshiya Uwatoko, Genfu Chen, Bosen Wang, Jinguang Cheng
Abstract
We report the discovery of superconductivity on the border of antiferromagnetic order in a quasi-one-dimensional material RbMn 6 Bi 5 via measurements of resistivity and magnetic susceptibility under high pressures. Its phase diagram of temperature versus pressure resembles those of many magnetism-mediated superconducting systems. With increasing pressure, its antiferromagnetic ordering transition with T N = 83 K at ambient pressure is first enhanced moderately and then suppressed completely at a critical pressure of P c ≈ 13 GPa, around which bulk superconductivity emerges and exhibits a dome-like T c ( P ) with a maximal <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mi mathvariant="normal">c</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">onset</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≈</mml:mo> <mml:mn>9.5</mml:mn> </mml:mrow> </mml:math> K at about 15 GPa. In addition, the superconducting state around P c is characterized by a large upper critical field μ 0 H c2 (0) exceeding the Pauli paramagnetic limit, implying a possible unconventional paring mechanism. The present study, together with our recent work on KMn 6 Bi 5 (the maximum <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>T</mml:mi> <mml:mi mathvariant="normal">c</mml:mi> <mml:mrow> <mml:mi mathvariant="normal">onset</mml:mi> </mml:mrow> </mml:msubsup> <mml:mo>≈</mml:mo> <mml:mn>9.3</mml:mn> </mml:mrow> </mml:math> K), makes A Mn 6 Bi 5 ( A = alkali metal) a new family of Mn-based superconductors with relatively high T c .