Coexistence of local magnetism and superconductivity in the heavy-fermion compound <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>CeRh</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>As</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> revealed by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>μ</mml:mi> <mml:mi>SR</mml:mi> </mml:mrow> </mml:math> studies
Seunghyun Khim, O. Stockert, M. Brando, C. Geibel, C. Baines, T. J. Hicken, H. Luetkens, Debarchan Das, T. Shiroka, Zurab Guguchia, R. Scheuermann
Abstract
The superconducting (SC) state ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:mrow> <a:msub> <a:mi>T</a:mi> <a:mi mathvariant="normal">c</a:mi> </a:msub> <a:mo>=</a:mo> <a:mn>0.3</a:mn> <a:mspace width="0.28em"/> <a:mi mathvariant="normal">K</a:mi> </a:mrow> </a:math> ) of the heavy-fermion compound <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:mrow> <e:msub> <e:mi>CeRh</e:mi> <e:mn>2</e:mn> </e:msub> <e:msub> <e:mi>As</e:mi> <e:mn>2</e:mn> </e:msub> </e:mrow> </e:math> , which undergoes an unusual field-induced transition to another high-field SC state, emerges from an unknown ordered state below <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:msub> <f:mi>T</f:mi> <f:mi mathvariant="normal">o</f:mi> </f:msub> <f:mo>=</f:mo> <f:mn>0.55</f:mn> <f:mspace width="0.28em"/> <f:mi mathvariant="normal">K</f:mi> </f:mrow> </f:math> . While an electronic multipolar order of itinerant <j:math xmlns:j="http://www.w3.org/1998/Math/MathML"> <j:mrow> <j:mi>Ce</j:mi> <j:mtext>−</j:mtext> <j:mn>4</j:mn> <j:mi>f</j:mi> </j:mrow> </j:math> states was proposed to account for the <k:math xmlns:k="http://www.w3.org/1998/Math/MathML"> <k:msub> <k:mi>T</k:mi> <k:mi mathvariant="normal">o</k:mi> </k:msub> </k:math> phase, the exact order parameter has not been known to date. Here, we report on muon spin relaxation ( <m:math xmlns:m="http://www.w3.org/1998/Math/MathML"> <m:mrow> <m:mi>μ</m:mi> <m:mi>SR</m:mi> </m:mrow> </m:math> ) studies of the magnetic and SC properties in <n:math xmlns:n="http://www.w3.org/1998/Math/MathML"> <n:mrow> <n:msub> <n:mi>CeRh</n:mi> <n:mn>2</n:mn> </n:msub> <n:msub> <n:mi>As</n:mi> <n:mn>2</n:mn> </n:msub> </n:mrow> </n:math> single crystals at low temperatures. We reveal a magnetic origin of the <o:math xmlns:o="http://www.w3.org/1998/Math/MathML"> <o:msub> <o:mi>T</o:mi> <o:mi mathvariant="normal">o</o:mi> </o:msub> </o:math> order by identifying a spontaneous internal field below <q:math xmlns:q="http://www.w3.org/1998/Math/MathML"> <q:mrow> <q:msub> <q:mi>T</q:mi> <q:mi mathvariant="normal">o</q:mi> </q:msub> <q:mo>=</q:mo> <q:mn>0.55</q:mn> <q:mspace width="0.28em"/> <q:mi mathvariant="normal">K</q:mi> </q:mrow> </q:math> . Furthermore, we find evidence of a microscopic coexistence of local magnetism with bulk superconductivity. Our results suggest the possibility that the <u:math xmlns:u="http://www.w3.org/1998/Math/MathML"> <u:msub> <u:mi>T</u:mi> <u:mi mathvariant="normal">o</u:mi> </u:msub> </u:math> phase involves both dipole and higher-order <w:math xmlns:w="http://www.w3.org/1998/Math/MathML"> <w:mrow> <w:mi>Ce</w:mi> <w:mtext>−</w:mtext> <w:mn>4</w:mn> <w:mi>f</w:mi> </w:mrow> </w:math> moments to account for the unusual shape of the <x:math xmlns:x="http://www.w3.org/1998/Math/MathML"> <x:mrow> <x:msub> <x:mi>T</x:mi> <x:mi mathvariant="normal">o</x:mi> </x:msub> <x:mrow> <x:mo>(</x:mo> <x:mi>B</x:mi> <x:mo>)</x:mo> </x:mrow> </x:mrow> </x:math> phase boundary.