Abstract
The heavy-fermion metal YbRh$_2$Si$_2$ realizes a field-induced quantum critical point with multiple vanishing energy scales $T_{\rm N}(B)$ and $T^\ast(B)$. We investigate their change with partial non-isoelectronic substitutions, chemical and hydrostatic pressure. Low-temperature electrical resistivity, specific heat and magnetic susceptibility of Yb(Rh$_{1-x}$T$_x$)$_2$Si$_2$ with T=Fe or Ni for $x\leq 0.1$, magnetic fields $B\leq 0.3$~T (applied perpendicular to the c-axis) and hydrostatic pressure $p\leq 1.5$~GPa are reported. The data allow to disentangle the combined influences of hydrostatic and chemical pressure, as well as non-isoelectronic substitution. In contrast to Ni- and Co-substitution, which enhance magnetic order, Fe-substitution acts oppositely. For $x=0.1$ it also completely suppresses the $T^\ast$ crossover and eliminates ferromagnetic fluctuations. The pressure, magnetic field and temperature dependences of $T^\ast$ are incompatible with its interpretation as Kondo breakdown signature.
Highlights
Rapid CommunicationsTuning low-energy scales in YbRh2Si2 by non-isoelectronic substitution and pressure. M.-H
Quantum phase transitions are of central importance in correlated materials
The heavy-fermion metal YbRh2Si2 realizes a field-induced quantum critical point with multiple vanishing energy scales TN(B) and T ∗(B). We investigate their change with partial non-isoelectronic substitutions, chemical and hydrostatic pressure
Summary
Tuning low-energy scales in YbRh2Si2 by non-isoelectronic substitution and pressure. M.-H. The heavy-fermion metal YbRh2Si2 realizes a field-induced quantum critical point with multiple vanishing energy scales TN(B) and T ∗(B). We investigate their change with partial non-isoelectronic substitutions, chemical and hydrostatic pressure. Whether well-defined quasiparticles exist at a quantum critical point (QCP) is relevant for understanding cuprates and heavy-fermion metals [1,2] The latter consist of lattices of certain f electrons and realize quantum criticality arising from two competing interactions: the indirect exchange coupling (RKKY interaction) between the f electrons, mediated by conduction electrons, and the Kondo screening acting on each f moment site. AF quantum criticality [13]
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