How ground states of quantum matter transform between one another reveals deep insights into the mechanisms stabilizing them. Correspondingly, quantum phase transitions are explored in numerous materials classes, with heavy fermion compounds being among the most prominent ones. Recent studies in an anisotropic heavy fermion compound have shown that different types of transitions are induced by variations of chemical or external pressure 1-3 , raising the question of the extent to which heavy fermion quantum criticality is universal.To make progress, it is essential to broaden both the materials basis and the microscopic parameter variety. Here, we identify a cubic heavy fermion material as exhibiting a field-induced quantum phase transition, and show how the material can be used to explore one extreme of the dimensionality axis. The transition between two different ordered phases is accompanied by an abrupt change of Fermi surface, reminiscent of what happens across the field-induced antiferromagnetic to paramagnetic transition in the anisotropic YbRh 2 Si 2 . This finding leads to a materials-based global phase diagram -a precondition for a unified theoretical description.1 Quantum phase transitions arise in matter at zero temperature due to competing interactions. When they are continuous, the associated quantum critical points (QCPs) give rise to collective excitations which influence the physical properties over a wide range of parameters. As such, they are being explored in a variety of electronic materials, ranging from high T c cuprates to insulating magnets and quantum Hall systems 4,5 .Heavy fermion compounds are prototype materials to study quantum phase transitions. Their low energy scales allow to induce such transitions deliberately, by the variation of external parameters such as pressure or magnetic field. Microscopically, electrons in partiallyfilled f shells behave as localized magnetic moments. They interact with conduction electrons through a Kondo exchange interaction, which favors a non-magnetic ground state that entangles the local moments and the spins of the conduction electrons. They also interact among themselves through an RKKY exchange interaction, which typically induces antiferromagnetic order. It has been known that tuning external parameters changes the ratio of the Kondo coupling to the RKKY interaction. Recently, the importance of a second microscopic quantity has been suggested. This is the degree of quantum fluctuations of the local moments, parameterized by G: magnetic order weakens with increasing G, as it would with enhancing the Kondo coupling J K . These two quantities define a two-dimensional parameter space, which allows the consideration of a global phase diagram 10 . This global phase diagram is most clearly specified via the energy scale T * associated with the breakdown of the Kondo entanglement between the local moments and conduction electrons. So far T * has only been identified in tetragonal YbRh 2 Si 2 (refs. 8,11,12 ). It is believed that this energy scale no...

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Ice-rule breaking spin-flip in a pyrochlore spin ice compound Dy 2 Ti 2 O 7 has been studied in a field applied near the [112] direction, by means of angle-resolved magnetization measurements. We obtained strong evidence that the magnetization component perpendicular to the ( 11 1) kagomé plane undergoes a first-order transition below ∼0.26 K. This transition is driven by a ferromagnetic ordering in the field-decoupled spins on the triangular lattice in Dy 2 Ti 2 O 7 , as predicted theoretically.

Ice-rule breaking spin flip in the pyrochlore spin-ice compound Dy2Ti2O7 has been studied in a field rotated in the plane, by means of angle-resolved magnetization measurements. The field-angle dependence of the spin flip field Hc(θ) has been obtained. Close to the [111] direction, Hc(θ) exhibits a marked deviation from a nearest-neighbour spin-ice model, suggesting the importance of long-range dipolar interaction and a stability of the kagomé ice state.