Abstract
Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. A well recognized example is high-temperature superconductivity which cannot be understood in terms of the standard weak-coupling theory. The exotic properties that accompany the formation of the two-channel Kondo (2CK) effect, including the emergence of an unconventional metallic state in the low-energy limit, also originate from strong electron interactions. Despite its paradigmatic role for the formation of non-standard metal behavior, the stringent conditions required for its emergence have made the observation of the nonmagnetic, orbital 2CK effect in real quantum materials difficult, if not impossible. We report the observation of orbital one- and two-channel Kondo physics in the symmetry-enforced Dirac nodal line (DNL) metals IrO2 and RuO2 nanowires and show that the symmetries that enforce the existence of DNLs also promote the formation of nonmagnetic Kondo correlations. Rutile oxide nanostructures thus form a versatile quantum matter platform to engineer and explore intrinsic, interacting topological states of matter.
Highlights
Strong electron correlations have long been recognized as driving the emergence of novel phases of matter
For the sites M1 and M2, an almost perfect C4ν symmetry exists which implies a corresponding degeneracy associated with the two-dimensional irreducible representation of C4ν, see Fig. 1c and Supplementary Note 4
The π/2 angle between adjacent octahedra leads to a fourfold screw axis symmetry
Summary
Strong electron correlations have long been recognized as driving the emergence of novel phases of matter. One of the simplest routes to singular Fermi liquid behavior, at least conceptually, is through two-channel Kondo (2CK) physics[2,3,4] Despite this long-standing interest, 2CK physics has far only been demonstrated to arise in carefully designed semiconductor nanodevices in narrow energy and temperature (T) ranges[5,6,7,8], while claims of its observation in real quantum materials are contentious (see “Discussion” section for details). While there has been considerable progress in understanding weakly correlated topological metals, only a few materials have been identified as realizing topological phases driven by strong electron correlations, which includes the Weyl–Kondo semimetals[11] This raises the question if the 2CK counterpart of such a Weyl–Kondo semimetal, featuring an entangled ground state of the low-energy excitations of the 2CK effect with band-structure enforced Dirac or Weyl excitations, could at least in principle be stabilized. In this work we establish that oxygen vacancies (VO’s) in the
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