Visualizing heavy fermion confinement and Pauli-limited superconductivity in layered CeCoIn5

Abstract

Layered material structures play a key role in enhancing electron–electron interactions to create correlated metallic phases that can transform into unconventional superconducting states. The quasi-two-dimensional electronic properties of such compounds are often inferred indirectly through examination of bulk properties. Here we use scanning tunneling microscopy to directly probe in cross-section the quasi-two-dimensional electronic states of the heavy fermion superconductor CeCoIn5. Our measurements reveal the strong confined nature of quasiparticles, anisotropy of tunneling characteristics, and layer-by-layer modulated behavior of the precursor pseudogap gap phase. In the interlayer coupled superconducting state, the orientation of line defects relative to the d-wave order parameter determines whether in-gap states form due to scattering. Spectroscopic imaging of the anisotropic magnetic vortex cores directly characterizes the short interlayer superconducting coherence length and shows an electronic phase separation near the upper critical in-plane magnetic field, consistent with a Pauli-limited first-order phase transition into a pseudogap phase.

Microscopic theory of pseudogap phenomena and unconventional Bose-liquid superconductivity and superfluidity in high-$T_c$ cuprates and other systems

“…By taking E p = 0.04 eV and ω 0 0.018 eV for this system, we find T * 50 K at λ * p = 0.354 in accordance with the above experimental results [186]. Experimental data show [17,18,[193][194][195] that the heavy-fermion superconductors UPd 2 Al 3 , YbAl 3 and CeCoIn 5 , which have many similarities to the high-T c cuprates, also have a pseudogap state above T c . The common feature of these compounds is that they contain f electrons having localized orbitals and characterized by the narrow f electron bands, so that the effective masses of charge carriers are very large m * 50 − 200m e [18].…”

“…The theory developed to explain the pseudogap behavior of high-T c cuprates may be also applicable to heavyfermion superconductors which exhibit a similar behavior in many regards [17,29]. In particular, there are signatures of quasiparticle confinement in the normal state of the heavy-fermion superconductor CeCoIn 5 [195]. The electronic structure of heavy-fermion systems can be described by the nearly localized narrow f band that cause the heavy-fermion behavior and the itinerant f − c hybridized band [199] which is a relatively broad to support superconductivity.…”

Coexistence of Quasi-two-dimensional Superconductivity and Tunable Kondo Lattice in a van der Waals Superconductor

“…[8,13,31] We also believe that the 1T-TaS2-related superconducting materials may provide a new platform for exploring the interplay between Kondo resonance and superconductivity, which would be helpful for further understanding the heavy fermion superconductivity. [30,[32][33][34][35]…”

Strong Rashba Effect and Different f−d Hybridization Phenomena at the Surface of the Heavy‐Fermion Superconductor CeIrIn5

“…The electronic structure and magnetic interactions in strongly correlated f materials have traditionally attracted considerable attention due to their rich and unusual physical properties, where not only the bulk phenomena are investigated, but also the surfaces, interfaces, and multilayers of such systems become the subject of research efforts. [1][2][3][4][5] Recent photoemission insights into the electronic and magnetic properties of silicide-and rare-earth-terminated surfaces of strongly correlated electron materials of the RET 2 Si 2 family (RE and T are rare-earth and transition-metal atoms, correspondingly) have unveiled novel temperature scales linked with the Kondo interaction, heavy-fermion behavior, mixed-valent properties, and exchange magnetism that are remarkably different to those in the bulk. [6][7][8][9][10][11][12][13][14] Essentially, these studies illustrate that the surfaces of strongly correlated materials with a quasi-2D structure can be viewed as versatile platforms for unveiling novel f-driven phenomena and disentangling the different surface and bulk contributions to the aforementioned many-body effects.…”