Concepts relating magnetic interactions, intertwined electronic orders, and strongly correlated superconductivity

Abstract

Unconventional superconductivity (SC) is said to occur when Cooper pair formation is dominated by repulsive electron-electron interactions, so that the symmetry of the pair wave function is other than an isotropic s-wave. The strong, on-site, repulsive electron-electron interactions that are the proximate cause of such SC are more typically drivers of commensurate magnetism. Indeed, it is the suppression of commensurate antiferromagnetism (AF) that usually allows this type of unconventional superconductivity to emerge. Importantly, however, intervening between these AF and SC phases, intertwined electronic ordered phases (IP) of an unexpected nature are frequently discovered. For this reason, it has been extremely difficult to distinguish the microscopic essence of the correlated superconductivity from the often spectacular phenomenology of the IPs. Here we introduce a model conceptual framework within which to understand the relationship between AF electronelectron interactions, IPs, and correlated SC. We demonstrate its effectiveness in simultaneously explaining the consequences of AF interactions for the copper-based, iron-based, and heavy-fermion superconductors, as well as for their quite distinct IPs.high-Tc superconductivity | strong correlations | fermiology E mergence, the coming into being through evolution, is an important concept in modern condensed matter physics (1). Superconductivity is a classic example of emergence in the realm of quantum matter: as the energy scale decreases, the effective electron-electron interactions responsible for Cooper pairing and thus superconductivity evolves from the elementary microscopic Hamiltonian through unanticipated modifications (2). This evolution is why it is so difficult to derive superconductivity (SC) from first principles. Finding the microscopic mechanism of Cooper pairing means discovering the nature of the ultimate effective electron-electron interaction at the lowest energy scales.In the last three decades, unconventional (3-5) forms of SC have been discovered in many strongly correlated (repulsive electronelectron interaction) systems. These materials fascinate a lay person for their high superconducting transition temperatures and therefore the potential for revolutionary applications in power generation/transmission, transport, information technology, science, and medicine. They intrigue (and challenge) physicists to identify the mechanism of their high pairing-energy scale and because of the many intertwined (6, 7) electronic phases (IPs) that have been discovered in juxtaposition with the unconventional superconductivity. These IPs have been hypothesized to "arise together from one parent state" such that "the various order parameters are intertwined rather than simply competing with each other" (7). The best known and most widely studied examples of such materials include the copper-based (8-11) and ironbased (12-14) high-temperature superconductors, the heavy fermion superconductors (15)(16)(17), and the organic superconductors (18). One thing...

Amperean Pairing and the Pseudogap Phase of Cuprate Superconductors

“…With the discovery of CDW order, it seems natural to associate the energy gap induced by CDW with the pseudogap [50][51][52][53]. Here, we show that a mean-field picture of the CDW fails to explain the ARPES data of He et al [12].…”

“…We note that Ref. [53] assumes an interference between the CDWs in the x and y directions, so the gap vanishes at the "hot spot." However, the gap reopens away from the hot spot and should be visible below the Fermi level in the Fermi arc region.…”

Temperature Dependence of the Electronic Structure of FeSe

“…Площа електронних та дірко-вих кишень зменшується або збільшується таким чином, що пов-ний заряд залишається постійним. При підвищенні температури в межах моделів, що пояснюють такий зсув як результат взаємодії з бозонною модою, поверхня Ôермі мала б наближатися до розрахо-ваної [15,16].…”

Atomic-scale electronic structure of the cuprate d-symmetry form factor density wave state

“…This is relevant to the high-temperature superconducting cuprates because numerous researchers have recently proposed that the 'pseudogap' regime 1,2 (PG in Fig. 1a) contains an unconventional density wave with a d-symmetry form factor [17][18][19][20][21][22][23][24][25][26][27][28][29] . The basic phenomenology of such a state is that intraunit-cell (IUC) symmetry breaking renders the O x and O y sites within each CuO 2 unit-cell electronically inequivalent, and that this inequivalence is then modulated periodically at wavevector Q parallel to (1,0);(0,1).…”

“…Such a state is then described by A(r) = D(r) cos(φ(r) + φ 0 (r)), where A(r) represents whatever is the modulating electronic degree of freedom, φ(r) = Q x · r is the DW spatial phase at location r, φ 0 (r) represents disorder related spatial phase shifts, and D(r) is the magnitude of the d-symmetry form factor 14,21,23 . To distinguish between the various microscopic mechanisms proposed for the Q = (Q, 0); (0, Q) dFF-DW state of cuprates [17][18][19][20][21][22][23][24][25][26][27][28][29] , it is essential to establish its atomic-scale phenomenology, including the momentum space (k-space) eigenstates contributing to its spectral weight, the relationship (if any) between modulations occurring above and below the Fermi energy, whether the modulating states in the DW are associated with a characteristic energy gap, and how the dFF-DW evolves with doping.To visualize such phenomena directly as in Fig. 1c, we use sublattice-phase-resolved imaging of the electronic structure 14 of the CuO 2 plane.…”