Fermionic order by disorder in a van der Waals antiferromagnet

Abstract

CeTe3 is a unique platform to investigate the itinerant magnetism in a van der Waals (vdW) coupled metal. Despite chemical pressure being a promising route to boost quantum fluctuation in this system, a systematic study on the chemical pressure effect on Ce3+(4f1) states is absent. Here, we report on the successful growth of a series of Se doped single crystals of CeTe3. We found a fluctuation driven exotic magnetic rotation from the usual easy-axis ordering to an unusual hard-axis ordering. Unlike in localized magnetic systems, near-critical magnetism can increase itinerancy hand-in-hand with enhancing fluctuation of magnetism. Thus, seemingly unstable hard-axis ordering emerges through kinetic energy gain, with the self-consistent observation of enhanced magnetic fluctuation (disorder). As far as we recognize, this order-by-disorder process in fermionic system is observed for the first time within vdW materials. Our finding opens a unique experimental platform for direct visualization of the rich quasiparticle Fermi surface deformation associated with the Fermionic order-by-disorder process. Also, the search for emergent exotic phases by further tuning of quantum fluctuation is suggested as a promising future challenge.

Magnetic frustration in a van der Waals metal CeSiI

“…An essential component to accelerate the development of the field is to increase the number of materials that host states whose properties are described by multiple coupled degrees of freedom, such as charge, spin, orbital, and lattice [5]. Among these, a particularly interesting playground for discovering phenomena like these has been identified in systems which manifest an interplay between itinerant electrons and magnetism, and intensive studies have been pursued and reported [6][7][8][9][10][11][12][13][14][15][16][17]. However, a promising area of this playground which simultaneously remains relatively unexplored is that of vdW materials, where itinerant electrons coexist with low-dimensional and potentially frustrated magnetism.…”

Electron quasi-itinerancy intertwined with quantum order by disorder in pyrochlore iridate magnetism

“…64 In the doped maganites, to gain the kinetic energy, the local moments twist themselves from the spin configuration favored by the exchange energy. Another possibly electron kinetic energy driven magnetism was proposed for the doped van der Waals antiferromagnet CeTe 3 , 65 and was refereed as fermionic order by disorder. For our case here, the electron kinetic energy is optimized within the background of the magnetism that operates on the continuously degenerate manifold.…”

Atomic-scale visualization of a cascade of magnetic orders in the layered antiferromagnet GdTe3

“…This class of van der Waals materials hosts an interesting unidirectional incommensurate charge density wave state with magnitude jq cdw j≈ 2 7 q b 6,8 (where q b ¼ 2π b ; b is the lattice constant, space group is Bmmb) which is smoothly tunable by substitution of the different rare-earth elements 25 . In addition, all members of the series except LaTe 3 and TmTe 3 are magnetic, with each of the members aside from LaTe 3 , TmTe 3 , and ErTe 3 ordering antiferromagnetically above 2 K [25][26][27][28] . While Fermi surface nesting had been assigned as the primary cause of the CDW in earlier work 6,29,30 , more recent studies 7,31 indicate that the CDW formation is driven by strongly momentum-dependent electron-phonon coupling.…”