Spectroscopic evidence for negative electronic compressibility in a quasi-three-dimensional spin–orbit correlated metal

Abstract

Negative compressibility is a sign of thermodynamic instability of open [1][2][3] or non-equilibrium [4,5] systems. In quantum materials consisting of multiple mutually coupled subsystems, the compressibility of one subsystem can be negative if it is countered by positive compressibility of the others. Manifestations of this effect have so far been limited to low-dimensional dilute electron systems [6][7][8][9][10][11]. Here we present evidence from angle-resolved photoemission spectroscopy (ARPES) for negative electronic compressibility (NEC) in the quasi-three-dimensional (3D) spinorbit correlated metal (Sr 1−x La x ) 3 Ir 2 O 7 . Increased electron filling accompanies an anomalous decrease of the chemical potential, as indicated by the overall movement of the deep valence bands.Such anomaly, suggestive of NEC, is shown to be primarily driven by the lowering in energy of the conduction band as the correlated bandgap reduces. Our finding points to a distinct pathway towards an uncharted territory of NEC featuring bulk correlated metals with unique potential for applications in low-power nanoelectronics and novel metamaterials.

Negative electronic compressibility and tunable spin splitting in WSe2

“…Unlike in the case of bulk doping, 27 however, here the emergence of NEC is intricately linked to single-particle band structure changes as a consequence of electrostatic band bending potentials and resultant quantum size effects. To disentangle these, we show in Fig.…”

Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr1−xLax)3Lu1, McNally2, Sala3 et al. 2017Phys. Rev. Lett.348380View full textAdd to dashboardCite

“…The strong interlayer couplings and magnetic anisotropy including the bonddirectional pseudodipolar interactions arising from the J eff = . In contrast, a doping-dependent negative electronic compressibility was discovered in later ARPES measurements, indicating an exotic correlated metallic state [32,35]. In order to reveal the nature of the metallic state, a detailed study of the elementary excitations is required that can determine the doping evolution of the electronic interactions, especially the magnetic couplings.…”

First-Order Melting of a Weak Spin-Orbit Mott Insulator into a Correlated Metal

“…Realizing new electronic phases in close proximity to this SOM state is a subject of considerable theoretical work [5], and recent experiments have begun to suggest exotic properties present in nearby metallic states [6,7]. However, the central task of understanding the mechanism of the Mott state's collapse in these 5d-electron Mott systems remains an open question, where, for instance, the roles of competing phases and additional modes of symmetry breaking remain unaddressed.…”

“…However, little remains understood regarding the nature of the metallic state realized upon carrier substitution and the means through which the parent J eff ¼ 1=2 Mott state collapses. For instance, once the Mott state is destabilized, conflicting reports have suggested both an unusual metallic state with a negative electronic compressibility [7] as well as a surprisingly conventional, weakly correlated metal [14]. Notably lacking is a detailed understanding of the structural and electronic responses of this prototypical weak SOM system as electrons are introduced.…”