Direct experimental observation of the molecular J eff = 3/2 ground state in the lacunar spinel GaTa4Se8

Abstract

Strong spin–orbit coupling lifts the degeneracy of t 2g orbitals in 5d transition-metal systems, leaving a Kramers doublet and quartet with effective angular momentum of J eff = 1/2 and 3/2, respectively. These spin–orbit entangled states can host exotic quantum phases such as topological Mott state, unconventional superconductivity, and quantum spin liquid. The lacunar spinel GaTa4Se8 was theoretically predicted to form the molecular J eff = 3/2 ground state. Experimental verification of its existence is an important first step to exploring the consequences of the J eff = 3/2 state. Here, we report direct experimental evidence of the J eff = 3/2 state in GaTa4Se8 by means of excitation spectra of resonant inelastic X-ray scattering at the Ta L3 and L2 edges. We find that the excitations involving the J eff = 1/2 molecular orbital are absent only at the Ta L2 edge, manifesting the realization of the molecular J eff = 3/2 ground state in GaTa4Se8.

WITHDRAWN: Discovery of New Metallic and Superconducting Phase in GaTa4Se8 Under High Pressure

“…Given that DFT + U is such a method that highly overestimates the magnetic moment formation tendency, it is a strong evidence that Metal 2 is non-magnetic, and its ground state is far from the magnetic instability. Therefore, it is clearly different from the lower pressure metallic phases for which the well-defined Jeff = 3/2 moment is revealed by previous RIXS experiment, DFT + U, and DFT + DMFT calculations [17][18][19] .…”

“…Although GTS has long been known as paramagnetic 11 down to low temperature, its magnetic property has recently drawn much attention after the theoretical and experimental reports of a socalled molecular Jeff = 3/2 moment residing in this material [17][18][19] . This novel magnetic ground state is a concerted result of triply-degenerated t2 molecular orbitals and strong spin-orbit coupling (SOC).…”

“…3(g). In the low-pressure phases, the well-defined molecular Jeff = 3/2 and 1/2 bands are clearly identified by taking SOC into account[17][18][19] . On the other hand, in this high-pressure regime, the molecular orbitals are not well defined and the projection onto the Jeff state fails, implying that this compound's molecular nature is no longer retained; seeFig.…”

Rank–2 U(1) Spin Liquid on the Breathing Pyrochlore Lattice

“…Breathing-pyrochlore magnets were first studied as a tractable limit of the pyrochlore HAF [69][70][71][72], but have since been realised in materials based on both transition-metal [73][74][75][76][77] and rareearth ions [78,79]. Interesting parallels are also found in lacunar spinels [80,81]. To date, most theoretical work has concentrated on SU (2)-invariant models [69][70][71][72][82][83][84].…”

Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model

“…The case of two holes in the t 2g shell might correspond to SrRuO 3 [11,12], and that of one hole to SrRhO 3 [13], to mention just a few widely studied perovskite compounds. The same model is also used in studies of alkali-doped fullerides with half-filled molecular orbitals with t 1u symmetry [14][15][16][17][18] and for the description of lacunar spinels GaM 4 X 8 , which are characterized by M 4 X 4 "molecules" [19][20][21][22]. More generally, the three-orbital Hubbard model plays an important role in theoretical studies which try to reveal and quantify the correlation effects resulting from the Coulomb interaction in a multiorbital setup [23][24][25][26][27].…”