Spin excitations in the frustrated triangular lattice antiferromagnet NaYbO2

Long-range magnetic order in the ${\tilde S}=1/2$ triangular lattice antiferromagnet KCeS$_2$

“…It can possibly originate from a minority of Ce ions in a different surrounding, for instance in the vicinity of crystal defects such as stacking faults that are typical for the layered delafossite structure [56][57][58]. Similar additional CEF lines have been previously observed, for instance, in the isostructural NaYbO 2 [25], NaYbS 2 [19], NaYbSe 2 [28], and in the Ce pyrochlore Ce 2 Zr 2 O 7 [59].…”

“…For the two magnetic ions Ce 3+ or Yb 3+ , with electronic configurations of 4 f 1 and 4 f 13 , respectively, aS = 1/2 spin state can be achieved at low temperature due to the spin-orbit coupling in combination with the depopulation of higher-energy crystal electric field (CEF) levels [13,14,18,19]. Numerous Ybbased TLAF were recently reported and proposed to host a quantum spin liquid ground state: YbMgGaO 4 [13,20], NaYbO 2 [21][22][23][24][25], NaYbS 2 [19,21,26], NaYbSe 2 [21,27,28], KYbS 2 [29], CsYbSe 2 [30] and Yb(BaBO 3 ) 3 [31]. In addition, a putative QSL state was recently reported in the Ce-based TLAF CsCeSe 2 [30].…”

Fluctuating magnetic droplets immersed in a sea of quantum spin liquid

“…The ferrimagnetic droplets immersed in a sea of QSL is illustrated in Fig. 5, on which an upup-down magnetic structure forms within each droplet in accordance with field-induced magnetic orders in Yb 3+ compounds on triangular lattice 38,[41][42][43][44] . It is natural to assume that such a ferrimagnetic ordering state has slightly higher energy than the QSL state, which allows the nucleation of ferrimagnetic droplet around a defect.…”

“…All three compounds are free from long-range order (LRO) down to 50 mK determined from zero field (ZF) specific heat and µSR measurements [37][38][39][40] . Including CsYbSe2 with the same structure, all of them have field-induced magnetic orders 38,[41][42][43][44] . Very recently, the ground state of NaYbSe2 is claimed to be a QSL with spinon Fermi surface 45 .…”

“…The ratio between the residual entropy and the total magnetic entropy is estimated to be r ln(1+m/3) 𝑚𝑚 ln 2 , where r is the volume fraction of droplets and each droplet carries m Yb 3+ ions. It is expected that the size of the fluctuating droplets will be enhanced by an external magnetic field, resulting in a long ranged up-up-down magnetic order in bulk when the applied magnetic field exceeds some threshold 38,[41][42][43][44] .…”