Large thermopower from dressed quasiparticles in the layered cobaltates and rhodates

Anomalous band renormalization due to a high-energy kink in K0.65RhO2 with colossal thermoelectric power factor

“…Next, comparing our experimental band structure with the available ARPES data on these type of systems, analogous to Na x CoO 2 [27,28,31] and Li x CoO 2 [32], we could also observe only one circular-shaped hole pocket from the Fermi surface map. Most importantly, in agreement with the previous report on K 0.62 RhO 2 [29], we identified an antiband crossing at ≈0.4 eV below E F in the -K direction. Furthermore, the top of hole-like band at the K point is found nearly at the same binding energy of 0.25 eV.…”

“…On the other hand, K x RhO 2 a similar layered compound does not seem to be showing the physical properties as diverse as Na x CoO 2 . It was reported to show a large thermoelectric power [15,25,26], but still is half to that of Na x CoO 2 [13], despite both showing e-ph interactions at a Debye frequency of 70-75 meV [27][28][29]. Earlier ARPES report on K x RhO 2 hinted at the importance of electron-boson scattering for the * setti@bose.res.in recorded high thermopowers [29].…”

“…It was reported to show a large thermoelectric power [15,25,26], but still is half to that of Na x CoO 2 [13], despite both showing e-ph interactions at a Debye frequency of 70-75 meV [27][28][29]. Earlier ARPES report on K x RhO 2 hinted at the importance of electron-boson scattering for the * setti@bose.res.in recorded high thermopowers [29]. In this contribution, we study the effect of electronic correlation on the low-energy electronic structure of the layered K 0.65(2) RhO 2 single crystal using ultrahigh energy resolution ARPES technique and DFT calculations [30].…”

Suppression of magnetism and Seebeck effect in Na0.875CoO2 induced by SbCo dopants

“…1, all Co ions have, indeed, an oxidation state of + 3. Additionally, all Co ions were stabilised in the low spin configuration of t 6 2g e 0 g , further suggesting that this compound is non-magnetic. This is in contrast to the pristine Na 0.875 CoO 2 compounds in which the Co 4+ ions were antiferromagnetically aligned across the CoO 2 planes [56,57].…”

“…Na x CoO 2 ′s unit cell consists of two alternating Na layers and edge-sharing CoO 6 octahedra. Co ions' mixed valency in Na deficient Na x CoO 2 (x < 1) creates a large spin entropy flow, and consequently, a large Seebeck coefficient [6]. Additionally, the Na layer in which Na + ions are amorphous and liquid like at room temperature [7] strongly scatters the heat-carrying phonons.…”