Thermoelectric Power Investigation on SmS

Imura, Keiichiro; Kanematsu, Shinkichi; Deguchi, K.; Suzuki, Hiroyuki; Matsubayashi, Kazuyuki; Sato, Noriaki

doi:10.1143/jpsjs.80sa.sa077

Cited by 7 publications

(6 citation statements)

References 13 publications

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“…Compared with our previous data taken by a dc method, the signal-to-noise ratio was markedly improved. 12 When external pressure was applied, the pressure cell (a NiCrAl -BeCu hybrid piston cylinder cell) was heated to about 320 K to reduce inhomogeneity arising from the solidification of Daphne oil (see discussion below for details). The pressure at low temperatures was determined by the superconducting transition temperature of indium.…”

Section: Experimental Methodsmentioning

confidence: 99%

Pressure–Temperature Phase Diagram of Golden SmS

et al. 2009

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We measured the thermal expansion of the valence fluctuating phase of SmS (golden SmS) to construct a pressure vs temperature phase diagram. The obtained phase diagram is characterized by three lines. One is a crossover line that divides the paramagnetic phase into two regions. The other two lines correspond to a second-order Néel transition and a first-order Néel transition. The crossover line appears to emerge from a tricritical point that separates the first-order Néel transition from the second-order one. We argue that a valence jump occurs at the border of antiferromagnetism.

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Section: Experimental Methodsmentioning

confidence: 99%

Pressure–Temperature Phase Diagram of Golden SmS

et al. 2009

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“…From these results, we suggest that the valence reduction with decreasing temperature is related to the pseudogap formation. In this study, we could not reach two important characteristic temperatures T 0 and T N : At the former temperature, the thermal expansion coefficient and the thermoelectric power show a broad negative peak [6], and at the latter temperature, the Néel ordering occurs. It is interesting to study how the Sm mean-valence behaves near these temperatures, especially at T 0 below which the resistivity drastically increases [6].…”

Section: Temperature Dependence Of Sm Mean-valencementioning

confidence: 55%

“…The high-pressure phase of SmS (referred to as g-SmS hereafter), which is a volume-collapsed phase of the semiconducting black-SmS with an indirect bandgap, is a typical intermediate-valence (IV) compound possessing 4 f 5 and 4 f 6 configurations [4,5]. The g-SmS shows intriguing physical properties which cannot be understood from a simple model, such as a non-metallic electrical resistivity, a rapid variation in Hall coefficient with temperature, and a broad negative maximum in temperature dependence of the thermoelectric power [6]. We particularly note that Schottky anomaly appears in specific heat and thermal expansion measurements, indicating a pseudogap formation at low temperature between P c1 and P c2 [7].…”

Section: Introductionmentioning

confidence: 99%

Pressure and Temperature Evolution of Sm Mean-Valence in Golden SmS

Imura

Suzuki

Kawade

et al. 2020

Proceedings of the International Conference on Strongly Correlated Electron Systems (SCES2019)

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We have performed Sm-L 3 edge x-ray absorption spectroscopy measurement of intermediate-valence (IV) compound SmS in high-resolution partial fluorescence yield mode (PFY-XAS) under pressure and low temperature. Incident energy dependence of the PFY intensity significantly changes at a critical pressure P c1 where a valence transition occurs from divalent to IV state. In the pressure region of P > P c1 , in which a pseudogap opens, the Sm mean-valence slightly decreases with lowering temperature. When the pressure is increased above P c2 where a magnetic ordering appears and the pseudogap disappears, the Sm mean-valence does not show clear variation with temperature. These results give us a new insight into the role of valence fluctuation in the pseudogap formation of SmS.

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“…19. Experimental details of transport, thermal expansion, and thermoelectric power were described elsewhere [20,21]. DC magnetization was measured by a commercial SQUID magnetometer.…”

Section: +mentioning

confidence: 99%

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

et al. 2011

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Golden SmS is a paramagnetic, mixed-valence system with a pseudogap. With increasing pressure across a critical pressure Pc, the system undergoes a discontinuous transition into a metallic, antiferromagnetically ordered state. By using a combination of thermodynamic, transport, and magnetic measurements, we show that the pseudogap results from the formation of a local bound state with spin singlet. We further argue that the transition Pc is regarded as a transition from an insulating electron-hole gas to a Kondo metal, i.e., from a spatially bound state to a Kondo virtually bound state between 4f and conduction electrons.PACS numbers: 65.40. De, 71.27.+a, 75.30 -6], which are ascribed to the interplay between 4f and conduction electrons. In these mixedvalence compounds, Coulomb repulsion between 4f electrons gives rise to a gap formation on the order 10 meV at the Fermi level. While such materials behave like a Kondo metal at temperatures (T ) higher than the gap energy, they show insulating behavior at low T . For SmB 6 , the collapse of the insulating gap and the emergence of a magnetic order occur at the same pressure [7,8], which suggests that the gap formation competes with the longrange magnetic ordering.Nonalloyed SmS undergoes a phase transition under pressure (P ). With increasing P , the system undergoes a valence transition at a critical pressure of approximately P = 0.7 GPa at T = 300 K from divalence to mixed valence, accompanied by a color change from black to golden yellow [9]. In this mixed-valence phase (named golden SmS), two configurations of 4f 6 and 4f 5 are energetically degenerate:This is also described formally as (1 − ǫ) Sm 2+ + ǫ Sm 3+with 0 ≤ ǫ ≤1, which leads to the definition of the mean valence as ν = 2(1 − ǫ) + 3ǫ. Note that the Sm 2+ ion has no magnetic moment owing to the vanishment of total angular momentum. As seen from Fig. 1(a), ν estimated from high-T experiments shows a continuous evolution with P [10-12]. A similar smooth P -variation is observed in the conductivity σ measured at T = 150 K [ Fig. 1(b)]. From these results, it is inferred that the number of electrons e on the right-hand side of eq. (1) monotonically * Present address: UVSOR Facility, Institute for Molecular Science, Okazaki 444-8585, Japan.E-mail address: imura@ims@ac.jp † E-mail address: kensho@cc.nagoya-u.ac.jp increases with P . As seen from the phase diagram of Fig. 1(c), there is no phase transition as a function of P at high T .At low T , by contrast, a magnetic transition occurs at P c ∼ 1.8 GPa [13,14]. Magnetic susceptibility revealed that the ground state at P > P c is antiferromagnetic

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Thermoelectric Power Investigation on SmS

Cited by 7 publications

References 13 publications

Pressure–Temperature Phase Diagram of Golden SmS

Pressure–Temperature Phase Diagram of Golden SmS

Pressure and Temperature Evolution of Sm Mean-Valence in Golden SmS

Discontinuous Transition from a Real Bound State to Virtual Bound State in a Mixed-Valence State of SmS

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