Pressure-Temperature Phase Diagram of Golden SmS

黑色SmS中的电流诱导金属化与价态转变

Current-Induced Metallization and Valence Transition in Black SmS

本文通过光谱实验研究黑色SmS的电流诱导绝缘体-金属转变，发现电流增强Sm 4f-5d杂化，导致载流子密度增加和价态转变。

SmS中的光致非线性能带移动与价态转变

Photo-induced nonlinear band shift and valence transition in SmS

该研究利用时间分辨光电子能谱揭示SmS中Sm 4f能带的非线性光致移动，区分表面光电压效应与超快价态转变，并指出光激发可抵达金属相边界。

Surface valence transition in SmS by alkali metal adsorption

The electronic structure changes of SmS surfaces under potassium (K) doping are elucidated using synchrotron-based core-level photoelectron spectroscopy and angle-resolved photoelectron spectroscopy (ARPES). The Sm core-level and ARPES spectra indicate that the Sm mean valence of the surface increased from the nearly divalent to trivalent states, with increasing K deposition. Carrier-induced valence transition (CIVT) from Sm$^{2+}$ to Sm$^{3+}$ exhibits a behavior opposite to that under conventional electron doping. Excess electrons are trapped by isolated excitons, which is inconsistent with …

Pressure induced electronic transitions in Samarium monochalcogenides

Pressure induced isostructural insulator to metal transition for SmS is characterised by the presence of an intermediate valence state at higher pressure which cannot be captured by the density functional theory. As a direct outcome of including the charge and spin fluctuations incorporated in dynamical mean field theory, we see the emergence of insulating and metallic phases with increasing pressure as a function of changing valence. This is accompanied by significantly improved predictions of the equilibrium lattice constants and bulk moduli for all Sm-monochalcogenides verifying experiments…

Nonmagnetic-magnetic transition and magnetically ordered structure in SmS

SmS, a prototypical intermediate valence compound, has been studied by performing high-pressure nuclear magnetic resonance measurements on a $^{33}$S-enriched sample. The observation of an additional signal below 15-20 K above a nonmagnetic-magnetic transition pressure $P_{\rm c2} \approx 2$ GPa gives evidence of a magnetic transition. The absence of a Curie-term in the Knight shift near $P_{\rm c2}$ indicates that the localized character of $4f$ electrons is entirely screened and the mechanism of the magnetic ordering is not described within a simple localized model. Simultaneously, the line …

Infrared Conductivity of Elemental Bismuth under Pressure: Evidence for an Avoided Lifshitz-Type Semimetal-Semiconductor Transition

The application of pressure to elemental bismuth reduces its conduction-valence band overlap, and results in a semimetal-semiconductor (SMSC) transition around 25 kbar. This transition is nominally of the topological "Lifshitz" Fermi surface variety, but there are open questions about the role of interactions at low charge densities. Using a novel pressure cell with optical access, we have performed an extensive study of bismuth's infrared conductivity under pressure. In contrast to the expected pure band behavior we find signatures of enhanced interaction effects, including strongly coupled c…

Valence and magnetic instabilities in Sm compounds at high pressures

We report on the study of the response to high pressures of the electronic and magnetic properties of several Sm-based compounds, which span at ambient pressure the whole range of stable charge states between the divalent and the trivalent. Our nuclear forward scattering of synchrotron radiation and specific heat investigations show that in both golden SmS and SmB6 the pressure-induced insulator to metal transitions (at 2 and about 4-7 GPa, respectively) are associated with the onset of long-range magnetic order, stable up to at least 19 and 26 GPa, respectively. This long-range magnetic order…

Valence and magnetic ordering in intermediate valence compounds : TmSe versus SmB6

The intermediate valent systems TmSe and SmB6 have been investigated up to 16 and 18 GPa by ac microcalorimetry with a pressure (p) tuning realized in situ at low temperature. For TmSe, the transition from an antiferromagnetic insulator for p<3 GPa to an antiferromagnetic metal at higher pressure has been confirmed. A drastic change in the p variation of the Neel temperature (Tn) is observed at 3 GPa. In the metallic phase (p>3 GPa), Tn is found to increase linearly with p. A similar linear p increase of Tn is observed for the quasitrivalent compound TmS which is at ambiant pressure equivalent…

Solid-solid volume collapse transitions are zeroth order

We present an exactly solvable non-linear elastic model of a volume collapse transition in an isotropic solid. Integrity of the lattice through the transition leads to an infinite-range density-density interaction, which drives classical critical behavior. Nucleation is forbidden within a pressure window leading to intrinsic hysteresis and an unavoidable discontinuity of the thermodynamic potential (zeroth order transition). The window shrinks with increasing temperature ending at a critical point at a temperature related to the shear modulus. Mixed phases behave non-extensively and show negat…

黑色一硫化钐的光致相变

Photo-induced phase transition on black samarium monosulfide

本文通过光激发产生激子研究SmS的相变机制，发现仅靠产生激子无法实现其从黑色绝缘体到金黄色金属的相变，还需晶格收缩等其他效应。