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Register a new userEvidence of structural evolution in Sr2RhO4 studied by time-resolved optical reflectivity spectroscopy
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We investigate ultrafast dynamics from photoinduced reflectivity of Sr2RhO4 by using femtosecond near-infrared pulses. We observe a clear temperature-dependent anomaly in its electronic dynamics which slows down below 160 K. In addition, coherent oscillations of the A1g symmetric 5.3-THz phonon exhibit a 90-degree shift in its initial phase across TS, indicating a structural change in octahedral rotation distortions. We propose that octahedral structure in Sr2RhO4 evolves at around TS, and it can influence on the non-equilibrium dynamics of photoinduced carriers as well as real-time phonon responses.
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We report on systematic investigation of hot carrier dynamics in Ti4O7 by ultrafast time-resolved optical reflectivity. We find the transient indication for its two-step insulator-metal (I-M) transition, in which two phase transitions occur from long-range order bipolaron low-temperature insulating (LI) phase to disordered bipolaron high-temperature insulating (HI) phase at Tc1 and to free carrier metallic (M) phase at Tc2. Our results reveal that photoexcitation can effectively lower down both Tc1 and Tc2 with pump fluence increasing, allowing a light-control of I-M transition. We address a phase diagram that provides a framework for the photoinduced I-M transition and helps the potential use of Ti4O7 for photoelectric and thermoelectric devices.
We investigate the hot carrier dynamics of ZrTe$_5$ by ultrafast time-resolved optical reflectivity. Our results reveal a phonon-mediated across-gap recombination, consistent with its temperature-dependent gap nature as observed previously by photoemission. In addition, two distinct relaxations with a kink feature right after initial photoexcitation are well resolved, suggesting the complexity of electron thermalization process. Our findings indicate that correlated many-body effects play important role for the transient dynamics of ZrTe$_5$.
The localized-to-itinerant transition of f electrons lies at the heart of heavy-fermion physics, but has only been directly observed in single-layer Ce-based materials. Here, we report a comprehensive study on the electronic structure and nature of the Ce 4f electrons in the heavy-fermion superconductor Ce2PdIn8, a typical n=2 CenMmIn3n+2m compound, using high-resolution and 4d-4f resonance photoemission spectroscopies. The electronic structure of this material has been studied over a wide temperature range, and hybridization between f and conduction electrons can be clearly observed to form a Kondo resonance near the Fermi level at low temperatures. The characteristic temperature of the localized-to-itinerant transition is around 120K, which is much higher than its coherence temperature Tcoh~30K.
We use angle-resolved photoemission spectroscopy to study heavy fermion superconductor Ce2RhIn8. The Fermi surface is rather complicated and consists of several hole and electron pock- ets. We do not observe kz dispersion of Fermi sheets, which is consistent with 2D character of the electronic structure. Comparison of the ARPES data and band structure calculations points to a localized picture of f electrons. Our findings pave the way for understanding the transport and thermodynamical properties of this material.
We systemically investigate the nature of Ce 4f electrons in structurally layered heavy-fermion compounds CcmMnIn3m+2n (with M =Co, Rh, Ir, and Pt, m=l, 2, n=0 - 2), at low temperature using on-resonance angle-resolved photoemission spectroscopy. Three heavy quasiparticle bands f^0, f^1_7/2 and f^1_5/2 are observed in all compounds, but their intensities and energy locations vary greatly with materials. The strong f^0 states imply that the localized electron behavior dominates the Ce 4f states. The Ce 4f electrons are partially hybridized with the conduction electrons, making them have the dual nature of localization and itinerant. Our quantitative comparison reveals that the f^1_5/2 / f^0 intensity ratio is more suitable to reflect the 4f-state hybridization strength.
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