arXiv subjects

Chengchao Zhong

Publications and source records attributed to Chengchao Zhong.

4 recordsLinked to original sources

arXiv2023

Honeycomb Layered Frameworks with Metallophilic Bilayers

This Review highlights the exciting advancements in the science of honeycomb layered frameworks with metallophilic bilayers that have recently garnered attention particularly due to reports of anomalous fractional valency states of silver cations sandwiched between transition metal slabs of other cations. First, the latest tactics and techniques including but not limited to X-ray absorption spectroscopy (XAS) and high-resolution transmission electron microscopy (HRTEM) particularly necessary for characterising recent honeycomb layered frameworks with metallophilic bilayers are described, with emphasis on silver-based oxides. Second, new strategies and concepts related to topochemically- or temperature-induced cationic-deficient phases expanding the compositional space of honeycomb layered frameworks focused on cationic bilayer architectures are also accentuated. Third, the latest condensed matter theoretic advances towards a full, atomistic description of the bilayered structure in such frameworks are detailed, especially related to critical phenomena at the cusp of the monolayer-bilayer phase transition. This entails, in part, describing honeycomb layered frameworks as optimised lattices within the congruent sphere packing problem, equivalent to a particular two-dimensional (2D) conformal field theory. Altogether, it is hoped that this Review will give the reader a panoramic view of the honeycomb layered frameworks with important applications within the emerging field of quantum matter, potentially redefining their frontier. Thus, the scope of this Review is expected to be worthwhile for recent graduates and emerging experts alike not only in the materials science and chemistry community but also in other diverse fields of interest.

cond-mat.mtrl-sci↗

arXiv2023

Simultaneous measurement of specific heat and thermal conductivity in pulsed magnetic fields

We report an experimental setup for simultaneously measuring specific heat and thermal conductivity in feedback-controlled pulsed magnetic fields of 50 msec duration at cryogenic temperatures. A stabilized magnetic field pulse obtained by the feedback control, which dramatically improves the thermal stability of the setup and sample, is used in combination with the flash method to obtain absolute values of thermal properties up to 37.2 T in the 2 K to 16 K temperature range. We describe the experimental setup and demonstrate the performance of the present method with measurements on single crystal samples of the geometrically frustrated quantum spin-dimer system SrCu$_2$(BO$_3$)$_2$. Our proof-of-principle results show excellent agreement with data taken using a standard steady-state method, confirming the validity and convenience of the present approach.

cond-mat.str-el↗

arXiv2022

Magnetically hidden state on the ground floor of the magnetic Devil's staircase

We investigated the low-temperature and high-field thermodynamic and ultrasonic properties of SrCu2(BO3)2, which exhibits various plateaux in its magnetization curve above 27~T, called a magnetic Devil's staircase. The results of the present study confirm that magnetic crystallization, the first step of the staircase, occurs above 27~T as a 1st-order transition accompanied by a sharp singularity in heat capacity $C_p$ and a kink in the elastic constant. In addition, we observe a thermodynamic anomaly at lower fields around 26~T, which has not been previously detected by any magnetic probes. At low temperatures, this magnetically hidden state has a large entropy and does not exhibit Schottky-type gapped behavior, which suggests the existence of low-energy collective excitations. Based on our observations and theoretical predictions, we propose that magnetic quadrupoles form a spin-nematic state around 26~T as a hidden state on the ground floor of the magnetic Devil's staircase.

cond-mat.str-el↗

arXiv2021

Thermally populated versus field-induced triplon bound states in the Shastry-Sutherland lattice SrCu$_2$(BO$_3$)$_2$

The Shastry-Sutherland compound SrCu$_2$(BO$_3$)$_2$ constituting orthogonally coupled dimers harbors a $S=0$ singlet ground state. The confluence of strong interdimer interaction and frustration engenders a spectrum of low-energy excitations including localized triplons as well as singlet and triplet bound states. Their dynamics are controlled by an external magnetic field and temperature. Here, we employ high-field Raman spectroscopy to map the field and temperature evolution of such bosonic composite quasiparticles on approaching the 1/8 magnetization plateau. Our study unveils that the magnetic field and thermal fluctuations show remarkably similar effects in melting the singlet bound states, but are disparate in their effects on the fine spectral shapes. This, together with the anti-crossing of two singlet bound states in the intermediate field $B=10-16$ T, is discussed in terms of the correlated dynamics of frustrated, interacting bosons.

cond-mat.str-el↗