Diagnosing quantum phase transition via holographic entanglement entropy at finite temperature

We investigate the behavior of the holographic entanglement entropy (HEE) in proximity to the quantum critical points (QCPs) of the metal-insulator transition (MIT) in the Einstein-Maxwell-dilaton-axions (EMDA) model. Due to the fact that the ground state entropy density of the EMDA model is vanishing for insulating phase, but non-vanishing for the metallic phase, we used to expect that it is the HEE itself that characterizes the QCPs. This expectation is validated for certain case, however, we make a noteworthy observation: for a specific scenario, it is not the HEE itself but rather the second-order derivative of HEE with respect to the lattice wave number that effectively characterizes the quantum phase transition (QPT). This distinction arises due to the influence of thermal effects. These findings present novel insights into the interplay between HEE and QPTs in the context of the MIT, and have significant implications for studying QPT at finite temperatures.Comment: 15 pages, 5 figure

Synthesis of Thiophene-Based Derivatives and the Effects of Their Molecular Structure on the Mesomorphic Behavior and Temperature Range of Liquid-Crystalline Blue Phases

The development of blue-phase liquid crystal (BPLC) materials with a wide temperature range is of great significance for practical applications in the optoelectronic field. In the study, bent-core derivatives with a 3-hexyl-2,5-disubstituted thiophene central ring in the λ-shaped molecular structure were designed and synthesized. Their mesomorphic behavior and effect on the blue-phase (BP) temperature range were investigated. Interestingly, a BP was achieved both during the heating and cooling processes by doping with a proper concentration of chiral compound into the thiophene bent-shaped molecule with high rigidity, while derivatives with fluorine atom substitution only exhibited cholesteric phase no matter how many chiral compounds were added. This result proved that BP is highly sensitive to the molecular structures of bent-shaped molecules. Moreover, the BP temperature range was broadened when adding these molecules into a BPLC host, which thus improved the BP temperature range from the initial value, no more than 4 °C, to as much as 24 °C. The experimental phenomena were reasonably explained through molecular simulation calculations. The study may provide some experimental basis and theoretical guidance for the design of novel bent-shaped molecules and BPLC material with a wide temperature range

Diagnosing quantum phase transitions via holographic entanglement entropy at finite temperature

We investigate the behavior of the holographic entanglement entropy (HEE) in proximity to the quantum critical points (QCPs) of the metal-insulator transition (MIT) in the Einstein–Maxwell-dilaton-axions (EMDA) model. Since both the metallic phase and the insulating phase are characterized by distinct IR geometries, we used to expect that the HEE itself characterizes the QCPs. This expectation is validated for certain cases, however, we make a noteworthy observation: for a specific scenario where $$-1<\gamma \le -1/3$$, with $$\gamma$$ as a coupling parameter, it is not the HEE itself but rather the second-order derivative of HEE with respect to the lattice wave number that effectively characterizes quantum phase transitions (QPTs). This distinction arises due to the influence of thermal effects. These findings present novel insights into the interplay between HEE and QPTs in the context of the MIT, and have significant implications for studying QPTs at finite temperatures