Quantum phase transitions (QPTs) driven by quantum fluctuations are transitions between distinct quantum phases of matter. At present, they are poorly understood and not readily controlled. Here, scanning tunneling microscopy (STM) and noncontact atomic force microscopy (nc-AFM) are used to explore atomic scale control over quantum phase transitions between two different topological quantum states of a well-defined π-conjugated polymer. The phase transition is driven by a pseudo Jahn-Teller effect that is activated above a certain polymer chain length. In addition, theoretical calculations indicate the presence of long-lasting coherent fluctuations between the polymer's two quantum phases near the phase transition, at finite temperature. This work thus presents a new way of exploring atomic-scale control over QPTs and indicates that emerging quantum criticality in the vicinity of a QPT can give rise to new states of organic matter.
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http://dx.doi.org/10.1002/adma.202104495 | DOI Listing |
Molecules
December 2024
Institute of Ion Physics and Applied Physics, University of Innsbruck, Technikerstraße 25, 6020 Innsbruck, Austria.
Machine learning potential energy functions can drive the atomistic dynamics of molecules, clusters, and condensed phases. They are amongst the first examples that showed how quantum mechanics together with machine learning can predict chemical reactions as well as material properties and even lead to new materials. In this work, we study the behaviour of tungsten trioxide (WO) surfaces upon particle impact by employing potential energy surfaces represented by neural networks.
View Article and Find Full Text PDFMaterials (Basel)
December 2024
Department of Applied Physics, Institute of Natural Sciences, Kyung Hee University, Yongin 17104, Republic of Korea.
SrCu(BO) (Sr-122) has attracted considerable interest as a quasi-two-dimensional S = 1/2 Heisenberg antiferromagnetic spin system with a Shastry-Sutherland lattice (SSL) structure. It features a Cu spin dimer ground state and exhibits intra-dimer Dzyaloshinskii-Moriya interactions, making Sr-122 a fascinating platform for studying quantum magnetic phenomena. In this study, we investigate the β-phase of SrCu(BO) (β-Sr-212), which retains the same spin structure as Sr-122, to explore how the carrier concentration affects the spin gap.
View Article and Find Full Text PDFEntropy (Basel)
December 2024
Information Science and Technology College, Dalian Maritime University, Dalian 116026, China.
In this paper, by using eleven entangled quantum states as a quantum channel, we propose a cyclic and asymmetric novel protocol for four participants in which both Alice and Bob can transmit two-qubit states, and Charlie can transmit three-qubit states with the assistance of the supervisor David, who provides a guarantee for communication security. This protocol is based on GHZ state measurement (GHZ), single-qubit measurement (SM), and unitary operations (UO) to implement the communication task. The analysis demonstrates that the success probability of the proposed protocol can reach 100%.
View Article and Find Full Text PDFEntropy (Basel)
December 2024
Instituto de Física Teórica, CSIC-Universidad Autónoma de Madrid, 28049 Madrid, Spain.
In this work, we propose an information theoretic order parameter able to characterize the presence and breaking of categorical symmetries in (1+1)-d rational conformal field theories (RCFTs). Specifically, we compute the quantum relative entropy between the ground states of RCFTs representing the critical point of phase transitions between different symmetry-broken phases of theories with categorical symmetries, and their symmetrized versions. We find that, at leading order in the high temperature limit, this relative entropy only depends on the expectation values of the quantum dimensions of the topological operators implementing the categorical symmetry.
View Article and Find Full Text PDFEntropy (Basel)
December 2024
Department of Physics, Federal Technological Education Center of Minas Gerais, Belo Horizonte 30510-000, MG, Brazil.
In this paper, we analyzed the influence of the spin Nernst effect on quantum correlation in a layered ferrimagnetic model. In the study of three-dimensional ferrimagnets, the focus is on materials with a specific arrangement of spins, where the neighboring spins are parallel and the others are antiparallel. The anisotropic nature of these materials means that the interactions between spins depend on their relative orientations in different directions.
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