Pure dephasing, the loss of a particle’s wave information without losing energy, actively controls where electrons move in off-diagonal Aubry, André, Harper quasicrystals according to Ming-Jie Tao of Chengdu University of Technology and colleagues from Hangzhou Normal University and Nankai University. Introducing pure dephasing into certain materials does not always destroy quantum localisation but instead actively reshapes it, creating new boundaries between different states of matter previously thought only weakened by such disruptions. Controlling electron movement in special quasicrystals now enables manipulation of electron flow through careful engineering of this disruptive effect and provides better understanding of energy dissipation.

Disorder typically destroys quantum localisation within materials; however, recent work challenges this assumption and reveals a surprising level of control through environmental interactions. These unique structures resemble an infinitely long mosaic made without repeating tiles, unlike conventional crystals with their regular patterns. This manipulation creates new boundaries on the material’s ‘energy landscape’, termed mobility edges, which separate areas allowing free electron movement from those trapping them. The team demonstrated these disruptions can even create anomalous mobility edges separating complex states; repeatedly crumpling paper represents how intricate electron behaviour becomes within these materials.

Pure dephasing induces emergent mobility edges in dimerized quasicrystals

Strong pure dephasing, the loss of a quantum wave’s information without energy change, can induce mobility edges within dimerized off-diagonal Aubry, André, Harper quasicrystals. These boundaries separate regions exhibiting distinct electron behaviours where previously none existed.

Anomalous mobility edges formed between multifractal critical and fully localised states, even when initial electronic states were already delocalised or exhibited complex behaviour; this represents an improvement over previous understanding which viewed such disturbances as purely detrimental to interference effects. Calculations simplified by applying adiabatic elimination, removing rapidly changing terms from equations describing electrons and allowing derivation of a classical model charting how dephasing relaxes electrons between different quantum states.

Lindblad master equation modelling of coherent electron relaxation via adiabatic elimination

Numerical analysis relied on solving the Lindblad master equation, a mathematical framework detailing evolution in quantum systems interacting with their environment. Employing adiabatic elimination within this framework streamlined calculations by discarding quickly fluctuating terms governing electron dynamics. This enabled derivation of an effective classical Markov transition matrix that charts electron relaxation between states due to pure dephasing, the loss of wave information without energy loss.

The resulting simplification proved key; it revealed that pure dephasing wasn’t merely disruptive but could actively induce distinct boundaries within the material’s electronic structure. A one-dimensional tight-binding model incorporating both lattice dimerization and off-diagonal quasiperiodic modulation used parameters such as hopping amplitude ‘t’ set to unity for defining the energy scale, dimerization strength λ, and quasiperiodic modulation amplitude V alongside irrational frequency α defined using Fibonacci numbers to ensure periodic boundary conditions were met during simulations, accounting for environmental interactions affecting real experiments.

Controlled disturbance unlocks new states in solid materials

The findings challenge long-held beliefs about the detrimental role of environmental ‘noise’, specifically pure dephasing, within these engineered materials. That carefully controlling it can actively create boundaries, known as mobility edges, separating regions where electrons move freely from those they trap is a significant discovery; some physicists remain sceptical about deliberately introducing disturbances into delicate quantum systems, which may seem counterintuitive. Controlled ‘noise sculpts electronic landscapes by inducing distinct mobility edges, boundaries separating areas with differing electron movement. Observations included not only conventional but also anomalous ones distinguishing complex multifractal states from fully localised areas, even when starting conditions showed delocalisation or complexity, demonstrating potential for tailoring material properties through careful control of dephasing effects.

The research demonstrated that pure dephasing, the loss of wave information without energy loss, can induce new mobility edges within a dimerized off-diagonal Aubry-Andre-Harper quasicrystal. This is unexpected because established theory suggests disturbances should disrupt localisation and encourage transport instead. The study revealed both standard and unusual boundaries separating regions with differing electron behaviour, including extended, multifractal critical, and localised states; the authors used numerical simulations to map out these different phases in the system’s relaxation spectrum. These findings suggest controlling dephasing offers a mechanism for manipulating electronic properties in dissipative quasicrystal systems.

👉 More information
🗞 Dephasing-induced distinct mobility edges in a dimerized off-diagonal quasicrystal
✍️ Ming-Jie Tao, Yi-Ting Wang, Jing Li, Hongsheng Hou, Xiang-Ping Jiang and Lei Pan
🧠 ArXiv: https://arxiv.org/abs/2608.17937

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