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Dynamical Realization of Coherent Structures in Condensed Matter

This presentation discusses the concepts of quantum coherence and coherence domains in condensed matter systems. It explores the formation of highly ordered structures and the role of temperature in coherent interactions. The analysis includes the study of matter as waves and the impact of the radiation field. The talk also examines the phenomenon of violation of asymptotic freedom and the theoretical consequences of quantum coherence in matter at finite temperature.

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Dynamical Realization of Coherent Structures in Condensed Matter

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  1. Coherence 2006 Roma - April 21th, 2006 Dynamical Realization of Coherent Structures in Condensed Matter Luca Gamberale Pirelli Labs – Materials Innovation Advanced Research (Milano, Italy)

  2. Summary • Overview of the ideas on Quantum Coherence and Coherence Domain • Coherent States: a simplified approach • The effect of temperature • Coherent Interactions

  3. Condensed Matter • How can a system of weakly interacting atoms organize itself and form highly ordered structures over large scales? Examples: Superfluidity/Superconductivity Biological Systems • Crystals Gas/Liquid/Solid Phase

  4. “Orthodox” description Paradigm of electrostatic hooks Question: Is the interaction between neighbors sufficientto guarantee long-range order? An interesting example: like-charge attraction Observation of long-ranged many-body attractive forces among sub-micron latex sheres suspended in water, that cannot be explained by means of short-range electrostatic interactions A.E.Larsen, D.G.Grier, Nature 385, 230 (1997)

  5. QED: a critical analysis • Matter has been traditionally considered as a collection of PARTICLES. What happens if we treat matter as a WAVE? Matter states are eigenvectors of number operator Quantum Phase completely undefined the radiation field is screened and may be neglected Matter states are eigenvectors of destruction operator Quantum Phase completely fixed the radiation field cannot be neglected in some circumstances

  6. Contribution of order N NEGATIVE! What happens if we take into account the radiation field? Matter Field Short-Range Free e.m. field Matter-Field Interaction (usually neglected) A2-term (required by gauge-invariance) A careful analysis shows that COHERENT CONFIGURATIONS exist whose energy is LOWER than those at zero-field Symmetry Breaking

  7. Coherent condensation of a system of N identical particles Not equivalent to Long range!! Ex: Bose condensate Definition of quantum coherence Slow (classical) evolution Locked phase Quantum fluctuation Random phase Complex plane

  8. Two-level system The simplest of the many-body systems But... of enormous physical importance Atomic Energy Levels Many-level system Two-level approximation

  9. Electromagnetic field Matter Field Coherence equations for the Two-level system(Preparata Equations) Interaction term Not present in laser eqs. Responsible for runaway

  10. Electromagnetic structure of a single Coherence Domain The e.m. field has the same phase for each point of the CD Quantum phase

  11. Total Reflection of trapped em field • CD does not radiate because Poynting vector has zero mean value • Due to frequency renormalization, photons cannot radiate because off-shell Total reflection: a natural ‘trapped’ laser

  12. Structure of bulk matter Condensed Matter is viewed as a collection of COHERENCE DOMAINS 2-fluid model Domain (Coherent Matter) Fluctuations (Incoherent Matter)

  13. Coherent states: a simplified approach S. Sivasubramanian, A. Widom, and Y. N. Srivastava, Physica A 301, 241 (2001).

  14. EM Glauber state The trial Quantum State Matter field Anzats Full variational quantum state

  15. Evaluation of the energy-per-particle Minimum exists when

  16. Graphical representation of the energy

  17. Energy as a function of density (example)

  18. Important Remarks 1/2 Condensation occurs only if we have and this happens only if the matter field has a modulation with period The ith atom is in a configuration TOTALLY delocalized in space, in contrast with the particle-like character of its incoherent counterpart The wave function of the single atoms in the coherent state is different from that of the lowest energy state without em condensate, since it contains a certain fraction of the excited state. This very important issue implies that, when matter interacts with external fields, it may exhibit unexpected behavior, a phenomenon referred to as violation of asymptotic freedom.

  19. Important remarks 2/2 Simplified approach not applicable in this form to liquid water because of important dispersive contributions arising from excited levels of the water molecule (developed by G.Preparata and E.Del Giudice). Complete revision of theory and numerical calculations is presently under way (myself and E.Del Giudice).

  20. Forbidden Energy of a coherent domain. The effect of temperature Two-fluid picture Incoherent (thermal) Excitations Boltzmann-distributed Quasi-particle excitations (Bogoliubov Spectrum) Normal Perturbative energy Energy Gap (per particle) Coherent Zero-temperature coherent particles

  21. The effect of temperature w w Free particles massons Free particles massons rotons T=0 phonons rotons T>0 phonons k k Coherent phase Coherent phase 1° sound w Free particles massons Quasi-particle spectrum (Bogoliubov) rotons T>>0 phonons k Coherent phase (progressively depleted)

  22. Theoretical consequences of quantum coherence in matter at finite temperature • The existence of coherent configurations in matter implies the emergence of COHERENT SCATTERING Incoherent scattering Kinematics completely different! Coherent scattering

  23. Coherent interactions: features • Increased probability of interaction by orders of magnitude • Different kinematics • Extremely low energy exchange • Virtually no entropy generation • Non-local interaction • Seems adequate to the description of BIOLOGICAL PROCESSES When • Energy exchanged unable to overcome the energy gap In most cases both coherent and incoherent interactions occur (e.g. Moessbauer effect) with relative balance depending on temperature

  24. Forbidden Conditions for coherent scattering Incident particle must not be able to overcome the coherent energy gap Incident particle Phonon excitations Perturbative energy Energy Gap (per particle)

  25. Quantum Coherent Interactions N scatterers Quantum phase Quantum incoherent Quantum coherent Cross section goes like N Cross section goes like N2 N~1023 !!!

  26. Conclusions Conclusions • The generally accepted theory of condensed matter misses the contribution of the radiative field, that in particular circumstances cannot be neglected. • Consideration of the radiative term brings to a potentially rich and powerful theroretical tool. • New kinds of many-body, non-local interactions are possible even at high temperature (biology). Although all that seems very promising, the theory is still in a preliminary stage and a large effort must be made before these ideas be universally accepted

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