Обзор

Field Equations

Draft Formulation for the SET Resonance Substrate#

This document provides a working draft of the evolution equations for the Spin (S), Charge (C), and Temperature (T) fields in the resonance‑substrate model. The goal is to define a minimal, testable system that can be implemented in numerical solvers and compared against experimental data.


Quicklinks#


1. Notation and Conventions#

  • Spatial coordinate: (\mathbf{x} \in \mathbb{R}^3)
  • Time: (t \in \mathbb{R})
  • Spin field: (S(\mathbf{x}, t) \in \mathbb{R}^3)
  • Charge field: (C(\mathbf{x}, t) \in \mathbb{R}) (scalar form for baseline model)
  • Temperature field: (T(\mathbf{x}, t) \in \mathbb{R})
  • (\nabla): spatial gradient
  • (\nabla^2): Laplacian
  • (\partial_t): time derivative

2. Spin Field Evolution#

The Spin field encodes local rotational alignment and coherence.

2.1 Baseline Equation#

[ \partial_t S = D_S \nabla^2 S - \gamma_S S + \lambda_{SC} \nabla C - \lambda_{ST} \nabla T ]

Where:

  • (D_S): spin diffusion coefficient
  • (\gamma_S): spin damping coefficient
  • (\lambda_{SC}): coupling of Spin to Charge gradients
  • (\lambda_{ST}): coupling of Spin to Temperature gradients

Interpretation:

  • (D_S \nabla^2 S): smooths spin inhomogeneities
  • (-\gamma_S S): relaxes spin toward zero alignment
  • (\lambda_{SC} \nabla C): aligns spin with charge gradients
  • (-\lambda_{ST} \nabla T): destabilizes spin in high‑T gradients

3. Charge Field Evolution#

The Charge field encodes interaction bias and potential gradients.

3.1 Baseline Equation#

[ \partial_t C = D_C \nabla^2 C - \gamma_C C + \beta_{CS} \nabla \cdot S ]

Where:

  • (D_C): charge diffusion coefficient
  • (\gamma_C): charge relaxation coefficient
  • (\beta_{CS}): coupling of Charge to Spin divergence

Interpretation:

  • (D_C \nabla^2 C): smooths charge gradients
  • (-\gamma_C C): relaxes charge bias
  • (\beta_{CS} \nabla \cdot S): generates or modulates charge bias from spin structure

4. Temperature Field Evolution#

The Temperature field encodes stochastic and dissipative contributions.

4.1 Baseline Equation#

[ \partial_t T = D_T \nabla^2 T - \gamma_T (T - T_0) + \eta_S |S|^2 + \eta_C |\nabla C|^2 ]

Where:

  • (D_T): thermal diffusion coefficient
  • (\gamma_T): relaxation toward background temperature (T_0)
  • (\eta_S): heating from spin activity
  • (\eta_C): heating from charge gradients

Interpretation:

  • (D_T \nabla^2 T): spreads thermal energy
  • (-\gamma_T (T - T_0)): relaxes toward ambient
  • (\eta_S |S|^2): spin‑induced heating
  • (\eta_C |\nabla C|^2): gradient‑induced heating

5. Resonance Envelope Condition#

A resonance envelope is defined as a region where SET gradients exceed a threshold:

[ \mathcal{R}(\mathbf{x}, t) = \left( |\nabla S| + |\nabla C| - \alpha |\nabla T| \right) - \Theta ]

Resonant region:

[ \mathcal{R}(\mathbf{x}, t) > 0 ]

Where:

  • (\alpha): dissipation weighting factor
  • (\Theta): resonance threshold

6. Dimensionless Form (Optional)#

For numerical work, the equations can be non‑dimensionalized by introducing characteristic scales:

  • Length scale (L)
  • Time scale (\tau)
  • Field scales (S_0, C_0, T_0)

Resulting in dimensionless parameters:

  • (\tilde{D}_S, \tilde{D}_C, \tilde{D}_T)
  • (\tilde{\gamma}_S, \tilde{\gamma}_C, \tilde{\gamma}_T)
  • (\tilde{\lambda}{SC}, \tilde{\lambda}{ST}, \tilde{\beta}_{CS}, \tilde{\eta}_S, \tilde{\eta}_C)

A separate note can specify the chosen scaling for a given simulation.


7. Implementation Notes#

  • Discretization: finite difference, finite volume, or spectral methods.
  • Time integration: explicit or implicit schemes (e.g., Runge–Kutta, Crank–Nicolson).
  • Boundary conditions: periodic, Dirichlet, or Neumann, depending on experiment.

These equations are intended as a minimal, testable starting point. Coefficients and coupling terms can be refined based on experimental calibration and further theoretical development.