Math 2.0

Quantum theory Definition

Laughlin wavefunction

Builds on Quantum Hall effect

Definition

Consider NN electrons in the plane in a perpendicular magnetic field, and measure lengths in units of the magnetic length ℓB=ℏ/(eB)\ell_B = \sqrt{\hbar/(eB)}. Write the position of electron jj as the complex number zj=xj+iyjz_j = x_j + i y_j. Choose the orientation so that lowest Landau level states are f(z)e−∣z∣2/4f(z) e^{-\abs{z}^2/4} with ff analytic. For an odd integer m≥1m \ge 1, the Laughlin wavefunction is Ψm(z1,…,zN)=∏1≤i<j≤N(zi−zj)m exp⁡(−14∑j=1N∣zj∣2).\Psi_m(z_1, \dots, z_N) = \prod_{1 \le i < j \le N} (z_i - z_j)^m \, \exp\Big(-\frac14 \sum_{j=1}^{N} \abs{z_j}^2\Big). It describes the quantum Hall state at filling fraction ν=1/m\nu = 1/m.

Remarks

The function is antisymmetric: exchanging ziz_i and zjz_j multiplies (zi−zj)m(z_i - z_j)^m by (−1)m=−1(-1)^m = -1 and permutes the other factors. It lies in the lowest Landau level, since its prefactor is a polynomial in the zjz_j. The modulus squared ∣Ψm∣2\abs{\Psi_m}^2 is the Boltzmann weight of a two-dimensional one-component plasma, which shows that the state is a uniform liquid of density 1/(2πm)1/(2\pi m) in these units.

Example: for m=1m = 1, ∏i<j(zi−zj)\prod_{i<j}(z_i - z_j) is, up to sign, the Vandermonde determinant det⁡(zij−1)\det(z_i^{j-1}), so Ψ1\Psi_1 is the Slater determinant of the orbitals zke−∣z∣2/4z^k e^{-\abs{z}^2/4}, 0≤k≤N−10 \le k \le N - 1: the filled lowest Landau level, ν=1\nu = 1.

Non-example: for m=2m = 2 the same formula is symmetric under exchange, so it is not an admissible state of electrons, which are fermions; it describes bosons at ν=1/2\nu = 1/2.

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Further reading

  1. Web https://en.wikipedia.org/wiki/Laughlin_wavefunction
About this page
TagBG0BYJA523
URIm2://BG0BYJA523
Kinddefinition
WritingW0 stub
MSC81V70, 81V27
DefinesLaughlin wavefunction
UsesQuantum Hall effect
Changed3 November 2026

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