Aharonov-Bohm effect in scattering of high-energy particles

Quantum-mechanical scattering of coherent high-energy charged particles by a magnetic vortex is considered. The vortex core is assumed to be impermeable to scattered particles, and effects of its transverse size are taken into account. The limit of high energies of scattered particles corresponds to...

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Published in:Вопросы атомной науки и техники
Date:2012
Main Authors: Sitenko, Yu.A., Vlasii, N.D.
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Language:English
Published: Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine 2012
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Cite this:Aharonov-Bohm effect in scattering of high-energy particles / Yu.A. Sitenko, N.D. Vlasii // Вопросы атомной науки и техники. — 2012. — № 1. — С. 121-124. — Бібліогр.: 9 назв. — англ.

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author Sitenko, Yu.A.
Vlasii, N.D.
author_facet Sitenko, Yu.A.
Vlasii, N.D.
citation_txt Aharonov-Bohm effect in scattering of high-energy particles / Yu.A. Sitenko, N.D. Vlasii // Вопросы атомной науки и техники. — 2012. — № 1. — С. 121-124. — Бібліогр.: 9 назв. — англ.
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description Quantum-mechanical scattering of coherent high-energy charged particles by a magnetic vortex is considered. The vortex core is assumed to be impermeable to scattered particles, and effects of its transverse size are taken into account. The limit of high energies of scattered particles corresponds to the quasiclassical limit, and we show that in the scattering the Aharonov-Bohm effect persists in this limit owing to the Fraunhofer diffraction in the forward direction. The issue of the experimental detection of the Fraunhofer diffraction peak and the Aharonov-Bohm effect in the quasiclassical limit is discussed. Рассматривается квантово-механическое рассеяние высокоэнергетических заряженных частиц магнитным вихрем. Ядро вихря предполагается непроницаемым для рассеиваемых частиц, и учитываются эффекты его поперечных размеров. Предел высоких энергий рассеиваемых частиц соответствует квазиклассическому пределу, и мы показываем, что эффект Ааронова-Бома в рассеянии в этом пределе выживает благодаря дифракции Фраунгофера в направлении вперед. Обсуждаются вопросы экспериментального детектирования пика Фраунгоферовой дифракции и эффекта Ааронова-Бома в квазиклассическом пределе. Розглядається квантово-механічне розсіяння високоенергетичних заряджених частинок магнітним вихором. Припускається, що ядро вихора є непроникним для розсіюваних частинок, та враховуються ефекти його поперечних розмірів. Границя високих енергій розсіюваних частинок відповідає квазікласичній границі, і ми показуємо, що ефект Ааронова-Бома в розсіянні в цій границі виживає завдяки дифракції Фраунгофера в напрямку вперед. Обговорюються питання експериментального детектування піка Фраунгоферової дифракції та ефекта Ааронова-Бома в квазікласичній границі.
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fulltext AHARONOV-BOHM EFFECT IN SCATTERING OF HIGH-ENERGY PARTICLES Yu.A. Sitenko1∗and N.D. Vlasii1,2 1Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine, 03680, Kyiv, Ukraine 2Physics Department, Taras Shevchenko National University of Kyiv, 01601, Kyiv, Ukraine (Received November 2, 2011) Quantum-mechanical scattering of coherent high-energy charged particles by a magnetic vortex is considered. The vortex core is assumed to be impermeable to scattered particles, and effects of its transverse size are taken into account. The limit of high energies of scattered particles corresponds to the quasiclassical limit, and we show that in the scattering the Aharonov-Bohm effect persists in this limit owing to the Fraunhofer diffraction in the forward direction. The issue of the experimental detection of the Fraunhofer diffraction peak and the Aharonov-Bohm effect in the quasiclassical limit is discussed. PACS: 03.65.Nk, 03.65.Ta, 41.75.Fr, 75.70.Kw 1. INTRODUCTION Starting from its discovery in 1959, the Aharonov- Bohm effect [1] is considered in the framework of two somewhat different, although closely related, setups. The first one concerns the fringe shift in the interfer- ence pattern due to two coherent particle beams un- der the influence of the impermeable magnetic vortex placed between the beams. The second one deals with scattering of a particle beam directly on an imperme- able magnetic vortex. All experiments are performed in the first setup, though the second setup is more elaborate from the theoretical point of view. The reason of this somewhat a paradoxical situation lies in the simple fact that the efforts in the elaboration of scattering theory for the Aharonov-Bohm effect were mostly concentrated on the case of long-wavelength scattered particles, when the transverse size of the impermeable magnetic vortex was neglected. Since a direct scattering experiment is hard to perform with long-wavelength (slow-moving) particles, thus elabo- rated theory remained actually unverified. The aim of the present paper is to extend the theory to the case of short-wavelength (fast-moving) particles and to reach the realm where the experimental verifica- tion is quite feasible (see also [2–4]). 2. DOUBLE-SLIT INTERFERENCE EXPERIMENT But, first, let us recall briefly the setup which is conventionally used for the verification of the Aharonov-Bohm effect (see, e.g., [5, 6]). It involves the observation of the interference patterns result- ing from the two coherent electron beams bypassing from different sides an impermeable magnetic vor- tex which is orthogonal to the plane defined by the beams. This is a so called double-slit interference ex- periment, although in reality an electrostatic biprism is used to bend the beams and to direct them on the detection screen. Let the detection screen be parallel to the screen with slits, L be the distance between the screens, and d be the distance between the slits; otherwise, in the biprism setting, the line connecting images of a source is parallel to the detection screen, L is the distance between the line and the screen, and d is the distance between the images. The in- terference pattern on the detection screen consists of equally spaced fringes which are in the same direction as the magnetic vortex, I(y) = 4I0(y) cos2 [( yd λL + Φ Φ0 ) π ] , (1) where y is the coordinate which is orthogonal to the fringes on the detection screen (y = 0 corresponds to the point which is symmetric with respect to the slits), I0(y) is the intensity in the case when either of the slits is closed, λ is the electron wavelength, Φ is the flux of the impermeable magnetic vortex placed just after the screen with slits (otherwise, after the biprism), Φ0 = hce−1 is the London flux quantum. Intensity I(y) (1) is oscillating with period Δy = λLd−1 (2) and the enveloping function given by 4I0(y) which is a Gaussian centred at y = 0. At the centre of the detection screen one gets I(0) = 4I0(0) cos2 ( Φ Φ0 π ) . (3) If L� d and λ, then one can use dimensionless (an- gular) variable ϕ = y/L. The period of oscillations ∗Corresponding author E-mail address: yusitenko@bitp.kiev.ua PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2012, N 1. Series: Nuclear Physics Investigations (57), p. 121-124. 121 in this variable is Δϕ = λd−1. (4) Evidently, the period of oscillation decreases with the decrease of wavelength λ. The distance resolu- tion of the detector should be at least as high as 1 2Δy, that is why the observation of the interference pattern becomes more complicated in the short-wavelength limit. Since the enveloping function takes a form of a narrow peak in this limit, it is appropriate to define the visibility of the central point V = ∣∣I(0) − I (± 1 2Δy )∣∣ I(0) + I (± 1 2Δy ) . (5) Assuming I0 (− 1 2Δy ) = I0 ( 1 2Δy ) , one finds immedi- ately V = (6) = ∣∣∣I0(0)−I0 ( 1 2Δy ) + [ I0(0)+I0 ( 1 2Δy )] cos ( 2 Φ Φ0 π )∣∣∣ I0(0)+I0 ( 1 2Δy ) + [ I0(0)−I0 ( 1 2Δy )] cos ( 2 Φ Φ0 π ) . 3. DIRECT SCATTERING EXPERIMENT We start with the Schrödinger equation for the wave function describing the stationary scattering state Hψ(r, ϕ) = h̄2k2 2m ψ(r, ϕ), (7) where m is the particle mass and k is the absolute value of the particle wave vector (k = 2π/λ); the im- permeable magnetic vortex is assumed to be directed orthogonally to the plane with polar coordinates r and ϕ, and we confine ourselves to the particle mo- tion in this plane, since the motion along the vortex is free. Out of the vortex core the Schrödinger hamil- tinian takes form H = − h̄2 2m [ r−1∂rr∂r + r−2 ( ∂ϕ − iΦΦ−1 0 )2 ] , (8) and we impose condition lim r→∞ eikrψ(r, ±π) = 1, (9) signifying that the incident wave comes from the far left; the forward direction is ϕ = 0, and the backward direction is ϕ = ±π. Without a loss of generality we assume that the vortex has a shape of cylinder of radius rc and impose the Robin boundary condition on the wave function: {[cos(ρπ) + rc sin(ρπ)∂r ]ψ(r, ϕ)}|r=rc = 0. (10) The solution to (7) with Hamiltonian (8), which sat- isfies (9) and (10), takes the following form ψ(r, ϕ) = ∑ n∈Z einϕei(|n|− 1 2 |n−μ|π) [ J|n−μ|(kr) −Υ(ρ) |n−μ|(krc)H (1) |n−μ|(kr) ] , (11) where Z is the set of integer numbers, μ = ΦΦ−1 0 , Jα(u) and H(1) α (u) are the Bessel and first-kind Han- kel functions of order α, and Υ(ρ) α (u) = Jα(u) + tan(ρπ)u∂uJα(u) H (1) α + tan(ρπ)u∂uH (1) α (u) . (12) Thus, wave function (11) consists of two parts: the one which will be denoted by ψ0(r, ϕ) is independent of rc, and the other one which will be denoted by ψc(r, ϕ) is dependent on rc. Taking the asymptotics of the first part at large distances from the vortex, one can get (see [7]) ψ0(r, ϕ) = eikr cos ϕ+iμϕ { cos(μπ) − isgn(ϕ) sin(μπ) × [ 1 − ei( 1 2+ν−μ)ϕerfc ( e−iπ/4 √ 2kr ∣∣∣sin ϕ 2 ∣∣∣)]} , (13) where it is implied that −π < ϕ < π, erfc(z) = 2√ π ∞∫ z du e−u2 is the complementary error function, ν = [[μ]] is the integer part of μ, and sgn(u) ={ 1, u > 0 −1, u < 0 } . In the case √ kr ∣∣sin ϕ 2 ∣∣ � 1, one gets ψ0(r, ϕ) = eikr cos ϕeiμ[ϕ−sgn(ϕ)π]+f0(k, ϕ) ei(kr+π/4) √ r , (14) where f0(k, ϕ) = i ei(ν+ 1 2 )ϕ √ 2πk sin(μπ) sin(ϕ/2) (15) is the scattering amplitude which was first obtained by Aharonov and Bohm [1]. In the case kr � 1 but√ kr ∣∣sin ϕ 2 ∣∣ � 1, one gets ψ0(r, ϕ) = eikr cos(μπ). (16) Taking the large-distance asymptotocs of the rc- dependent part of the wave function, one gets ψc(r, ϕ) = fc(k, ϕ) ei(kr+π/4) √ r , (17) where fc(k, ϕ) = i √ 2 πk ∑ n∈Z einϕei(|n|−|n−μ|π)Υ(ρ) |n−μ|(krc). (18) In the low-energy (long-wavelength) limit amplitude fc (18) is suppressed by powers of krc as compared to amplitude f0 (15); however this limit is not feasible to experimental measurements. In the higt-energy (short-wavelength) limit, amplitude f0 (15) is sup- pressed and wave function ψ0 (13) is actually reduced to an incident wave, eikr cos ϕ, which is distorted by the flux-dependent factors, see first term in (14) and (16). Amplitude fc (18) in this limit is prevailing, and we obtain the corresponding differential cross section, see [2], dσ dϕ = |fc(k, ϕ)|2 = 4rcΔ 1 2krc (ϕ) cos2 ( 1 2 krcϕ+ μπ ) + rc 2 ∣∣∣sin ϕ 2 ∣∣∣ , (19) 122 where Δx(ϕ) = 1 4πx sin2(xϕ) sin2(ϕ/2) (−π < ϕ < π) (20) is a strongly peaked at ϕ = 0 and x � 1 function which can be regarded as a regularization of the an- gular delta-function, lim x→∞Δx(ϕ) = 1 2π ∑ n∈Z einϕ, Δx(0) = x π . (21) Thus, the first term on the right-hard side of (19) describes the forward peak of the Fraunhofer diffrac- tion on the vortex, while the second term describes the classical reflection from the vortex. Using nota- tions of the vortex diameter, d = 2rc, and the particle wavelength, λ = 2π/k, we rewrite (19) in a form sim- ilar to (1): dσ dϕ = 2dΔ dπ 2λ (ϕ) cos2 [( ϕd 2λ + Φ Φ0 ) π ] + d 4 ∣∣∣sin ϕ 2 ∣∣∣ ; (22) the differential cross section of the Fraunhofer diffrac- tion is oscillating with period, cf. (4), Δϕ = 2λd−1. (23) In the strictly forward direction one gets, cf. (3), dσ dϕ ∣∣∣∣ ϕ=0 = d2 λ cos2 ( Φ Φ0 π ) . (24) Defining the visibility of the central point in the dif- ferential cross section as V = |dσ|ϕ=0 − dσ|ϕ=± 1 2Δϕ| dσ|ϕ=0 + dσ|ϕ=± 1 2Δϕ , (25) we get V = ∣∣∣1 − 4 π2 + ( 1 + 4 π2 ) cos ( 2 Φ Φ0 π )∣∣∣ 1 + 4 π2 + ( 1 − 4 π2 ) cos ( 2 Φ Φ0 π ) . (26) The maximal visibility (V = 1) is attained for the flux which is quantized in the units of the Abrikosov vor- tex flux ( Φ = 1 2nΦ0 ) ; the minimal visibility (V = 0) is attained at Φ= { n± 1 4 ± 1 2π arcsin [( 1− 4 π2 ) ( 1+ 4 π2 )−1 ]} Φ0. 4. SUMMARY AND DISCUSSION We have shown that the fringe shift emerging un- der the influence of a magnetic vortex in the diffrac- tion pattern in the forward direction in a direct scat- tering experiment with high-energy particles is com- pletely analogous to that in the interference pattern in a double-slit experiment. It should be emphasized that permeability of the magnetic vortex does not af- fect the diffraction pattern (first term in (22)), only the classical reflection (second term in (22)) is af- fected. The latter circumstance facilitates the obser- vation of the scattering Aharonov-Bohm effect in the quasiclassical limit. Certainly, the Fraunhofer diffraction (i.e. the dif- fraction in almost parallel rays) is a well-known phe- nomenon of wave optics. Poisson was the first who predicted theoretically in the early nineteenth cen- tury the emergence of a spot of brightness in the cen- tre of a shadow of an opaque disc; the prediction was in a contradiction with the laws of geometric (ray) optics. It is curious that Poisson used his prediction as an argument to disprove wave optics: this demon- strates how unexpected and unbelievable was Pois- son’s result at that time. Nevertheless, the bright- ness spot in the centre of the disc shadow was soon observed; the decisive experiments were performed by Arago and Fresnel. The diffraction on the opaque disc bears the name of Poisson, and the brightness spot in the shadow centre bears the name of Arago, see [8]. The same effect persists for scattering of light on an opaque ball and other obstacles. However, in the case of obstacles in the form of a long strip or cylinder, the streak of brightness in the centre of a shadow of such obstacles is elusive to experimental measurements: as is noted in the well-known trea- tise [9], it seems more likely that the measurable quantity is the classical cross section, although the details of this phenomenon depend on the method of measurement. Almost six decades have passed from the time when this assertion was made by Morse and Feshbach, and experimental facilities have improved enormously since then. It is a challenge for exper- imentalists to reconsider the Fraunhofer diffraction on the cylindrical obstacles. In the present paper we draw attention to this long-standing problem by pointing at the circumstances when the detection of the forward diffraction peak will be the detection of the Aharonov-Bohm effect persisting in the quasiclas- sical limit. Acknowledgements The work was supported in part by the Ukrainian- Russian SFFR-RFBR project F40.2/108 “Applica- tion of string theory and field theory methods to non- linear phenomena in low-dimensional systems”. References 1. Y. Aharonov, D. Bohm. Significance of electro- magnetic potentials in the quantum theory // Phys. Rev. 1959, v. 115, p. 485-491. 2. Yu.A. Sitenko, N.D. Vlasii. Diffraction and qua- siclassical limit of the Aharonov-Bohm effect // EPL. 2010, v. 92, 60001, 6 p. 3. Yu.A. Sitenko, N.D. Vlasii. Scattering theory and the Aharonov-Bohm effect in quasiclassi- cal physics // Ann. Phys. (N. Y.) 2011, v. 326, p. 1441-1456. 123 4. Yu.A. Sitenko, N.D. Vlasii. Optical theorem for Aharonov-Bohm scattering // J. Phys. A: Math. Theor. 2011, v. 44, 315301, 16 p. 5. M. Peshkin, A. Tonomura. The Aharonov–Bohm Effect. Berlin: Springer-Verlag, 1989. 6. A. Tonomura. The AB effect and its expanding applications // J. Phys. A: Math. Theor. 2010, v. 43, 354021, 13 p. 7. C.M. Sommerfield, H. Minakata. Aharonov- Bohm and Coulomb scattering near the forward direction // Dynamics of Gauge Fields – Proc. TMU-Yale Symposium, Tokyo, Japan, 1999 / Edited by A. Chodos et al. Tokyo: Universal Academy Press, 2000, p. 81-90. 8. A. Sommerfeld. Optik (Vorlesungen uber The- oretische Physik . Band IV). Wiesbaden, 1950 (Kapitel V, § 35). 9. P.M. Morse, H. Feshbach. Methods of Theoret- ical Physics II. New York: McGraw-Hill, 1953 (Chapter 11, Section 11.2). ������ ���� � ���� � ������ �� ������ ������������ ������ ���� ����� � �� � ������ ����������� �� ����� � �� ����� �� ���� �� ��� � �� �� ��� ���� ��� � ���� ������ ������� ��� ���� �� ��� ���� �� �� ���� �� � �� ���� ��� �� ���� ��� ��� ������� � ���������� ��� ��� � � � � ���� ���� � �� � � � ��� ��� �� ���! ���� ��� ��� ������ � �� ����� � ���� ��������� �� �� �� � ��� � �� � ������ �� �� ��� �� "�� � ���# �� � ���� ��� � �� � �� � � ������ � $��� ��� ��������� %����� � �� � ������� ��� �� � �� &$�������� � �� �� ���� � ��� ����'� � � � ���� ���� ���� %����� � � � ! ��������� � ��� ��� "�� � ���# �� � ������ ������� �� � �� � � � ����� ���� � ���� � ������ � ������ ������� �� ����� �� ���� ����� � �� � ������ � ��� ��(�'� ����� � �� ���)�� � ��) �� ��� � � �� ������ ��� �� ��� ������ � ����)���� ��� � � �� �������(�'� � * �� ��� �� ( � �� ������ �� � ��)������ ������ �� �� ���� ����'� � ��� ! � � � � ���� � ��)�)�� +����� ��� ��� � ��)! � ��)������ ������ � �)�� �)��( ����)���� ����)! ������)� ) �� � ����(� � * � �� "�� � ���# �� � � ��) ��) � �)! ������) ������( ���� �� �������), %����� � �� � ���� ��� �� � �� &$� � ����'� ������ ��� ��� ����'� � � � ������� � �)�� %����� � � � , �������), �� � ��� "�� � ���# �� � ����)�������)! ������)� -./
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institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
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last_indexed 2025-12-07T16:46:32Z
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publisher Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine
record_format dspace
spelling Sitenko, Yu.A.
Vlasii, N.D.
2016-10-10T20:34:58Z
2016-10-10T20:34:58Z
2012
Aharonov-Bohm effect in scattering of high-energy particles / Yu.A. Sitenko, N.D. Vlasii // Вопросы атомной науки и техники. — 2012. — № 1. — С. 121-124. — Бібліогр.: 9 назв. — англ.
1562-6016
PACS: 03.65.Nk, 03.65.Ta, 41.75.Fr, 75.70.Kw
https://nasplib.isofts.kiev.ua/handle/123456789/107009
Quantum-mechanical scattering of coherent high-energy charged particles by a magnetic vortex is considered. The vortex core is assumed to be impermeable to scattered particles, and effects of its transverse size are taken into account. The limit of high energies of scattered particles corresponds to the quasiclassical limit, and we show that in the scattering the Aharonov-Bohm effect persists in this limit owing to the Fraunhofer diffraction in the forward direction. The issue of the experimental detection of the Fraunhofer diffraction peak and the Aharonov-Bohm effect in the quasiclassical limit is discussed.
Рассматривается квантово-механическое рассеяние высокоэнергетических заряженных частиц магнитным вихрем. Ядро вихря предполагается непроницаемым для рассеиваемых частиц, и учитываются эффекты его поперечных размеров. Предел высоких энергий рассеиваемых частиц соответствует квазиклассическому пределу, и мы показываем, что эффект Ааронова-Бома в рассеянии в этом пределе выживает благодаря дифракции Фраунгофера в направлении вперед. Обсуждаются вопросы экспериментального детектирования пика Фраунгоферовой дифракции и эффекта Ааронова-Бома в квазиклассическом пределе.
Розглядається квантово-механічне розсіяння високоенергетичних заряджених частинок магнітним вихором. Припускається, що ядро вихора є непроникним для розсіюваних частинок, та враховуються ефекти його поперечних розмірів. Границя високих енергій розсіюваних частинок відповідає квазікласичній границі, і ми показуємо, що ефект Ааронова-Бома в розсіянні в цій границі виживає завдяки дифракції Фраунгофера в напрямку вперед. Обговорюються питання експериментального детектування піка Фраунгоферової дифракції та ефекта Ааронова-Бома в квазікласичній границі.
The work was supported in part by the UkrainianRussian&#xd; SFFR-RFBR project F40.2/108 “Application&#xd; of string theory and field theory methods to nonlinear&#xd; phenomena in low-dimensional systems”.
en
Bogolyubov Institute for Theoretical Physics, National Academy of Sciences of Ukraine
Вопросы атомной науки и техники
Section B. QED Processes at High Energies
Aharonov-Bohm effect in scattering of high-energy particles
Эффект Ааронова-Бома в рассеянии высокоэнергетических частиц
Ефект Ааронова-Бома в розсіянні високоенергетичних частинок
Article
published earlier
spellingShingle Aharonov-Bohm effect in scattering of high-energy particles
Sitenko, Yu.A.
Vlasii, N.D.
Section B. QED Processes at High Energies
title Aharonov-Bohm effect in scattering of high-energy particles
title_alt Эффект Ааронова-Бома в рассеянии высокоэнергетических частиц
Ефект Ааронова-Бома в розсіянні високоенергетичних частинок
title_full Aharonov-Bohm effect in scattering of high-energy particles
title_fullStr Aharonov-Bohm effect in scattering of high-energy particles
title_full_unstemmed Aharonov-Bohm effect in scattering of high-energy particles
title_short Aharonov-Bohm effect in scattering of high-energy particles
title_sort aharonov-bohm effect in scattering of high-energy particles
topic Section B. QED Processes at High Energies
topic_facet Section B. QED Processes at High Energies
url https://nasplib.isofts.kiev.ua/handle/123456789/107009
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AT sitenkoyua éffektaaronovabomavrasseâniivysokoénergetičeskihčastic
AT vlasiind éffektaaronovabomavrasseâniivysokoénergetičeskihčastic
AT sitenkoyua efektaaronovabomavrozsíânnívisokoenergetičnihčastinok
AT vlasiind efektaaronovabomavrozsíânnívisokoenergetičnihčastinok