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Magnetic oscillation spectrum of surface resistance in layered organic compounds

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Physica Scripta
Authors:
Danica Krstovska at Saints Cyril and Methodius University of Skopje
Danica Krstovska
Aleksandar Skeparovski at Saints Cyril and Methodius University of Skopje
Aleksandar Skeparovski
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Abstract and Figures

The magnetic quantum oscillations of surface resistance in quasi-two dimensional layered organic conductors have been obtained numerically for a magnetic field parallel to the surface. The resonance fields, which were theoretically calculated in a previous work on surface states, are found to coincide closely to the positions of the maxima in the ∂R/∂B\partial R/\partial B curves. We find that, in quasi-two dimensional organic conductors, the transitions between the adjacent surface states are the most present transitions in the sum curve for surface resistance derivative oscillation spectrum. Our results, obtained from the calculations of the oscillation spectra of the individual series and the sum of six series, confirm that the theoretical description of surface states in the anisotropic organic conductors is essentially correct in its numerical aspects. These studies will be very helpful for analyzing and explaining the experimental curves and for their comparison with the theoretical results. Since there are yet no experimental data on surface impedance oscillations in quasi-two dimensional organic conductors with this work we would like to shed new light on this problem in order to motive new research in that direction mostly because of a need of such studies for a possible utilization of surface phenomena in various scientific applications, especially, for possible applications in various organic devices as well as for construction of new ones.
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Phys. Scr. 98 (2023)035816 https://doi.org/10.1088/1402-4896/acb85f
PAPER
Magnetic oscillation spectrum of surface resistance in layered
organic compounds
D Krstovska
∗
and A Skeparovski
Ss. Cyril and Methodius University, Faculty of Natural Sciences and Mathematics, Arhimedova 3, 1000 Skopje, Macedonia
∗
Author to whom any correspondence should be addressed.
E-mail: danica@pmf.ukim.mk
Keywords: quasi-two dimensional organic conductors, surface resistance, quantum oscillations, resonance spectrum, surface states
Abstract
The magnetic quantum oscillations of surface resistance in quasi-two dimensional layered organic
conductors have been obtained numerically for a magnetic field parallel to the surface. The resonance
fields, which were theoretically calculated in a previous work on surface states, are found to coincide
closely to the positions of the maxima in the ∂R/∂Bcurves. We find that, in quasi-two dimensional
organic conductors, the transitions between the adjacent surface states are the most present transitions
in the sum curve for surface resistance derivative oscillation spectrum. Our results, obtained from the
calculations of the oscillation spectra of the individual series and the sum of six series, confirm that the
theoretical description of surface states in the anisotropic organic conductors is essentially correct in
its numerical aspects. These studies will be very helpful for analyzing and explaining the experimental
curves and for their comparison with the theoretical results. Since there are yet no experimental data
on surface impedance oscillations in quasi-two dimensional organic conductors with this work we
would like to shed new light on this problem in order to motive new research in that direction mostly
because of a need of such studies for a possible utilization of surface effects in the existing organic
devices.
1. Introduction
The first experimental observation of the surface impedance oscillations in normal state of metals and in weak
magnetic fields was realized by Khaikin [1]. Detailed theoretical calculations of the effect have shown that it is a
quantum mechanical effect as the observed microwave surface impedance oscillations arise as a result of the
resonant transitions between surface quantum states. These states correspond to the classical electron
trajectories skipping along the surface. The skipping electrons move along open trajectories near the surface and
in a presence of a magnetic field their motion is periodic in the direction perpendicular to the surface. Due to
quantization of their periodic motion the corresponding electron energy spectrum is discrete [2]. Further
studies have shown that the theoretical calculations of the surface impedance oscillation spectrum are in a very
good agreement with the experimentally obtained curves [3]. Also, it was shown that the position of the
resonances in the experimental curves coincide very closely to the theoretically obtained values for the resonance
fields [4].
The electromagnetic response of a conducting material, in its normal and superconducting state, is
described by a complex surface impedance, Z=R+iX where Ris the surface resistance and Xis the surface
reactance, respectively. In the experiments, the measured quantity is the derivative of real part of the surface
impedance, i.e., measurements yield ∂R/∂Bas a function of the magnetic field. This is because the absorption
signal is phase detected and the output of the phase detector is the derivative with respect to magnetic field of the
absorption. The first theory for the surface impedance oscillations is given by Koch [5]. Resonant transitions
between the surface electronic states appear as resonances (peaks)in the oscillation spectrum of ∂R/∂B,
similarly to the cyclotron resonances which are a result of the transitions between Landau levels of volume
electrons. The most important part for interpreting the experimentally observed ∂R/∂Bcurves is the calculation
RECEIVED
12 October 2022
REVISED
15 January 2023
ACCEPTED FOR PUBLICATION
1 February 2023
PUBLISHED
14 February 2023
© 2023 IOP Publishing Ltd
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