Ferroelectric switching of a two-dimensional metal

Fei, Zaiyao; Zhao, Wenjin; Palomaki, Tauno; Sun, Bosong; Miller, Moira K.; Zhao, Zhiying; Yan, Jiaqiang; Xu, Xiaodong; Cobden, David

doi:10.1038/s41586-018-0336-3

Cited by 760 publications

(678 citation statements)

References 31 publications

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“…the weak van der Waals interlayer couplings, makes the device easy to fabricate. In particular, boundary effect caused by the lattice mismatching can be reduced greatly if the device is fabricated by stacking 2D materials [46,47].…”

Section: Discussionmentioning

confidence: 99%

In-Plane Ferroelectric Tunnel Junction

et al. 2019

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The ferroelectric material is an important platform to realize non-volatile memories. So far, existing ferroelectric memory devices utilize out-of-plane polarization in ferroelectric thin films. In this paper, we propose a new type of random-access memory (RAM) based on ferroelectric thin films with the in-plane polarization called "in-plane ferroelectric tunnel junction". Apart from nonvolatility, lower power usage and faster writing operation compared with traditional dynamic RAMs, our proposal has the advantage of faster reading operation and non-destructive reading process, thus overcomes the write-after-read problem that widely exists in current ferroelectric RAMs. The recent discovered room-temperature ferroelectric IV-VI semiconductor thin films is a promising material platform to realize our proposal.To meet the daily increasing demands of modern electronic devices, especially of portable devices, memories with low energy consumption and high performance are highly desired. The current commercial dynamic random-access memories (DRAM) are volatile, which consume a large amount of energy to refresh the stored data in order to prevent leakage from the capacitor. To reduce the energy consumption, a non-volatile memory might be the ultimate solution [1,2].The ferroelectric material has been proposed to be an ideal candidate for non-volatile memories due to its electric switchable bistable ground states since 1952 [3], and ferroelectricity based non-volatile memories have been developed rapidly in the past several decades [4,5].Depending on the readout mechanism, ferroelectric non-volatile memories can be roughly classified into two generations. The first generation of ferroelectric RAM (FeRAM) uses polarized charges in the ferroelectric capacitor to represent the data [6][7][8]. As a result, discharging the capacitor to measure the polarized charge destroys the stored data, and the capacitor needs to be recharged after the reading operation. Limited by the destructive reading process, the ferroelectric size effects [9, 10] and various practical issues such as fatigue [11] and imprint [12], the market of FeRAM remains relatively small.To overcome the destructive readout problem, the second generation of ferroelectric tunnel junction (FTJ) is proposed to probe the ferroelectric polarization using the tunneling electroresistance effect [13][14][15]. The basic structure of the FTJ is a metal-ferroelectric-metal junction, where the tunneling potential barrier is determined by the out-of-plane polarization in the ferroelectric layer. In this way, the FTJ realizes bistable resistance states. The major challenge of realizing FTJ is to fabricate ultrathin ferroelectric films so that the tunneling current surpasses the threshold of peripheral amplifiers. The depolarization field induced by the out-of-plane polarization dramatically suppresses the ferroelectric critical temperature or even destroys the ferroelectricity when the films are too thin [16][17][18][19].In this work, we propose a new type of ferroelec-tric memo...

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Section: Discussionmentioning

confidence: 99%

In-Plane Ferroelectric Tunnel Junction

et al. 2019

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“…It has no inversion symmetry [28,29], while monolayers require gating to break inversion symmetry. It exhibits a spontaneous out-of-plane electric polarization [30], which can help tuning spin-orbit coupling through gating.…”

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confidence: 99%

Band Signatures for Strong Nonlinear Hall Effect in Bilayer WTe2

et al. 2018

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Unconventional responses upon breaking discrete or crystal symmetries open avenues for exploring emergent physical systems and materials. By breaking inversion symmetry, a nonlinear Hall signal can be observed, even in the presence of time-reversal symmetry, quite different from the conventional Hall effects. Low-symmetry two-dimensional materials are promising candidates for the nonlinear Hall effect, but it is less known when a strong nonlinear Hall signal can be measured, in particular, its connections with the band-structure properties. By using model analysis, we find prominent nonlinear Hall signals near tilted band anticrossings and band inversions. These band signatures can be used to explain the strong nonlinear Hall effect in the recent experiments on two-dimensional WTe2. This Letter will be instructive not only for analyzing the transport signatures of the nonlinear Hall effect but also for exploring unconventional responses in emergent materials.

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“…We can now obtain the complete expression for the long-wavelength Hamiltonian by combining Eqs. (35), (42) and Eqs. (6), (22).…”

Section: B Electrostatic Energy: Expansion To Higher Ordersmentioning

confidence: 99%

Thermal fluctuations in crystalline membranes with long-range dipole interactions

Mauri¹,

Katsnelson²

2020

Annals of Physics

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We study the effects of long-range electrostatic interactions on the thermal fluctuations of freestanding crystalline membranes exhibiting spontaneous electric polarization directed at each point along the local normal to the surface. We show that the leading effect of dipole-dipole interactions in the long-wavelength limit consists in renormalizations of the bending rigidity and the elastic coefficients. A completely different result was obtained in the case of scalar two-point interactions decaying as |R| −3 , where |R| is the distance. In the latter case, which was addressed in previous theoretical research, the energy of long-wavelength bending fluctuations is controlled by power-law interactions and it scales with the wavevector q as |q| 3 , leading to a modified large-distance behaviour of correlation functions. By contrast, in the case of dipole interactions, the |q| 3 dependence of the bending energy vanishes. Non-local terms generated by the expansion of the electrostatic energy are suppressed in the limit of small wavevectors. This suggests that the universal scaling behaviour of elastic membranes holds even in presence of dipole interactions. At the same time, the shift of the Lamé coefficients and the bending rigidity induced by electrostatic interactions can be quantitatively important for two-dimensional materials with a permanent out-of-plane polarization.

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Ferroelectric switching of a two-dimensional metal

Cited by 760 publications

References 31 publications

In-Plane Ferroelectric Tunnel Junction

In-Plane Ferroelectric Tunnel Junction

Band Signatures for Strong Nonlinear Hall Effect in Bilayer WTe2

Thermal fluctuations in crystalline membranes with long-range dipole interactions

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