Millimeter-wave spectroscopy of low-dimensional molecular metals in high magnetic fields

Hill, Stephen; Brooks, J. S.; Qualls, J. S.; Burgin, T.; Fravel, B.; Montgomery, L. K.; Sarrao, J.L.; Fisk, Z.

doi:10.1016/s0921-4526(98)00035-0

Cited by 14 publications

(17 citation statements)

References 21 publications

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“…of Reference [1], many of the earlier experiments were seriously flawed, and reliable experiments had to await the development of resonant cavity techniques [63,65,64]. Since such measurements became feasible, only two superconducting salts have yielded cyclotron resonance data.…”

Section: Renormalising Interactionsmentioning

confidence: 99%

“…Since such measurements became feasible, only two superconducting salts have yielded cyclotron resonance data. In α-(BEDT-TTF) 2 NH 4 Hg(SCN) 4 , which is believed to have a simple Fermi surface consisting of a pair of sheets and a closed pocket, a cyclotron resonance corresponding to a mass of 1.9m e was measured [64,65]; this may be compared with an effective mass from magnetic quantum oscillations of 2.5m e [67]. β ′′ -(BEDT-TTF) 2 SF 5 CH 2 CF 2 SO 3 , again with a Fermi surface believed to consist of a single pocket and a pair of sheets (but see Reference [66]), exhibited a cyclotron resonance corresponding to a mass of 2.2m e [31] (see Figure 9) the effective mass from Shubnikovde Haas oscillations is 1.9m e [68].…”

Section: Renormalising Interactionsmentioning

confidence: 99%

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Quasi-two-dimensional organic superconductors: A review

Singleton¹,

Mielke²

2002

Contemporary Physics

180

194

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Abstract. We present a review of quasi-two-dimensional organic superconductors. These systems exhibit many interesting phenomena, including reduced dimensionality, strong electron-electron and electron-phonon interactions and the proximity of antiferromagnetism, insulator states and superconductivity. Moreover, it has been possible to measure the electronic bands of many of the organics in great detail, in contrast to the situation in other well-known systems in which similar phenomena occur. We describe the crystal structure and normal-state properties of the organics, before presenting the experimental evidence for and against exotic superconductivity mediated by antiferromagnetic fluctuations. Finally, three instances of field-induced unconventional superconductivity will be described.

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Section: Renormalising Interactionsmentioning

confidence: 99%

Section: Renormalising Interactionsmentioning

confidence: 99%

Quasi-two-dimensional organic superconductors: A review

Singleton¹,

Mielke²

2002

Contemporary Physics

180

194

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“…However, it turns out that for studies of highly anisotropic conductors, two convenient locations are sufficient for most experiments utilizing TE01n modes. 8,9,28 In the "end plate" configuration, the sample is placed on the blank cavity end plate, exactly half way between the cavity axis and its perimeter, as shown in Fig. 9a.…”

Section: Sample Positioning and Sample Rotationmentioning

confidence: 99%

“…In order to a) maximize sensitivity, and b) achieve the required control over the electromagnetic field distribution in the vicinity of the sample, we utilize an enclosed cavity perturbation technique (section II-B). 8,9 The wide frequency coverage and outstanding dynamic range (signal-to-noise) are achieved using a Millimeter-wave Vector Network Analyzer (MVNA) 10,11,12 as a source and detector (see section II-A). The resulting instrumentation offers unique experimental possibilities in the area of metals physics in high magnetic fields.…”

Section: Introductionmentioning

confidence: 99%

Instrumentation for millimeter-wave magnetoelectrodynamic investigations of low-dimensional conductors and superconductors

Mola

Hill

Goy³

et al. 2000

Review of Scientific Instruments

153

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We describe instrumentation for conducting high sensitivity millimeter-wave cavity perturbation measurements over a broad frequency range (40 − 200 GHz) and in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source and phase sensitive detector (8 − 350 GHz), enabling simultaneous measurements of the complex cavity parameters (resonance frequency and Q−value) at a rapid repetition rate (∼ 10 kHz). We discuss the principal of operation of the MVNA and the construction of a probe for coupling the MVNA to various cylindrical resonator configurations which can easily be inserted into a high field magnet cryostat. We also present several experimental results which demonstrate the potential of the instrument for studies of low-dimensional conducting systems.

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“…In the absence of SOC, but retaining inversion symmetry, ∆ eff ∼ 0, and I α is expected to vanish at all fields. Nonetheless, F α oscillations are observed in κ-phase salts, often with I α I β in ET salts [40,42,43] and I α I β in Se-based BETS salts [44][45][46]. Assuming that ∆ eff arises primarily from SOC, we expect the ratio of breakdown fields…”

mentioning

confidence: 96%

Importance of spin-orbit coupling in layered organic salts

2017

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We investigate the spin-orbit coupling (SOC) effects in α-and κ-phase BEDT-TTF and BEDT-TSF organic salts. Contrary to the assumption that SOC in organics is negligible due to light C, S, H atoms, we show the relevance of such an interaction in a few representative cases. In the weakly correlated regime, SOC manifests primarily in the opening of energy gaps at degenerate band touching points. This effect becomes especially important for Dirac semimetals such as α-(ET)2I3. Furthermore, in the magnetic insulating phase, SOC results in additional anisotropic exchange interactions, which provide a compelling explanation for the controversial field-induced behaviour of the quantum spin-liquid candidate κ-(ET)2Cu2(CN)3. We conclude by discussing the importance of SOC for the description of low-energy properties in organics.Layered organic materials have long served as ideal systems for studying complex physical phenomena such as the interplay between charge and spin order, unconventional superconductivity, and, exotic phases emerging from strong electronic correlations [1][2][3][4]. In these systems, high compressibility and synthetic versatility allows fine tuning of the underlying interactions via physical and chemical pressure, thus providing access to many different ground states. For example, significant evidence has recently emerged for a quantum spin liquid (QSL) state in a number of triangular-lattice organics,However, the appearance of very small energy gaps, and field-induced anomalies in the former material remain essentially unexplained. Likewise, interest has recently grown in the α-phase materials α-(ET) 2 I 3 [10] and α-(BETS) 2 I 3 [11]. The former material has been argued to form, under pressure, a zero gap semimetal (ZGS) with the Fermi energy located at the intersection of a pair of tilted Dirac cones [10,12,13]. However, the low-energy electronic and magnetic response shows significant departure from theoretical expectations for simple Dirac systems [14,15]. An unexplored aspect is the effect of spin-orbit coupling (SOC) in these systems.For (inorganic) magnetic insulators, strong SOC may generate large anisotropic magnetic interactions, associated with exotic spin-liquid states discussed e.g. for the iridates and α-RuCl 3 [16][17][18][19][20][21][22]. In weakly correlated systems such as BiSb, Bi 2 Te 3 , etc. [23][24][25][26], SOC tends to open a gap in the bulk, and may lead to nontrivial band topology and associated exotic edge states. Such effects have rarely been considered for the organic ET salts, as the light C, S, H atoms provide only moderate SOC. Nonetheless, it is known that SOC plays a dominant role in the spin relaxation of graphene [27][28][29] and organic-based semiconductors [30], and may be relatively enhanced for orbitally degenerate systems [31]. Indeed, in this work, we argue, despite a weak relative magnitude, that SOC is relevant for the low-energy properties in selected (representative) organic salts. We discuss as primary examples, the α-phase Dirac semimetals, and κ-phase...

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Millimeter-wave spectroscopy of low-dimensional molecular metals in high magnetic fields

Cited by 14 publications

References 21 publications

Quasi-two-dimensional organic superconductors: A review

Quasi-two-dimensional organic superconductors: A review

Instrumentation for millimeter-wave magnetoelectrodynamic investigations of low-dimensional conductors and superconductors

Importance of spin-orbit coupling in layered organic salts

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