Along with the thoroughly investigated magnetoresistance under magnetic fields, another important aspect of the transport properties is the electrical field response. According to Ohm’s law, the voltage should be proportional to the current flowing through the sample, with the ratio being the resistance of the conductor. As a result, the current–voltage (I–V) characteristics should be linear, given that the resistance is independent of the electrical field. Under certain circumstances, the I–V characteristics violate Ohm’s law and become non-linear when the electrical field is high enough, given that the resistance is bias dependent. The non-ohmic transport behaviors have been widely observed and studied in metal oxides and organic charge-transfer salts.

We developed a high-speed I–V measurement system under pulsed magnetic fields in Wuhan National High Magnetic Field Center based on the flat-top pulsed magnetic field (FTPMF). To accomplish the I–V measurements during the short flattop of the high field, a single triangle-wave current pulse was applied, as shown in Fig. 1. The first rising part of the continuous current after the trigger was used for the I–V measurements. The sample connection is based on the typical transport measurement based on the four-probe method and illustrated in Fig. 2.

Fig.1 The profile of the continuous current method applied for the I–V measurements during the short flat-top of high field.

Fig.2 The illustration of the sample connection based on the four-probe transport measurements.

In Fig. 3, we show a typical I-V measurement result of the quasi-one-dimensional purple bronze Li_0.9Mo₆O₁₇. At zero field B = 0 T, the I–V curve is obviously non-linear. For the very low current range, the voltage increases linearly with the current until the current reaches around 25 mA. The slope of the I–V curve dramatically decreases and the curve deviates from the linear (dashed line). As the current increases further, the I–V behavior returns to be linear with a much smaller slope compared to the low current regime. The non-linear I–V behavior is reminiscent of the S-like I–V characteristics observed in other one-dimensional CDW systems.

Fig.3 The I–V curves of the sample measured with the flat-top field up to 30 T at 4.2 K. The 50 T data were obtained under a pulsed field without the flat-top. Data are shifted for clarity. The dashed lines are a guideline for the linear I–V transport properties.

Measurement Conditions

Magnetic field: 0-50 T (Flat-top field)

Flat-top duration: 10-100 ms

Measurement Temperature: 1.5-250 K

Sample Type: Single crystal, film

Sample Size: < 4 mm*4mm

Reference

W. Wei et al., The current–voltage measurements under flat-top pulsed magnetic fields for non-ohmic transport study, Review of Scientific Instruments 93, 085102 (2022).

Key Contact

Ming Yang

Email：ming_yang#hust.edu.cn (Please replace # with @)