Negative magnetoresistance temperature dependence induced by current-pumped nuclear spin polarization at the $\ensuremath{\nu}=\frac{2}{3}$ quantum Hall state

Negative magnetoresistance temperature dependence induced by current-pumped nuclear spin polarization at the $ν = \frac{2}{3}$ quantum Hall state

Shibun Tsuda, Minh-Hai Nguyen, Daiju Terasawa, Akira Fukuda, and Anju Sawada

Phys. Rev. B 93, 125426 – Published 22 March 2016

Abstract

We investigate the huge longitudinal resistance (HLR) at which the magnetoresistance of the $ν = \frac{2}{3}$ fractional quantum Hall state (QHS) is increased with dynamic nuclear spin polarization. We measure the magnetoresistance temperature dependence in the resistively saturated HLR by increasing the temperature of the sample rapidly in order to prevent relaxation of the nuclear spin polarization. The obtained results indicate that the magnetoresistance decreases as the temperature increases. The Hall resistance in the HLR is also measured and found to exhibit a plateau close to a quantized value. We discuss the negative magnetoresistance temperature dependence with a stripe-shaped domain state deformed by the nuclear spin polarization.

Received 31 May 2015
Revised 2 February 2016

DOI:https://doi.org/10.1103/PhysRevB.93.125426

Physics Subject Headings (PhySH)

Fractional quantum Hall effect

Quantum wells

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Shibun Tsuda^1,*, Minh-Hai Nguyen^1,†, Daiju Terasawa², Akira Fukuda², and Anju Sawada³

¹Department of Physics, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan
²Department of Physics, Hyogo College of Medicine, Nishinomiya 663-8501, Japan
³Research Center for Low Temperature and Materials Sciences, Kyoto University, Kyoto 606-8501, Japan

^*shibun@scphys.kyoto-u.ac.jp
^†Present address: Department of Physics, Cornell University, Ithaca, New York 14853.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 93, Iss. 12 — 15 March 2016

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
(a) Plot of $R_{x x}$ versus $ν$ in the vicinity of the $ν = \frac{2}{3}$ unpolarized QHS. (b) Plot of $R_{x x}$ versus $ν$ in the region of $ν = \frac{2}{3}$ QHS, including the phase transition point between the spin polarized and unpolarized states. The thick red (blue dotted) line represents a fast sweep of $d ν / d t = 1 \times 10^{- 2} s^{- 1}$ from a lower (higher) to a higher (lower) $ν$ , which is realized by changing the electron density at a current of 5 nA. The maximum $R_{x x}$ (indicated by the up arrow) corresponds to the phase transition point. The spin polarized and unpolarized $ν = \frac{2}{3}$ QHSs are observed at the left and right sides of the maximum, respectively. The thin red (broken blue) line represents a slow $ν$ sweep of $d ν / d t = 1 \times 10^{- 4} s^{- 1}$ in the increasing (decreasing) direction at a current of 30 nA. We find a clear hysteresis in $R_{x x}$ . (c) Time evolution of $R_{x x}$ at the $ν = 0.65$ point and for a current of 60 nA. After pumping, decreasing the current to 1 nA yields an increase in $R_{x x}$ of a factor of 2 (blue square point). (d) Time evolution of $R_{x x}$ of the HLR and thermometer temperature $T_{thermo}$ with the addition of a heating power of 1 mW for 50 s. The measuring current for $R_{x x}$ is 1 nA. The red solid and black dotted lines represent the values of $R_{x x}$ and $T_{thermo}$ , respectively. (The green dotted lines and points A–E relate to Fig. 3.)
Reuse & Permissions
Figure 2
(a) Time evolution of $R_{x x}$ at $ν = \frac{1}{3}$ QHS with additional heating power of 1 mW over 50 s. The filling factor is offset slightly from $ν = \frac{1}{3}$ so that the temperature sensitivity of the magnetoresistance remains high at low temperatures [point X, inset of (c)]. The measuring current is 1 nA. The red solid and blue broken lines represent different data obtained by repeating the same procedure. The two lines are in perfect agreement with each other. (b) Relationship between $R_{x x}$ and the sample temperature $T_{sample}$ at $ν = \frac{1}{3}$ QHS under thermal equilibrium. (c) $T_{sample} (t)$ obtained from (a) and (b). (d) $T_{sample}$ dependence of $R_{x x}$ at 1 nA. The blue circles denote the QHS data before DNSP, and the red squares denote the data after DNSP for an ac of 60 nA at 37.7 Hz. Notably, the data after DNSP exhibit a negative temperature dependence.
Reuse & Permissions
Figure 3
(a) Time evolution of $R_{x x}$ in HLR for three different heating durations (0, 27, and 50 s) at a measuring current of 1 nA after 60 nA pumping for 1800 s. Long-term pumping is used to reduce the spin diffusion effect [13]. (b) $T_{thermo}$ evolution.
Reuse & Permissions
Figure 4
$R_{x x}$ (left axis) and $R_{x y}$ (right axis) before and after DNSP as functions of $ν$ for measuring currents of (a) 5 nA and (b) 60 nA. The broken vertical line indicates the value of $ν$ at which DNSP is induced.
Reuse & Permissions
Figure 5
Temperature dependence of longitudinal conductivity $σ_{x x}$ at $ν = \frac{1}{3}$ QHS and for HLR at $ν = \frac{2}{3}$ QHS. The black solid line and red dots correspond to the $ν = \frac{1}{3}$ QHS and HLR at $ν = \frac{2}{3}$ QHS, respectively. The longitudinal conductivity is obtained as $σ_{x x} = ρ_{x x} / (ρ_{x x}^{2} + ρ_{x y}^{2})$ .
Reuse & Permissions
Figure 6
Model of HLR state construction. (a) Initial domain structure. The left side is the edge of the sample. The red squares indicate disorder and the yellow circles are the puddle domains constructed from the polarized QHS affected by the disorder potential. We assume that the electrons enter the puddle domain from position A and exit the domain at the B or $B^{'}$ position. The black solid arrows indicate the case of the upper direction ac current, and the red dotted arrows indicate the reverse case. The electron flips the nuclear spin to the magnetic field direction (black closed circle) at A and to the direction opposite the magnetic field (black cross) at B and $B^{'}$ . (b) From the nuclear polarization, the puddle domain deforms the shape shown in the figure. (c) The puddle domain connects with neighboring puddle domains. (d) The puddle domains connect with each other, forming a stripe-shaped structure. (e) Schematic diagram of the Hall bar in the HLR state.
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Negative magnetoresistance temperature dependence induced by current-pumped nuclear spin polarization at the $ν = \frac{2}{3}$ quantum Hall state

Shibun Tsuda, Minh-Hai Nguyen, Daiju Terasawa, Akira Fukuda, and Anju Sawada

Phys. Rev. B 93, 125426 – Published 22 March 2016

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review B

covering condensed matter and materials physics

Negative magnetoresistance temperature dependence induced by current-pumped nuclear spin polarization at the ν=23 quantum Hall state

Shibun Tsuda, Minh-Hai Nguyen, Daiju Terasawa, Akira Fukuda, and Anju Sawada

Phys. Rev. B 93, 125426 – Published 22 March 2016

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Negative magnetoresistance temperature dependence induced by current-pumped nuclear spin polarization at the $ν = \frac{2}{3}$ quantum Hall state