Detector backaction on the self-consistent bound state in quantum point contacts

Rapid Communication

Detector backaction on the self-consistent bound state in quantum point contacts

Y. Yoon, M.-G. Kang, T. Morimoto (森本崇弘), L. Mourokh, N. Aoki (青木伸之), J. L. Reno, J. P. Bird, and Y. Ochiai (落合勇一)

Phys. Rev. B 79, 121304(R) – Published 10 March 2009

Abstract

Bound-state (BS) formation in quantum point contacts (QPCs) may offer a convenient way to localize and probe single spins. In this Rapid Communication, we investigate how such BSs are affected by monitoring them with a second QPC, which is coupled to the BS via wave-function overlap. We show that this coupling leads to a unique detector backaction, in which the BS is weakened by increasing its proximity to the detector. We also show, however, that this interaction between the QPCs can be regulated at will by using an additional gate to control their wave-function overlap.

Received 3 February 2009

DOI:https://doi.org/10.1103/PhysRevB.79.121304

Authors & Affiliations

Y. Yoon¹, M.-G. Kang¹, T. Morimoto (森本崇弘)², L. Mourokh³, N. Aoki (青木伸之)⁴, J. L. Reno⁵, J. P. Bird^1,4, and Y. Ochiai (落合勇一)⁴

¹Department of Electrical Engineering, University at Buffalo, The State University of New York, Buffalo, New York 14260-1920, USA
²Advanced Device Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
³Department of Physics, Queens College of CUNY, 65-30 Kissena Boulevard, Flushing, New York 11367, USA
⁴Graduate School of Advanced Integration Science, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan
⁵CINT Science Department, Sandia National Laboratories, P.O. Box 5800, Albuquerque, New Mexico 87185-1303, USA

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Issue

Vol. 79, Iss. 12 — 15 March 2009

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Images

Figure 1
(Color online) (a) Schematic of the resonance when electrons tunnel back and forth between a BS on the swept QPC (foreground) and the detector (background). (b) Device schematic. $G_{1} - G_{8}$ are gates and Ohmic contacts are numbered 1–8. (c) Variation in $G_{d}$ and $G_{s}$ (line with open circles) at 4.2 K. $G_{d}$ is measured by passing current $(I)$ from 1 to 4 and measuring voltage $(V)$ between 2 and 3. $G_{s}$ uses 8 and 5 for $I$ and 7 and 6 for $V$ . Circle in schematic indicates BS location. (d) Same as (c) but with gate $G_{5}$ biased to pinch off the region between $G_{5}$ and $G_{8}$ . (e) ${| q |}^{- 1}$ vs QPC separation. Dotted line is an interpolation between points. Each data point is an average obtained by using different pairs of QPCs to implement equivalent configurations, and the error bars for each point indicate the range of values contributing to the average.Reuse & Permissions
Figure 2
(Color online) Resonance in $G_{d}$ (open symbols) (solid line through symbols denotes fit to Fano form) and variation in $G_{s}$ for different QPC configurations at 4.2 K. The corresponding Fano factor $(q)$ is shown. Circle in schematics indicates where BS is formed. (a) $G_{d}$ : $I$ —1 and 4, $V$ : 2 and 3; $G_{s}$ : $I$ —8 and 5, $V$ : 7 and 6. (b) $G_{d}$ : $I$ —8 and 5, $V$ : 7 and 6; $G_{s}$ : $I$ —1 and 4; $V$ : 2 and 3. (c) $G_{d}$ : $I$ —1 and 4, $V$ : 2 and 3; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7. (d) $G_{d}$ : $I$ —8 and 5, $V$ : 7 and 6; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7. (e) $G_{d}$ : $I$ —1 and 4, $V$ : 2 and 3; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7. (f) $G_{d}$ : $I$ —8 and 5, $V$ : 7 and 6; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7.Reuse & Permissions
Figure 3
(Color online) Resonance in $G_{d}$ (open symbols) (solid line through symbols denotes fit to Fano form) and variation in $G_{s}$ for equivalent QPC configurations at 4.2 K. The corresponding Fano factor $(q)$ is shown. Circle in schematics indicates where BS is formed. (a) $G_{d}$ : $I$ —1 and 8, $V$ : 2 and 7; $G_{s}$ : $I$ —1 and 4, $V$ : 2 and 3. (b) $G_{d}$ : $I$ —1 and 8, $V$ : 2 and 7; $G_{s}$ : $I$ —8 and 5, $V$ : 7 and 6. (c) $G_{d}$ : $I$ —4 and 5, $V$ : 3 and 6; $G_{s}$ : $I$ —8 and 5, $V$ : 7 and 6. (d) $G_{d}$ : $I$ —8 and 5, $V$ : 7 and 6; $G_{s}$ : $I$ —4 and 5, $V$ : 3 and 6.Reuse & Permissions
Figure 4
(Color online) Main panel: temperature dependence of detector-resonance amplitude for gate configurations A and B (indicated on the upper right-hand side). Insets: resonance at different temperatures in the two configurations. Configuration A: $G_{d}$ : $I$ —1 and 4, $V$ : 2 and 3; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7. Configuration B: $G_{d}$ : $I$ —1 and 4, $V$ : 2 and 3; $G_{s}$ : $I$ —1 and 8, $V$ : 2 and 7. Results for configuration A are shown for a measurement excitation of $30 μ V$ (solid line) and $300 μ V$ (line with open symbols).Reuse & Permissions

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