C.L. Kane and E.J. Mele, PRL 95, 226801 (2005)

B.A. Bernevig and S.C. Zhang, PRL 96, 106802 (2006)

40 60 80 100 120 140-100

-50

0

50

100

Eg

ap / e

V E1

H4

H3

H1

dQW

/ Å

E2

H2

HgTe QW

B.A. Bernevig, T. L. Hughes, and S. C. Zhang, Science 314, 1757 (2006)

M. König et al., Science 318, 766 (2007); M. König et al., JPSJ 77, 031007 (2008);

A. Roth et al., Science 325, 294 (2009)

-2.0 -1.5 -1.0 -0.5 0.010

2

103

104

105

106

G = 2 e2/h

Rxx /

Vg / V

45 Å

80 Å

A. Roth et al., Science 325, 294 (2009); J. Maciejko et al., PRL 102, 256803 (2009)

M. Topinka et al., Nature 410, 183 (2001); M. Jura et al., Nat. Phys 3, 841 (2007)

coarse

positioning

(several mm)

piezo-electric

scanner

(several μm)

AFM tip

Sample

M. Topinka et al., Nature 410, 183 (2001); M. Jura et al., Nat. Phys 3, 841 (2007)

z (nm)400

0

2 μm

2 μm

Vtip = -8 V

G(e2/h)+0.1

-0.1

G (

e2/h

)

y (μm)

-8 V -4 V +4 V-2 V +2 V0 V-6 V

-0.1 +0.1

G (e2/h)

mesa

-8 V +4 V

mesa

50 μm

-8 V +4 V-10 V +5 V

mesa

50 μm

-8 V +4 V-10 V +5 VG(-10 V)

– G(+5 V)